Tools, Tips and Tricks
Identification System for Film Holders
A binary numbering pattern for large format sheet film
Today’s roll films, both 35mm and medium format, are marked with the manufacturer’s name, the product name, and the frame numbers. The pre-exposed frame numbers don’t always perfectly match the frames we are exposing, but they still allow us to correlate our exposure records with each individual frame on the roll. This is a service too easily taken for granted, and the benefits of it did not become apparent to me, until I exposed and developed my first sheet film.
Sheet film, in sizes 4x5 inches and up, does not have any pre-exposed markings on it. The only standard identification is a pre-cut notch system, which specifies the manufacturer and the product itself. This system identifies the film in front of you, as Kodak’s TMax-400 for example, and another negative as Ilford’s FP4, but it does not tell you which of your film holders was used during the exposure of a particular negative. However, this is valuable information to a careful photographer, for a couple of reasons.
Not all film holders function with exactly the same results. Their purpose is to hold the sheet film flat at the image plane, within a given tolerance, and to provide a light tight environment, protecting the film while closed. When they get older and begin to wear, they may lose one or both functions and the possible results are unsharp images and light leaks. It would be useful to know, by looking at the ruined negative, which holder failed, so that the culprit can be eliminated or repaired. Luckily, I have never had such a drastic failure, but since I began numbering my film holders, I have discovered that some produce a sharper image than others. A far stronger reason to correlate film holders with individual negatives are the detailed exposure records I keep.
I am in the habit of making precise exposure records. During every photo session I record the shutter speed, aperture, focal length, filtration, reciprocity modifications, subject brightness range, and any other relevant data for every frame or film holder number used. I like to have this data, because it allows me to learn and improve, and it can be interesting reference information in the future. The tedium of recording this data can be a chore, but it is made easier using a simple handheld tape recorder. The data is recorded within seconds and is available for later transcription to my written records, which are then filed with my negatives.
Unfortunately, a limited number of film holders and sorting sheet film by development needs can lead to a loss of the correlation between a particular negative and the related sheet film holder. Here is an example. I own 12 holders allowing for 24 exposures, which is enough for my shooting habits to last me for a day. At the end of the day, the film holders are emptied and the exposed film sheets are stored in separate old film boxes, depending on the suggested development compensations, from N-3 to N+3. At this point, the holders are loaded with fresh film, so they are ready for the next day. After the film is developed, one box at a time, a correlation between the film holders and the exposure records is lost or difficult to retrieve. A precise subject and image description on the audiotape can help, but often fails when multiple exposures of the same scene were taken.
fig.1 With the use of a steel template, a binary notching system can be cut into the bottom lip of the film holder. This correlates the sheet film with the holder after development.
fig.4 The template in cutting position. The numbering is reversed, because the films emulsion is pointing up while in the film holder.
I have solved this problem by notching all of my film holders with a binary pattern. It leaves a permanent mark on the negative, clearly identifying the film holder used, without any intrusion into the image area. Fig.6 shows a negative and the binary pattern left from film holder number ‘21’.
The Binary System
To understand this system, you only need to understand general numbering systems, and the binary system is actually the simplest of them all. Let’s first look at the familiar decimal system. Fig.2 shows the basics of the system with two examples. From right to left, each digit is dedicated to the base of ‘10’ with increasing exponent values, each of which can hold any number from 0-9. Therefore, we have a digit for the singles, the tens, the hundreds and so on. To display the number ‘13’ in the decimal system, the digit for tens is set to ‘1’ and the singles are set to ‘3’, summing up to the desired ‘13’. We were all brought up with the decimal system, and it is second nature to us. We assume the base of ‘10’, when communicating numbers, to the point that we forget about it altogether. The binary system is very similar to the decimal system. The only difference is that it assumes a base of ‘2’ and not ‘10’. Therefore, each digit can only hold numbers from 0-1. Consequently, we now have digits for singles, twos, fours, eights, sixteens and so on. Fig.3 shows the basics of the binary system using the same two examples as before. To display the number ‘13’ in the binary system, the digits for eights, fours and singles are set to ‘1’ and the sum will make the desired ‘13’.
The benefit to our application is that each digit of a binary number can only hold a number from 0-1, whereas in the decimal system, it can be any one of ten numerals. A simple notching system can simulate one of two conditions easily, by either having a notch at a certain location or leaving the location without a notch.
Cutting the Holders
I am only familiar with the film holders from Lisco, Riteway and Fidelity. They all have a lower lip, which is taped to the holder, to form a hinge. Fig.4 shows this lip lifted up, as it would be to insert or remove sheet film. This lip also holds the film down, when the holder is closed.
The lower part of the lip is an ideal location to place the binary notches. The lip has a groove for the dark slide to fit into, and we want to make sure that only the side in contact with the film receives the notches. This prevents the use of a file, which would cut into the upper lip as well. A file would also create unwanted dust particles, which may be hard to remove. The best way to cut the notches is with the tip of a sharp utility knife, guided by a customized steel template.
Get a small steel ruler from the hardware store and cut it to length, so it fits inside of the holder. Then, using a small triangular file, create six notches, 1/8 inch deep and 1/4 inch apart from one another. Fig.4 shows the template with a sticker to mark the binary values of each notch. The numbering sequence is reversed from the table in fig.3, because we are looking at the underside of the lip while cutting the notches and at the film emulsion side when reading them. At this point, insert the template into every holder in question and notch them one by one, being very careful not to cut yourself. A pair of heavy leather gloves will protect your fingers, and a pair of goggles will save your eyes. This template will allow you to mark up to 32 double-sided holders, but if required, an additional notch will double this amount. Getting used to the binary system can be confusing at first, but you will soon get the hang of it. It is the most efficient way to cut a minimum amount of notches. Fig.5 shows where to cut the correct notches for up to 12 double-sided film holders, and fig.6 shows how to use the steel ruler to read the notches on a sample negative.
I haven’t had to eliminate any of my film holders due to focus problems or light leaks yet, but correlating my exposure records from the field to the right negative is now a much easier task.
fig.5 This notching table shows where to cut the correct notches for up to 12 double-sided film holders.
fig.6 The notches in the film holder ‘21’ left a permanent imprint on a sample negative, here shown with the emulsion side up. The same steel ruler, used to cut the notches, can be used after film processing to identify which film holder was used during exposure. This is best done with the negative in its protective sleeve, where the sensitive emulsion side is protected against scratches.
