8. Understanding Colors and Channels

In the world of design, color is one of the most important elements. When you’re creating a brochure, advertisement, or banner using Adobe Photoshop, good use of color attracts the attention of the viewer. It also helps draw the elements of your design into one cohesive unit. Color is a strong motivator and is used in all aspects of our daily life.

Since color is so important to design, Photoshop lets you use industry-standard color sets, or you can create and save your own customized color palettes. You can also color correct a photograph by removing the color entirely or selectively remove colors from portions of the image. In addition, Photoshop gives you ways to select areas based on color, and then fill those areas with any color you choose.

Not only is it important to understand how color is used, it’s also important to understand how Photoshop manages color information and that’s where the Channels palette comes into the picture. Channels are where color information is stored. The number of channels in an image is based on its color mode, or color model, such as RGB (Red, Green, Blue) or CMYK (Cyan, Magenta, Yellow, and Black). A firm understanding of channels and color modes, and their function in Photoshop will go a long way in helping you control and manage color.

When adjusting your image, you can use various commands—Auto Contrast and Color, Curves, Color Balance, and Brightness/Contrast, Saturate and Desaturate, just to name a few. You can also use the Match and Selective Color adjustments to further fine-tune your image. Photoshop also provides a photo filters adjustment, as well as a shadow and highlight adjustment to correct those over or under-exposed images. With all of the commands and adjustments available, the real dilemma will be where do you begin?

Working with 8, 16, and 32 Bit Images

PS 1.5, 9.4

It’s all about the numbers, and that’s a fact. The number of colors available for displaying or printing each pixel in an image is called bit depth—also known as pixel depth or color depth. A higher bit depth means more available colors and more accurate color representation in an image. A bit depth setting of 2-bit displays 4 colors; 4-bit displays 16 colors; 8-bit displays 256 colors; 16-bit displays 32,768 colors; and 24-bit and 32-bit, both of which display 16.7 million colors. Normal digital images have 8-bits of data per channel. For example, an RGB image with 8-bit channels is capable of producing 16.7 million colors (a 24-bit RGB image: 8 bits × 3 channels) possible colors per pixel. While that may seem like a lot of color information, when it comes to color correction and adjustment, it isn’t.

In response to needing more control, Photoshop supports 16-bit and now 32-bit—known as High Dynamic Range (HDR)—images. High Dynamic Range works with images in 32-bits-per-channel, extended dynamic range. It’s all about dynamic range. Dynamic Range is the ability of a channel to capture information from black to white, dark and bright areas of an image. An 8-bit channel image has a dynamic range of 250:1 (per channel), similar to the dynamic range of printed paper or a computer display. A16-bit channel image has a dynamic range of 65,000:1, and a 32-bit channel image has a dynamic range of over 200,000:1. The greater dynamic range translates into better control over an image, when making fine color, and contrast adjustments using Levels and Curves (shown below). Working with HDR images is very similar to using camera RAW files and applying exposure changes after the fact. Photographers can capture the full dynamic range of a scene with multiple exposures and merge the files into a single image.

Changing Bits Per Channel

The ability of working with 32-bit images is new to this version of Photoshop, so you have a limited use of adjustments and filters. However, when you convert an image from 32-bits into 16-bits, all of your adjustments are available even though you lose some filters.

Therefore, when color or contrast adjusting an image, first convert a standard 8-bit image to 16-bits, and do all the corrections. This helps prevent loss of color information, and banding between light and dark shades. Once all the color/contrast adjustments have been made, you can (if necessary) convert the image back to 8-bit. It’s that simple. When you convert a 16-bit image to 32-bits, you need to use the Flatten Image command on the Layers menu on the image first. You can change an image’s bits by displaying the image, clicking the Image menu, pointing to Mode, and then clicking 8 Bits/Channels, 16 Bits/Channels, or 32 Bits/Channels.