How to Build and Use the Zone Ruler
Visualization can be learned, but it takes practice
The ability to visualize a scene, and later accurately expose and develop the negative accordingly, is one of the great benefits of the Zone System. Being able to direct any subject brightness to a desired print zone on the final print gives great confidence and enables the photographer to combine creativity with predictable technical excellence. However, visualization of the final print zone densities takes practice. Many disappointing prints are the result of underestimating how dark Zone VII really is, or realizing the sobering fact that Zone III does not always reveal as much detail as anticipated.
I often ask students of my Zone System classes to identify their preferred print zones for the shadows and highlights of a sample scene. The typical answers for any particular subject area are spread relatively widely over two zones. This is not necessarily a problem, as long as it is due to individual artistic interpretation of the scene. However, the students are in much closer agreement when asked to point out the intended print density on an unmarked step tablet. This indicates that accurate visualization of print densities requires some experience, and a sample step tablet, as in fig.1, can be a valuable training aid.
How to Make Your Own
With the help of a few paper tests, a densitometer and the density table in ‘Tone Reproduction Cycle’, you could make an extremely accurate Zone Ruler. However, this level of precision is hardly necessary for a tool intended to aid in the subjective evaluation of subject brightness. Let’s look at a much faster approach, which allows you to make your own Zone Ruler with ease and appropriate accuracy.
In the darkroom and armed with a Kodak Gray Card, find the exposure time required to create a density closely matching the card’s ‘average’ gray, using a paper contrast of grade-2. Using fig.2, you can refer to this density as being Zone V and its base exposure time as being 100%. If you are working with variable-contrast papers, and are not certain how to filter for an ISO grade 2, just skip the filtration and use only the ‘white light’, because the exposure variations in fig.2 are very sensitive to paper contrast.
fig.1 The Zone Ruler provides a handy reference to the representation of subject brightness in the final print.
Now, use an 8x10-inch piece of paper and divide it evenly into ten patches. Leave the first patch (Zone IX) paper white without any exposure. Then, expose each remaining patch for a percentage of Zone V, as indicated in fig.2, by sliding a dodging card step by step from left to right after each exposure. Use the incremental percentages from fig.2 to calculate your actual exposure times from the base exposure time for Zone V. That is, cover the first patch (Zone IX) to keep it paper white, and expose for 25% of the base exposure time to create a patch matching Zone VIII. Then, move the dodging card, and expose for an additional 15% of the base time to create Zone VII, then 20% more for Zone VI and so on. This creates print densities with adequate accuracy. However, verify by checking Zone VIII, which should be just off-white. If necessary, modify to the exposure times (±5%), in order to fine-tune the Zone Ruler to your paper.
Develop and process the print normally and label the zones as shown in fig.1. Cut the print to size and glue it to a piece of mounting board, which gives your Zone Ruler more stiffness and increases its durability. My ruler has found a permanent place in the camera bag. I do not recommend any surface protection for the ruler. It just adds the risk of potential flare and alters the surface appearance to a point where it may not be representative of the final print surface anymore.
How to Use It
The Zone Ruler is used as a comparative scale. Hold it up at arm’s length, as shown in fig.3, to compare the brightness of any portion of the scene with the steps on the ruler. This enables you to distribute the entire subject brightness range over the available print zone densities.
Here are a few tips on how to use the ruler successfully and how to avoid a few pitfalls. Always try to hold the ruler so the light falls on the ruler the same way it falls on the subject area in question. In fig.3, the sun has just lost the right garage door to the shade, and the ruler is held in a very similar position. Finally, avoid light reflections on the ruler, because they may get in the way of a realistic comparison.
Don’t allow the Zone Ruler to interfere with your creative visualization process. It is a useful tool, however, to make you aware of the available print zone densities. Use it wherever an accurate and lifelike tonal interpretation is required. Nevertheless, a realistic representation of the subject tonality is not always in the best interest of creative fine-art photography. You, the artist, are still in charge of the image. You decide which subject tones are to be represented as shadow or highlight zones and give the image the appropriate impact. Use the ruler as recommended, but don’t let it stifle your creativity.
The Zone Ruler is a quick reference guide to the available print zones. It is a valuable tool to have, and easy to make. Students of the Zone System, who use the ruler, can accurately translate subject tones to realistic print zones with much more consistency than without it. Remember, however, that artful visualization is successfully performed only by the human mind.
fig.2 The individual zone patch exposure times are in %, relative to the appropriate time required to create a Zone-V density (100%). This table provides absolute and incremental exposure times.
fig.3 The Zone Ruler is held at arm’s length to compare the subject area in question with the print zone densities. Care must be taken that ruler and subject area are illuminated similarly, and that no reflection interferes with the evaluation. This is a handy support tool in the visualization process and has found a permanent place in the author’s camera bag. However, artful visualization is successfully performed only by the human mind. Do not let the ruler stifle your creativity. You, the artist, are still in charge of the image.
How to Build and Use a Zone Dial
Additional functionality for popular spotmeters
The lightmeter became part of the photographer’s toolbox about 100 years after the invention of photography. Beforehand, photographers relied on empirical methods or a set of reference tables to determine the correct film exposure. Early exposure meters consisted of a holder for light sensitive paper and comparison step wedges with increasing densities. The paper was exposed for a given time to the same lighting conditions as the scene and then compared to the step wedge. The step, which was the closest to the exposed paper in density, gave an indication of the required exposure. Lightmeters have come a long way since then and have evolved to be accurate and dependable tools no photographer wants to be without. A serious Zone System practitioner has little or no alternative than to use a spotmeter capable of reading subject luminance within an angle of 1°. This narrow angle of acceptance permits convenient tonal placement of small but important subject detail. It may not be a coincidence that the invention of the Zone System followed the introduction of the first spotmeter in 1945.
fig.1 The customized zone dial for the Pentax Digital Spotmeter is a visual reference and will simplify zone placement. Zone III and VII are marked to place shadow and highlight details.
Reading the Lightmeter in Zones
Lightmeters, including spotmeters, are calibrated to suggest a film exposure, which will render the subject detail measured as an average or middle gray in the print. We refer to this as a Zone-V exposure. Consequently, if a luminance reading is taken with the meter, and this reading is used to determine film exposure without alteration, then we have placed the subject detail on Zone V. However, if we want the same detail on Zone IV, then we give 1 stop less exposure or 2 stops less to place it on Zone III. Alternatively, a 1-stop exposure increase will place the reading on Zone VI and so on. This technique is called zone placement and can be simplified with the aid of a custom zone dial.
Fig.1 shows a custom zone dial for the Pentax Digital Spotmeter. Feel free to copy it from the book for your personal use. Once applied to the meter as shown, a light reading can be placed on any zone, providing accurate tonal value placement without calculations.
The Standard Zone Dial
It is very helpful for the student and the teacher to have a variety of educational props at hand when discussing photography in general and the Zone System in particular. Over the last few years, I have prepared many of these tools myself and most have proven to be very useful aids in my own classes, but the standard zone dial is by far the most popular. This is at least partially due to the fact that the pocket size version shown here can be used as a zone calculator and reference guide, while practicing the Zone System outside of the classroom. In addition, the use of the EV scale has reduced the complexity of similar devices to just two dials, which makes it easier to assemble and use.
All you need to build your own is a few pieces of cardboard, the use of a copy machine, some self-adhesive labels or glue, a small utility knife and some hardware to hold it together. Feel free to copy the illustrations in fig.2 from the book for personal use and glue them to the cardboard. At this point, carefully cut out the shapes, laminate with clear foil to give it some protection and use a bolt, nut and washer combination to assemble the two dials through the marked center points.
The assembled zone dial (fig.3) works well with any lightmeter that provides film sensitivity adjusted EV readings. Most spotmeters do, one exception being the Pentax Digital Spotmeter, which needs an alternative zone dial as shown in fig.1. Take a shadow reading and place its EV number next to the desired negative zone. Now, take a highlight reading and its EV number location on the dial will reveal the negative zone onto which these highlights will fall at normal development. Taking additional readings, you can estimate zone placement for various subject areas.
Necessary development corrections can be predicted from the differences between highlight zone readings and their preferred values. If, for example, the shadow zone is read and placed, and the desired highlight for Zone VIII happens to actually fall onto Zone X, then an N-2 development is required.
The final decision on exposure can be made from any aperture/time combination in the window, because the EV numbers were provided as film sensitivity corrected values from the lightmeter. In addition, the standard zone dial provides a valuable overview of zone placement for the entire scene.
fig.2 Only two disks are required to make the standard zone dial. Zone III and VII are marked to place shadow and highlight details, and in addition, the tonality extremes are shown as black and white points at Zone I·5 and VIII·5.
fig.3 The assembled standard zone dial provides a handy reference to the way subject brightness will be represented in the final print.
Make Your Own Shutter Tester
Use your personal computer and this simple circuit to test your shutter
fig.1 The circuit for the self-made shutter tester contains only simple electronic components. Either a photo diode or a phototransistor can be used as a light sensor. A capacitor is included to protect highly sensitive microphone input circuitry. If the shutter tester is used with a less sensitive line-in socket, the capacitor may be bypassed to give a stronger signal.
At the time of this writing, we cannot find an affordable shutter-speed tester available on the market. After investigating a number of alternatives, however, we can report on an elegant and simple solution to make your own.
Before diving in, it is worth noting that this method relies upon the shutter working regardless whether the camera body is open or closed. Obviously, this excludes all digital cameras and some modern film cameras, which restrict shutter operation while the film back is open or removed. All other roll-film cameras and large-format lenses can have their shutters measured with this useful self-made device.
The concept is deceptively simple. A light-detecting sensor is placed behind the camera body or lens, facing a light source placed in front of it. A convenient source of light is a battery-powered torch or an ordinary desk lamp. The circuit in fig.1 produces a small voltage pulse when the light, falling on the sensor, changes abruptly. This voltage pulse is recorded through the microphone or line-in socket of a personal computer with the aid of an audio-capture program. The program must be able to record a high-frequency signal and display the ‘audio’ waveform on a timeline. Most PC sound cards are supplied with such software, and an internet search finds several freeware or shareware audio-capture programs.
Light Sensor
The circuit in fig.1 relies on a reverse biased photo diode or transistor as a light sensor, which change their resistance corresponding to a change in incident light. Compared to traditional light-dependent resistors, photo diodes and transistors react virtually instantaneously. The voltage at the junction of the sensor and resistor changes with light level, and the change is transmitted via the capacitor to the microphone input. The capacitor blocks any DC voltages and lets just the transients pass. A positive pulse occurs when the light level increases and a negative pulse when the light is reduced. The component values are not overly critical and are easily obtained from a hobby electronics store. To make the assembly more robust, it is mounted in a small plastic box, preferably black, with the sensor mounted behind a small hole (fig.2).
fig.2 The self-made shutter tester is connected to the microphone or line-in socket of a personal computer.
Setup
Conducting the test with a camera body, the self-made shutter tester is carefully positioned, facing the film rails but without touching the delicate shutter blades. A few rubber bands or some tape will safely hold the tester in place. Depending on whether one is checking a leaf or a focal-plane shutter, the lens is attached, and set to a working aperture, or removed from the camera body altogether. The light source is placed in front of the camera, facing lens or lens opening (fig.3). The camera or lens shutter is wound, and the 3.5mm jack of the shutter tester is connected to the microphone or line-in socket of the computer.
Run the capture software and start a new ‘recording’. Immediately press the shutter and stop the recording after the shutter closes. Several seconds of recording will have occurred, so you must use the editing tools in the software to find and extract the two pulses. Now, expand the timeline to see them clearly and use the selection cursors to measure the time between the pulses, halfway up the positive pulse and halfway down the negative pulse, as shown in fig.4.
A little experimentation may follow where it could be necessary to alter the ‘microphone’ gain or the light intensity to get the signal within the range of the audio hardware. If there is no signal, it may be that the photo diode or transistor is connected the wrong way around. Note that the line-in socket of a sound card is less sensitive than the microphone socket, and therefore, it may require a stronger illumination of the light sensor. To protect your computer hardware, always start with a low setting and slowly increase illumination, as required, to get a stronger signal.
For the example shown in fig.4, the freeware audio-capture program ‘Audacity’ was used on an Apple Macintosh. The screen shots show the different waveforms recorded by a microphone and a line-in socket for a 1/500-second shutter setting. In this test, the audio sample frequency was 44.1 kHz, and 78 samples were captured between the leading edge of the two pulses. This equates to an effective shutter speed of 78/44,100 or 1/565 second, which causes a slight underexposure but is still a good result for a mechanical shutter.
fig.3 Depending on the type of shutter to be tested, the shutter tester is positioned behind camera or lens, and a light source is placed in front of the camera.