When you convert a 32-bit image to 8- or 16-bits per channel, Photoshop opens the HDR Conversion dialog box to let you make exposure and contrast corrections, so the image retains the dynamic range you want. The Exposure And Gamma option lets you manually adjust brightness and contrast. Drag the Exposure slider to adjust the gain and drag the Gamma slide to adjust the contrast. The Highlight Compression option automatically adjusts highlight values to fit within the range for 8- or 16-bit images. The Equalize Histogram option automatically preserves image contrast. The Local Adaptation option adjusts the tonality (local brightness regions) in the image. Drag the Radius slider to specify the size of the local brightness regions and then drag the Threshold slider to specify the distance between tonal values before they are not included in the brightness region. If you want to reuse these settings in the future, you can save them, and then load them again as needed.

Viewing 32-Bit Images

The dynamic range of HDR images exceeds the display capabilities of standard monitors. When you view a 32-bit HDR image, the highlights and shadows may look dark or washed out. To correct the problem, Photoshop allows you to adjust 32-bit preview options, so 32-bit images display properly on your monitor. The preview options are stored in the image file, so each file retains its own settings. To set preview options, open a 32-bit HDR image, click the View menu, and then click 32-Bit Preview Options. In the 32-bit Preview Options dialog box, select the preview settings (described earlier in this topic) you want, and then click OK.

Working with the Channels Palette

The Channels palette is Photoshop’s storage locker for color and selection information. For example, when you open an RGB image, the Channels palette displays color channels of red, green, and blue. When you open a CMYK image, the color channels are cyan, magenta, yellow, and black. These primary color channels are defined as the native color channels of the image. The Channels palette can also contain spot-color channels and selection masks. In addition, to color information and selection masks, the Channels palette contains a composite channel. The composite, when selected, lets you view the full-color image in the document window. Selecting any of the individual native color channels changes the active view of the image to display the selected color channel. The Channels palette stores color information using shades of gray, and each color channel is capable of displaying 256 steps from black to white. A zero value pixel displays as black, and a 255-value pixel displays as white. The darker the shade of gray, the less of the selected ink color is used to create the visible colors within the image.

Work with the Channels Palette

Open a color document.

Select the Channels palette.

Click on the individual channels to view the native color channels of the active document.

Click the composite channel to view the full-color image.

Working with Color Modes

PS 1.3

Color modes define the colors represented in the active document. Although you can change the color mode of a document, it is best to select the correct color mode at the start of the project. Photoshop’s color modes are Bitmap, Grayscale, Duotone, Indexed Color, RGB (Red, Green, and Blue), CMYK (Cyan, Magenta, Yellow, and Black), Lab, and Multichannel. See “Selecting Color Modes and Resolution” on page 13 for information on best use for each color mode. The number of channels in an image depends on its color mode. For example, CMYK image contains at least four channels, one for each color.

Color modes determine the number of colors, the number of channels, and the file size of an image. For example, a RGB image has at least three channels (like a printing plate), one for each red, green, and blue color information. Color modes not only define the working color space of the active document, they also represent the color space of the output document. It’s the document output (print, press, or monitor), which ultimately determines the document color mode. Color modes do not just determine what colors the eye sees; they represent how the colors are mixed, and that’s very important because different output devices use different color mixes.

Therefore, when selecting a color mode, know the file format of the document, and where it will be used. An image taken with a digital camera, and then opened in Photoshop would most likely be in the RGB color mode. An image displayed on a monitor would be RGB, or possibly Indexed Color. A photograph scanned on a high-end drum scanner would most likely be in the CMYK color mode. An image being sent to a 4-color press would be CMYK too. If you were creating a Photoshop document from scratch, the color mode chosen would represent the eventual output of the document, such as a Web page, inkjet printer, or a 4-color press.