Make a separate recording for each shutter setting, calculate all effective shutter speeds and record them in a list. Optionally, also calculate the shutter-speed deviations and chart the resulting f/stop errors for the entire range (fig.5). As underexposure is more harmful to negative film than overexposure, slow shutters are better than fast shutters. This explains why the recommended acceptance criteria are more stringent towards fast shutter speeds. For all calculations, remember that the shutter speed markings on a camera or lens are rounded approximations. The true sequence is 1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256, 1/512 and 1/1024 of a second.
fig.4 Audio-capture software is used to measure the number of samples between two light pulses, which, in turn, equates to the effective shutter speed.
fig.5 Shutter-speed deviations can be charted as f/stop errors. As underexposure (fast shutter) is more harmful to negative film than overexposure (slow shutter), the acceptance criteria are more stringent towards fast shutter speeds.
Make Your Own Test Strip Printer
A useful tool for localized and continuous test strips
The creation of a high quality print is far easier with the help of an informative test strip. A few minutes of time can give the darkroom practitioner test results, revealing the right exposure and paper grade for a particular image. Additional test strips, made at potential problem areas of the image, can give us useful information to improve the print with dodging and burning techniques. An organized approach to test strips can replace an inefficient trial and error method, ultimately saving time and paper and yielding more information than any electronic analyzer.
There are two schools of thought when it comes to test strips. First, there is the localized test strip, concentrating on only one particular area of the print. This is typically a delicate highlight area, concerned with the lighter tonal values of the image. Second, there is the continuous test strip, concentrating on the entire area of the print. The choice of which type of test strip to use depends entirely on the image.
It is simple enough to create a continuous test strip. A small piece of photographic paper is placed under the enlarger and a base exposure is applied. Then, the paper is partially covered by an opaque card and an additional exposure is made. This process is repeated until five to seven different exposures are made. Creating a localized test strip is a bit more involved. In this case, the paper has to be moved precisely each time, since the exposure must be made from the same area of the image. This cannot be done accurately unless some kind of paper guide is used. Several versions of such a guide are available commercially, but to my knowledge none of them can be used to create both localized and continuous test strips.
Therefore, I decided to design and make my own test strip printer. It has since become a standard tool in my darkroom, and is used to determine exposure and contrast for every new print. This test strip printer makes use of regular 5x7-inch pieces of paper. I have a box of this size for every paper type I use on a regular basis. For rarely used and special papers, it is often easier and more economical to cut a few pieces from the existing stock. I’d like to explain first how to use the test strip printer with the help of two example images. The instructions on how to build your own test strip printer will follow at the end of this chapter.
fig.1 The important tonal values of the highlights are limited to one area of the print. This is a typical image to demonstrate the need for a localized test strip.
Localized Test Strips
The first image is shown in fig.1 and was taken in an abandoned farmhouse in Howell, Michigan USA. The model and I climbed to the attic of the farmhouse using a wooden ladder of rather questionable structural integrity. This ruled out the use of any professional lighting equipment, but I was pleasantly surprised by the amount of natural light coming through several cracks in the roof. The Hasselblad 501C, fitted with the Carl Zeiss Planar 2.8/80, was supported by a tripod to allow for an exposure time of 1 second at f/8 on TMax-400 film. The model was placed in one of the corners of the attic. In this position, all lines generated by the surrounding beams and panels lead the eye towards the model. The white dress and the blond hair are the focus point of the image.
A continuous test strip across the entire image would not be much help in this example, where the highlights are primarily located in one area of the print. Therefore, we’ll make a localized test strip to establish a basic print exposure, which holds these sensitive tonal values close to paper white, without losing their delicate highlight detail.
fig.2a-e A localized test strip is the best choice if the governing highlights are concentrated in a relatively small area of the image.
First, the negative is placed into the enlarger and the desired magnification determined. Then, the narrow window of the test strip printer is placed into position, catching the area of interest. A 5x7-inch piece of white scrap paper can be used to help with this task. Initially, your best guess at exposure time, f/stop and contrast will do. Try to err on the low side of the contrast. It is better to slowly increase the contrast, rather than having to reduce it. It will put you in control to give up shadow detail, after you have seen it.
At this point, it is time to turn on the safelights and to make the first exposure. Push a piece of 5x7-inch paper into the bottom right-hand corner of the test strip printer (see fig.2a), close it (see fig.2b), and expose the first test strip. Open the test printer and move the paper to the left by one notch (see fig.2c). The large triangle cutouts make this a simple task even when in the dark. I place a finger in the notch and move the paper until it touches the finger from the left. The second exposure time should differ from the first by 1/3 stop for rough estimates, 1/6 stop for normal test strips and a 1/12 stop for fine-tuning the image. Use increments of 25, 10 or 5%, respectively, if you would rather work in percentages. Continue with these increments until all seven exposures have been made (see fig.2d). The final test strip is shown in fig.2e after processing was completed. It shows how the test strip printer produced increasingly darker exposures for the same area of the image. It is not difficult to determine a final exposure time for the highlights from this test strip. Proper shadow detail is the next priority and is controlled with the appropriate paper contrast. This can be tested in a similar way, but see ‘Fine-Tuning Print Exposure and Contrast’ for an alternative approach. You can also prepare localized test strips for problem areas to determine corrective dodging and burning times, while achieving final tonal control and slowly creating a printing map for your image.
fig.3 The tonal values of the significant highlights are spread across the bottom of the print. This is a typical image to demonstrate the need for a continuous test strip.
Continuous Test Strips
The second image is shown in fig.3 and it was taken in a rape field close to my home in Essex, England. I drive by this field twice a day, on my way to and from work, and I had watched the progress of the vegetation. When the field finally had the distinctive yellow color, all I needed was a stormy cloud pattern to give the image the right atmosphere and bright sunshine to light up the field in the foreground. I had to wait for a weekend in May of 1999 for the conditions to be just right. The Toyo 4x5 metal field camera and the Nikkor-W 5.6/210, fitted with the Orange filter, were supported by my heaviest tripod to give solid support for an exposure time of 1/15 second at f/32 on TMax-400 film. The session still required more than two hours of patience for just the right light and cloud pattern. This type of picture is usually taken in color, but I visualized the field to be almost white, with a prominent white cloud contrasting the otherwise dark sky.
Again, we are best off to begin by establishing a basic print exposure, which holds these sensitive tonal values close to paper white, without losing their delicate highlight detail. The proper shadow detail will be established later with the proper paper grade. The prominent highlights are spread evenly across the entire image foreground with almost identical tonal value from left to right. A localized test strip would work well, but would take more time to prepare. Therefore, we’ll make a continuous test strip this time.