Switching Between Color Modes

Unfortunately, images do not always arrive in the correct format. For example, you take several photographs with your digital (RGB) camera, but the images are being printed on a 4-color (CMYK) press, or you want to colorize a grayscale image. Changing color modes is a snap, but changing the color mode of an image isn’t the problem. The problem is what happens to the digital color information when you change color modes. For example, if you open an RGB image with the intent of sending it out to a 4-color press (CMYK), the smartest course of action is to remain in the RGB color mode through the processing of the image, and then convert the image into the CMYK mode. The reason is in how Photoshop moves between those two color spaces. For example, if you move a color-corrected CMYK image into the RGB color mode, and then back to CMYK, the colors shift because Photoshop rounds color values during the change process. Not to mention that a CMYK image is 25% larger than an RGB image, and the RGB color mode represents the color space of your monitor, not CMYK. It is impossible to view a subtractive CMYK color on an RGB device. If, however, the image originally came to you as a color-corrected CMYK image, then stay and work in that color mode. See topics in this chapter for specific steps to switch between color modes.

Understanding the RGB Color Mode

PS 1.3

The RGB color mode is probably the most widely used of all the color modes. RGB generates color using three 8-bit channels: 1 red, 1 green, and 1 blue. Since each channel is capable of generating 256 steps of color; mathematically that translates into 16,777,216 possible colors per image pixel. The RGB color mode (sometimes referred to as Additive RGB) is the color space of computer monitors, televisions, and any electronic display. This also includes PDA’s (Personal Digital Assistants), and cellular phones. RGB is considered a device-dependent color mode. Device dependent means that the colors in images created in the RGB color mode will appear different on various devices. In the world of computer monitors and the Web, what you see is very seldom what someone else sees; however, understanding how Photoshop manages color information goes a long way to gaining consistency over color.

Convert an Image to RGB Color

Open an image.

Click the Image menu, point to Mode, and then click RGB Color.

Photoshop converts the image into the RGB color mode.

Understanding the CMYK Color Mode

PS 1.3

The CMYK color mode is the color mode of paper and press. Printing presses (sometimes referred to a 4-color press) convert an image’s colors into percentages of CMYK (cyan, magenta, yellow, black), which eventually become the color plates on the press. One at a time, the plates apply color to a sheet of paper, and when all 4 colors have been applied, the paper contains an image similar to the CMYK image created in Photoshop. The CMYK color mode successfully takes an image from a monitor to paper. Before converting an image into the CMYK mode, it’s important to understand that you will lose some color saturation during the conversion, known as out of gamut. To view the areas of an RGB image that will lose saturation values, click the View menu, and then click Gamut Warning. Photoshop will mask all the areas of the image that are out of gamut.

Convert an Image to CMYK Color

Open an image.

Click the Image menu, point to Mode, and then click CMYK Color.

Photoshop converts the image into the CMYK color mode.

Understanding the Grayscale Color Mode

PS 1.3

The grayscale color mode utilizes an 8-bit pixel (8 on/off light switches) to generate 1 black, 1 white, and 254 shades of gray. Although scanning and working on old black and white images might seem the obvious reason for using the grayscale color mode; the speed and power of Photoshop, combined with faster computer systems, has prompted most photo restorers to switch to the RGB color space because of its greater versatility, and it’s ability to generate millions of colors (or shades of gray). Yet despite the move to RGB, the grayscale color mode is still used extensively on black and white images, where file size is a consideration (grayscale images are 2/3^rds smaller than RGB), and where output to rag style papers, such as newsprint, lack the ability to produce the detailed information available with RGB.

Convert an Image to Grayscale

Open an image.

Click the Image menu, point to Mode, and then click Grayscale.

The image is automatically converted into the grayscale color mode.

Did You Know?

You can colorize a grayscale image. Convert the image into the RGB mode, and then select a color, brush, and brush size on the Options bar. The trick is to change the blending mode of the brush on the Options bar to Color. Then, as you paint on the image, the selected color will replace the original grays.

For Your Information: Colorizing a Grayscale Image

If you’re planning on colorizing a grayscale image, you can increase your control of the image by creating a layer directly above the image layer, and painting in the new layer. Leave the blending mode of the brush at Normal, and change the blending mode of the new layer to Color. When you paint, the color is applied and controlled in the new layer, and you have the additional option of using layer opacity to control the intensity of the effect.