As done before, push a piece of 5x7-inch paper into the bottom right-hand corner of the test printer (see fig.4a), but this time leave the cover open. Expose the entire test paper for your anticipated minimum exposure time. Then, use the black pedal and cover the left strip, again with the aid of the large notches (fig.4b). Expose for an incremental 1/3, 1/6 or 1/12 stop, depending on how fine you want the increments to be, or use additional increments of 25, 10 or 5%, respectively, if you prefer. Continue with these increments (fig.4c) until all seven exposures have been made (fig.4d). The final test strip is shown in fig.4e after processing was completed. It shows how the test strip printer produced continuously darker exposures across the image. It is easy enough to determine a final exposure time for the highlight from this test strip. I also use this method to test for appropriate edge-burning.
How to Make Your Own
To my knowledge, such a versatile test strip printer is not commercially available. Therefore, I decided to make my own. Fig.5 shows an exploded view of all parts, the bill of materials and the basic dimensions. I used 1/4-inch opaque plastic sheets in black and white as the base material. The colors were chosen so that the photographic paper is only in contact with black material. However, all other visible surfaces are kept white to provide the highest possible contrast, which will aid handling in the darkroom.
The tools required for this project include a table-saw, a handsaw, a drill, a screwdriver, some adhesive, a file and some clamps. If you don’t feel confident operating these tools, I suggest you make the test strip printer from thick cardboard. The tools required are then reduced to a sharp trimming knife and some glue. You could also replace the hinges with durable tape.
fig.4a-e A continuous test strip is the best choice, if the governing highlights are spread over a relatively large area of the image.
Cut the pieces to the dimensions shown in fig.5 and smooth the edges with sand paper. The saw-tooth pattern of the white scale (2) takes a little patience, but its accuracy is important. Glue or screw the white scale to the black base plate (1), while aligning the front and right edge. Using screws rather than glue has the benefit that a flush fit between the two pieces is realized. This will keep the paper from potentially being caught in a glue gap. Now, glue the white upper cover (5) to the black lower cover (3) while aligning the back edge and both sides. Next, glue the black cover handle (6) to a convenient center location on top of the upper cover. Similarly, glue the white pedal handle (13) to the black pedal (12) centered in both directions.
Clamp the white hinge plate (4) to the base plate while aligning the back edge, and drill two 6.5-mm holes. You can distribute the hole pattern as you wish, or as I did, 1/3 from the sides. These holes will be used to hold the hinge plate in place with screws (8), washers (10) and the wing nuts (9). Place the cover assembly on the base plate and push it against the scale at the front and right hand edge. Attach the hinges (11) with small screws or glue. As a final touch, place a few self-adhesive feet (7) to the bottom of the base plate.
fig.5 The exploded view and the basic dimensions of the test strip printer
Your test strip printer is now ready for your first print (fig.6), and I hope that you find yours as useful as I find mine. It is put to good use for all my printing now.
fig.6a-b The final test strip printer assembly. Five rubber feet ensure that it stays in place during operation and test exposures.
Make Your Own Burning Card
A useful tool for fine print control
Dodging and burning are creative printing controls, which are often necessary to emphasize certain areas of the image. A ‘straight’ print might show some areas too light, while others are too dark. Adjusting the overall contrast, in an attempt to capture both ends of the print scale, may give a ‘weak’ print. For a more expressive image, optimize the local contrast in areas of interest and tweak the shadows and highlights with dodging and burning techniques to their individual optimum.
Many experienced printers simply use their own hands to cover or direct the light path to certain areas of the image. Others prefer the use of purchased or self-made templates to achieve similar results. To dodge, I use a piece of cardboard, which is mounted to a thin piece of wire. Its shape is sometimes image dependent but, most often, it is just a small circle or rectangle. My burning tool is a self-made template, which is flexible enough to help me with almost all of my images. It only takes about an hour to make it, and I will explain later how it is done. But first, I’d like to show you a sample image where the self-made burning card came in handy (fig.1).
Silver Maple Leaf
This image was taken in my backyard in Farmington Hills, Michigan USA in July of 1997, at the end of a rainy day. The reverse side of a silver maple leaf is very bright and makes a strong contrast to the dark surrounding leaves. I fixed the Hasselblad 501C to my shortest Manfrotto tripod, which I originally bought because it fits well into my suitcase. In this case, however, it was ideal, because it allowed me to get close to the ground and this scene. The Carl Zeiss Planar 2.8/80 was mounted to the camera and the close-up filter permitted a focal distance of about 60 cm. The camera back was loaded with Kodak’s TMax-100 film, which I down-rate to EI 64 for normal development.
fig.1 Adjusting overall contrast with the aim of a ‘straight’ print is not always advisable. The expressive image often benefits from final printing controls like dodging and burning.
I wanted detail in most of the dark background leaves and placed them on Zone III. The brightest parts of the leaf fell, consequently, onto Zone IX. However, I was hesitant to give N-1 development, because I was concerned about losing local contrast. I waited for the light breeze to hold for a moment and exposed at f/16 for 1 second. The negative turned out just as I expected with most of the bright leaf being well into Zone IX. Again, I hesitated to lower the paper contrast to protect the local contrast. I settled for grade 2.5, accepting that the leaf would be too light on the work print. Most of the shadows were as I wanted them, but there was too much detail in some areas, which distracted from the leaf. These areas were burned down with 2/3 stop additional exposure. Then, I raised the contrast to grade 4 and added a burn-in exposure to the leaf until it had the right level of highlight detail. The increased paper contrast allowed the fine details of the leaf to appear, without turning the rest of the leaf into an unnatural dirty gray.
fig.2 The burning card has three layers, which are held together by a screw, a washer, and a wing nut. A red cardboard was chosen as the base material. It is light enough to see the projected image, but all reflected light is of a harmless wavelength for the photographic paper.
fig.3 The underside of the burning card is painted flat black to prevent any light from reflecting back to the paper. The bottom card has two holes, one for the center pivot and another for hard to reach areas in the corner of the image.
fig.4 The circular card in the center has several hole patterns to adjust the light path to specific applications. This light path can be further modified with the top card, by covering the chosen hole pattern partially. This way, many customized shapes are possible.
How It Works
Fig.2 shows the burning card, which consists of three cardboard layers, held together by a screw, a washer, and a wing nut. This makes it easy to unlock the cards, select the hole pattern of choice and then lock the cards together again to maintain a stable selection during the burning process. A cardboard stock, red on top and white underneath, was chosen as the base material. The red side reflects enough light to see the projected image clearly, but all reflected light is reduced to a wavelength harmless to the photographic paper.
Fig.3 shows the underside of the burning card and how it is painted flat black to prevent any light from reflecting back to the paper. The bottom card has two holes, one for the center pivot and another for hard-to-reach areas in the corner of the image. Using the outside hole for corner-burns maintains light protection for the rest of the image.
Fig.4 shows the center card and one of its several hole patterns, which are used to adjust the light path to specific applications. This light path can be further modified with the top card, by partially covering the chosen hole pattern. A half-moon shape is easily created by covering half of the circular hole, or a triangle is created by covering the square diagonally. This way, it is possible to produce countless customized shapes.
How to Make Your Own
Any art store sells sturdy poster board, such as I used for the burning card, in many sizes and colors. If you are lucky, you’ll find the two-tone variety. The optimum card would be medium red on one side and flat black on the other. Otherwise, select the red board and spray-paint one side flat black, before you start cutting it. They are usually sold in DIN-A1 (2x3 feet) and that will be more than enough to make an DIN-A3 (11x17 inches) card and leave you with enough material to make a variety of small dodging tools. You can use the exploded view in fig.5 and the bill of materials as a rough guide for dimensions, but it is probably best if you customize the sizes and the hole patterns to meet your own needs.
fig.5 The exploded view and the basic dimensions of the burning card
Cut a cross-shape, rather than drilling a hole, where you want the screw to penetrate the cardboard. The extra material will help the screw to cut its own thread and make a more reliable fit. Use a large ‘automotive’ washer, because it will distribute the clamp force over a larger area and reduce wear. Make sure that all holes are on a centered path around the screw, because the holes in the bottom card need to be able to reveal every hole pattern completely. You can do so using a drafting compass to mark a large circle with the fixing hole as its center. Now, place the center of every hole pattern, in even increments, along the perimeter of that circle. I’m sure you will enjoy having this tool.
fig.6a-b The burning card is being disassembled. Only one screw holds the three cards in place and provides the pivot point for the hole pattern.
Exposure, Development and Printing Records
A small investment in time with high returns
There is no doubt about it. Film exposure, development and printing records are invaluable. The ability to recall scene metering, filtration, exposure and development, or the final print manipulation in the darkroom will certainly minimize the time required to fine-tune one’s technique. It is also the only way to find out why things did not turn out as expected or to reliably repeat the things which did. Depending purely on memory is a guarantee for failure.
Unfortunately, taking notes during the photographic process is rather boring, often cumbersome, potentially disruptive to the creative process, possibly time consuming, and is, therefore, generally considered to be a burden to most photographers. It seems reasonable after an hour or two in the darkroom to spend a few moments to scribble down how a print was dodged and burned, but pulling out pencil and pad in the field every time an exposure is committed to film seems like too much administration to most of us. However, the benefits of committing memory to paper clearly outweigh the labor involved, especially if the labor can be minimized through a bit of planning and the use of some templates, which eliminate repetitive tasks. I don’t particularly like taking records either, but I have nonetheless recorded film exposure and development data for most, and printing records for all, my negatives. In my opinion, it is a high return on a small investment of time. A copy of my standard record-keeping form is supplied in the ‘Tables and Templates’ chapter, and fig.1 shows a filled-out sample. It is a modified version of an Ansel Adams proposal and has the benefit of keeping film and print records together on one sheet. I propose to file it with the negatives and proof sheets, having it at hand for later use.
fig.1 This is a standard form to keep exposure, development and printing records together on one sheet. A blank record sheet is supplied in the ‘Tables and Templates’ chapter. Feel free to copy it from there for your personal use, but please take care not to damage the book.
(based on an original by Ansel Adams)
Exposure Records
The left-hand side of the form is used to record all relevant data about the film’s exposure. On the top, the camera body and lens used for this exposure are entered. The filter section allows for marking the use of major contrast filters according to their Wratten numbers, neutral and graduated density filters, as well as some special filters. There is also room to record the negative number for roll film or the number of the negative holder, if sheet film is used.
The rectangle provides space to record light readings taken with a spotmeter. A simple line drawing of the scene suffices to record where shadow and highlight readings were taken. Once the negative is developed, a density reading will verify if film exposure and development are under control, or if they need modification. The Zone System bar is used to record the exposure value (EV) readings for significant shadow and highlight zones and to calculate the appropriate film development.
The film development and the target developer control the exposure index (EI) best suited for the film/developer combination used. This information is taken from a previously conducted film/developer test. See ‘Customizing Film Speed and Development’ for details. Several aperture/shutter combinations will fulfill the exposure requirement set by EI and EV. Select one from your lightmeter dial or consult your self-made ‘Zone Dial’, and enter the combination under ‘Basic Exposure’. Any exposure adjustments due to filter factors, bellows extensions or film reciprocity are filled in and totaled. I usually record them in stops, making it simpler to adjust the ‘Basic Exposure’ to the ‘Final Exposure’. Three icons allow recording of the lighting situation in form of daylight, flash or artificial light, respectively.
Recording all these steps in the field or on assignment is a time-consuming task, so I use a handheld voice recorder to quickly gather the information. After the scene is metered and the exposure is set on the camera, I just record all the data onto the tape. Looking at a sample of the form while recording avoids omitting any settings. At the end of the day, the tape is rewound and the data is transferred to the form without any need to rush. This is the least time-consuming operating procedure I have found, and it is an acceptable task considering the benefit of having all exposure data for future reference.
Development and Printing Records
The right-hand side of the form is used to record all relevant data about film development and printing. Most of it is self-explanatory and requires little actual writing due to the multiple-choice layout. After film processing, all typical parameters are recorded under ‘Film Development’ and significant highlight and shadow densities are measured, if a densitometer is available. Enter the densities and calculate the difference between the two. This is the relative log exposure range of the negative and, consequently, the required paper contrast to print highlights and shadows equally well. If a densitometer is not available, rely on a darkroom meter or your experience for the initial paper contrast setting.
fig.2 The 15-digit image numbering system can keep thousands of negatives and digital image files organized. It is easy to locate the negative or digital file for a particular print, as long as the print is labeled with the corresponding image number.
Under ‘Print Development’, all parameters required to reproduce an identical print are entered. The multiple-choice section takes care of enlarger settings, including head tilt and lens shift/tilt for enlargers capable of ‘Scheimpflug’ adjustments. Enter the exposure time for the significant print highlights under ‘Base Time’, and record all print manipulations in stops, based on this time, in the printing map.
Image Numbering System
In addition to maintaining clear printing records, it is equally important to have a consistent numbering system for our images. The 15-digit image numbering system in fig.2 keeps negatives and digital image files organized. I have used it to catalog my moderate library, which contains thousands of images and spans several decades. It has served me well, and there is never an issue in locating the negative or digital file for a particular print, as long as the print is labeled with the corresponding image number.
The image number starts with 8 digits to identify the year, month and day on which the image was taken. This is followed by a single letter for the method of image capture: ‘a’ for analog and ‘d’ for digital files. For analog files, the next 4 digits are used to identify the roll of film shot that day, and the specific negative frame on that roll. If I shot sheet film, the first 2 digits are used to point out the format (‘45’ for 4x5 sheet film) and the other two identify the film holder. For digital files, all 4 digits simply reflect the exposure counter of the digital camera, and I add 2 digits to distinguish different versions of image manipulation.
I hope that these examples of record keeping will help you maintain your own data and image files. Use the forms provided as is or customize them to your liking. Spending the extra effort will pay off big returns in the long run, and it will allow you to learn from your own experiences more quickly. It is satisfying to pick up a negative and start printing where you left off several months or years ago whenever you want to. However, do not use these records too rigidly. In order to improve, you have to deviate from previous exposures or print manipulations. Nevertheless, modifying previous settings, rather than starting from scratch, carries more educational value.
Making Prints from Paper Negatives
An old technique revisited with new materials
We expose and develop film solely to produce an intermediate film negative, which we subsequently contact print or enlarge to produce the final paper positive. This so-called negative/positive process was not how photography started, and when finally invented, early negatives were made from paper and not from film. Revisiting this old technique with modern materials creates very usable images of surprising quality.
The first successful photographs were produced in France during the 1820s by Joseph Nicephore Niépce, after he experimented for almost 30 years to create permanent images. By 1824, he had settled on a process for which a pewter plate is coated with a mixture of bitumen and lavender oil, a solution that hardens on lengthy exposure to light. The plate is placed inside a camera obscura and exposed for hours to capture the image. It is then removed, and any still soluble solution remaining in less exposed areas is washed out with pure lavender oil. Niépce called his process heliography, which literally means ‘sun writing’. The oldest surviving photographs are heliographs made by Niépce in 1825 and 1826.
fig.1 Following in the footsteps of the inventors of photography, we can make B&W prints without film but from paper negatives, and, using modern resin-coated papers, these negatives are of surprisingly high quality.
In 1829, Niépce agreed to form a business and development partnership with Louis J. M. Daguerre, but Niépce died only four years later. Daguerre, a painter and businessman without formal technical education, was forced to continue the experiments alone. By 1837, he had developed the fundamentals of a new and far more sophisticated method of creating permanent photographic images. The process involved coating a polished copper plate with light-sensitive silver iodine, and, subsequent to its exposure, developing it over poisonous mercury vapors. The resulting image was made stable by immersing the plate into a strong salt solution, followed by a wash. Daguerre’s process produced a detailed one-of-a-kind picture of high quality, which he called Daguerreotype. He announced his results to the French Academy of Sciences on January 7th, 1839. After several failed attempts to market his invention, he managed to sell the patent rights to the French government in exchange for a life-long pension for himself and Niépce’s widow. On August 19th, 1839, the French government declared the invention of photography a gift ‘free to the world’.
For decades, several other individuals also tried to combine the camera obscura and chemistry to make permanent photographs. The most notable among them was William Henry Fox Talbot in England, who made successful photographs as early as 1833. After 1835, however, he made very little progress and eventually discontinued his developments. Due to many other interests, he also failed to make his invention public at the time. It was not until he heard rumors about Daguerre’s invention that he hurriedly decided to prepare and present his paper to the Royal Society of London on January 25th, 1839, consequently missing Daguerre’s presentation by only a few days. Talbot’s invention, which he called Calotype, was not awarded a patent until 1841. His two-stage process required that a negative image be produced on light-sensitive paper first. The final positive image was then made on another sheet of light-sensitive paper by exposing it to light through the paper negative. Compared with Daguerreotypes, the quality of the early Calotypes was somewhat inferior. However, the great advantage of Talbot’s invention was that an unlimited number of almost identical positives could be made at any time. In fact, today’s photography is based on nearly the same principles, whereas the one-of-a-kind Daguerreotype turned out to be too limiting.
fig.2 This enlargement was made from the oldest camera negative in existence, taken by William Henry Fox Talbot in 1835. It shows a latticed window in the South Gallery of Lacock Abbey in Wiltshire, England and was taken from inside the abbey, which was Talbot’s family home at the time. In his notes Talbot had written:
Latticed Window (with a Camera Obscura) August 1835
When first made, the squares of glass about 200 in number could be counted, with help of a lens.
© Reproduced from the National Museum of Photography, Film, and Television by courtesy of the Science and Society Picture Library.
Modern Materials and Equipment
Talbot’s process is easily simulated with modern materials. The primary material properties for paper negatives are light sensitivity and translucency. Other requirements include good resolving power and flatness. The most-suitable modern material for paper negatives is resin-coated (RC) paper. They have an acceptable light sensitivity and are translucent enough for contact printing. Their resolving power is beyond human detection, and they stay reasonably flat inside the camera. Resin-coated papers, free of manufacturer logos, as in Ilford Multigrade IV-RC, can be used to prepare paper negatives of surprisingly high quality.
Any camera format will work, but since we are limited to contact printing, it is best to use the largest negative format possible. Large-format cameras are especially ideal. An old 11x14 or 8x10 view camera can be restored to make perfect paper negatives for contact printing. Also consider the use of large or medium-format pinhole cameras to create images of unique softness and beauty. Large-format benefits aside, don’t let the exclusive availability of a 35mm camera stop you from walking in Talbot’s footsteps. After all, the oldest paper negative in existence measures only about 1 inch square in size (fig.2). Revisiting this old technique is not just an interesting experiment in rediscovering the fundamentals of analog photography. It also returns surprisingly clear images of good tonality if used with modern materials and equipment.
Exposing the Paper Negative
To ensure accurate paper-negative exposures in the camera, it is important to determine the effective paper speed. As with film, it is best to perform a customized test with the actual equipment and materials used. Doing so with my equipment and developing technique revealed a paper speed of EI 4 for Ilford Multigrade IV-RC. I suggest you test your favorite paper around this value in 1/3 or 1/2 stop increments. Find the speed that ensures adequate shadow detail in the paper negative, ignoring midtone and highlight areas. Fig.3a shows a typical result of such an initial test. The shadows have plenty of detail, but the highlights are far too dense to make a decent print from this paper negative. The reason is that modern photographic paper is not designed for this application. It is designed to create a positive image by reversing the tonality of a relatively low-contrast negative.
A ‘normal’ scene has a subject brightness range of 6 stops from the deep shadows of Zone II to the bright highlights of Zone VIII. This is not a problem with film negatives, which can handle exposure ranges of up to 15 stops or more, but it can be a problem with paper negatives. Exposed to unfiltered light, variable-contrast (VC) paper has an exposure range of only 3 1/2 stops, and if the exposure for a normal scene was metered for the shadows, as in fig.3a, then the highlights are doomed to block up. Nevertheless, with appropriate filtration, the exposure range can be significantly extended. Green (G11) and yellow (Y8) filters, typically used to enhance the contrast with film negatives, extend the paper exposure range to about 6 stops. I recommend the use of a yellow filter, because it requires less exposure correction to achieve a similar effect. Fig.3b shows how the use of a yellow filter and an exposure increase of 1 stop kept the shadow detail, while significantly reducing the highlight densities. This is a big improvement over the unfiltered exposure in fig.3a, and is all we can do during the exposure of the negative, but the resulting negative density range is still too wide to print the paper negative on grade-2 paper.
fig.3a unfiltered exposure
Exposing photographic paper in the camera, without filtration at EI 4, gives adequate shadow detail, but the highlights are far too dense to make a decent print. The subject brightness range is clearly beyond the capability of modern darkroom papers.
fig.3b filtered exposure
Using a yellow filter (Y8), and increasing the exposure by 1 stop, maintains the shadow detail, while significantly reducing the highlight densities. However, the paper negative density range is still too wide to fit on a grade-2 paper.
fig.3c filtered exposure and weak development Exposing as in fig.3b, plus using a highly diluted paper developing solution, limits the highlight densities of the paper negative to manageable levels and secures shadow detail.
Developing the Paper Negative
In regular B&W processing, the 6-stop subject brightness range of a normal scene is reduced to a negative density range of 3 1/2 stops during the development of the film in order to match the 3 1/2-stop exposure range of grade-2 paper. The filtered paper negative in fig.3b shows detail from shadows to highlights, but uses the entire paper density range of 7 stops to do so. This is far too much contrast to make a successful positive on normal-contrast paper.
With film negatives, contrast is controlled through development time. Too high of a negative contrast is avoided by reducing the development time; a lack of contrast is compensated for by increasing the development time. Resin-coated (RC) paper, on the other hand, must be fully developed to avoid uneven development and ensure quality results. Consequently, reducing the development time is not an option to control the paper negative contrast.
However, one can reduce the developer concentration to successfully control paper negative contrast. My standard paper developer is Kodak Dektol, diluted with water to a 1+2 solution. The paper negative, shown in fig.3c, received the same filtered exposure as in fig.3b, but it was developed in a relatively weak 1+8 solution of Dektol for the entire standard duration of 90 seconds. The resulting negative has a 3 1/2-stop density range and prints well on a grade-2 paper.
Printing the Paper Negative
Producing a print positive from a low-contrast paper negative is as simple as making a typical contact print. Without a negative in the carrier, the enlarger head is raised until it can be used to illuminate the entire baseboard. At this point, the enlarger only functions as a convenient light source, making it easy to control the exposure with a timer and the required paper contrast through already tested light-filtration values.
Place the printing paper into the middle of the baseboard, put the paper negative facedown on top of it and sandwich the assembly by covering both with a heavy sheet of glass. This brings the two emulsion sides firmly into direct contact with each other and makes for optimum print quality. The light from the enlarger will travel through the glass into the paper core of the negative, where it is totally diffused before it reaches the negative emulsion. The paper core should be as uniform as possible, and the back of the paper must be free of manufacturer’s imprints. This is the case with the current Ilford Multigrade IV-RC.
Test for the optimum print exposure as you would for any other contact print, and adjust the paper contrast to utilize the entire paper negative density range. Do not hesitate to apply dodging and burning to further optimize print tones.
If you are willing to trade print quality for unusual effects, experiment with textured sheets, or simply turn the paper negative around. Using the paper thickness as a spacer, and diffusing the negative image through the paper core before it reaches the printing paper, leads to a softness that might suit certain images.
Technical Background
Although knowledge of the underlying photographic principles is necessary for a full appreciation of this technique, no such knowledge is required to implement it, make interesting prints from paper negatives or just have fun with it. Consequently, some technical background is included for the more technical-minded photographers. Others, having a preference for image making over science, may skip this section and get their cameras ready.
The ability to get any paper grade from a single sheet of paper has made variable-contrast (VC) paper the prime choice for many photographers today. VC papers are coated with a mixture of separate emulsions, all of which are sensitive to blue light but vary in sensitivity to green light. Consequently, each component has a different spectral sensitivity, providing a different contrast. Blue light provides maximum contrast, and green light keeps contrast at a minimum. However, the paper is orthochromatic, insensitive to red light, which is why safelights work as well as they do. In so many words, variable-contrast papers are ideally suited for darkroom work. This changes when we use VC papers for in-camera exposures and turn them into paper negatives.
fig.4 Typical VC paper is over-sensitive to blue light when compared to the spectral sensitivity of human vision, resulting in a harsh high-contrast negative not suitable for pictorial work. A standard green or yellow filter easily corrects for this over-sensitivity and helps to create a paper negative of less contrast with a tonality similar to that of orthochromatic films.
Fig.4 shows how typical VC paper is over-sensitive to blue light when compared to the spectral sensitivity of human vision. During an average daylight exposure, all components of the paper emulsion react strongly to the UV radiation and blue light content. The reaction to green light is limited, and there is no reaction to red light. The result is a harsh high-contrast negative, which is not suitable for pictorial work (see fig.3a).
A standard green or yellow B&W contrast filter easily corrects for this over-sensitivity, which helps to create a paper negative with less contrast and a tonality similar to that of orthochromatic films. Fig.4 also illustrates how the effect of each filter is almost identical. Nevertheless, the yellow filter has the advantage of requiring only a 1-stop exposure correction, whereas the green filter needs 2 stops more light. The orthochromatic nature of photographic paper prevents a closer match to the spectral sensitivity of human vision, and for the same reason, paper negatives made from typical darkroom papers also have a tonality difference to panchromatic film.
At first, I was surprised by the excellent print quality achieved through paper negatives. The prints are typically sharp, clear and resolve fine detail beyond detection through the unaided eye. This becomes more understandable when we remind ourselves that standard human vision resolves 7 lp/mm, and critical observation senses detail up to 20 lp/mm. Normal printing paper, on the other hand, has a resolution limit of up to 60 lp/mm. This is not as good as film or 35mm lenses, but it is almost as good as most medium-format lenses and better than some large-format lenses. Since we are using our paper negatives only for contact printing, we are sure to get almost the entire optical potential of our lenses onto the paper, and that is more than our eyes can resolve.