Understanding the Bitmap Color Mode

PS 1.3

Bitmap images consist of two colors: black and white. Bitmap images are sometimes referred to as 1-bit images. Think of a bitmap as a light switch with two positions, on and off. Each pixel in a bitmap image is either on or off, black or white. Because they are only 1-bit, the file size of a bitmap image is typically very small. Bitmap image have limited use, but are employed for black and white ink drawings, line art, sketches, and for creating halftone screens.

Convert an Image to Bitmap

Open an image.

Click the Image menu, point to Mode, and then click Bitmap.

Important

Before converting an image into a bitmap, it must first be in the grayscale color mode.

Enter a value for Output Resolution.

Click the Use list arrow, and then select from the available options:

50% Threshold. Converts pixels with gray values above the middle gray level (128) to white and below to black. The result is a high-contrast, black-and-white image.
Pattern Dither. Converts an image by organizing the gray levels into geometric patterns of black and white dots.
Diffusion Dither. Converts pixels with gray values above the middle gray level (128) to white and below to black using an error-diffusion process. The result is a grainy, film like texture.
Halftone Screen. Simulates the effect of printing a grayscale image through a halftone screen.
Custom Pattern. Simulates the effect of printing a grayscale image through a custom halftone screen. This method lets you apply a screen texture, such as a wood grain, to an image.

Click OK.

Understanding the Indexed Color Mode

PS 1.3

The indexed color mode gives you two advantages. You can create images as small as grayscale (8-bit pixels), and you get color instead of shades of gray. Its small file size, and its ability to generate color make is a winning color mode for images displayed on Web pages, as well as graphics used in computer-generated presentations. Its one drawback is the number of colors generated, indexed images generate a maximum of 256 colors (the same as the steps of gray in a grayscale image). The good news is you get to choose the colors. When you convert an image into the indexed color mode, Photoshop creates a color lookup table (CLUT) to store the images color information. When a color in the image cannot be found in the lookup table, Photoshop substitutes the closest available color.

Convert an Image to Indexed Color

Open an image.

Click the Image menu, point to Mode, and then click Indexed Color.

Select from the following Indexed Color Mode options:

Palette. Click the list arrow to choose from the available color palettes, or click Custom and create your own palette.
Colors. Select the number of colors for the lookup table (9 to 256).
Forced. Force the lookup table to hold specific colors. Black And White adds a pure black and a pure white to the color table; Primaries adds red, green, blue, cyan, magenta, yellow, black, and white; Web adds the 216 web-safe colors; and Custom allows you to specify your own colors.
Transparency. Select the check box to preserve transparent areas of the image (if there are no transparent areas, this option is disabled).

Select from the following options:

Matte. Click the list arrow to fill transparent areas of the original image with a specific color.
Dither. Click the list arrow, and then select a pixel-mixing (dither) scheme. Dithering helps transitional areas of the image (shadows, light to dark) appear more natural.
Amount. If the Dither option is selected, the Amount instructs Photoshop how much color information to use in the dithering process (0 to 100).
Preserve Exact Colors. Select the check box to hold exact color measurements in the lookup table.

Click OK.

Did You Know?

You can adjust the color lookup table (CLUT) of an indexed image. Click the Image menu, and then click Color Table. Click the Table button, click Custom, and then click on one of the colors in the table. Photoshop opens a color picker dialog box, and lets you change the selected image color.

Understanding the Lab Color Mode

PS 1.3

The Lab color mode is an old color measuring system. Created in France in 1939, its purpose was to measure color based on visual perception. Since computers were not around in 1939, the Lab model is not based on a particular computer or operating system, and so Lab color is device independent. Lab measures color using a lightness channel, an “a” channel (red to green), and a “b” channel (blue to yellow). Lab works well for editing images obtained from Photo CD’s, moving images between operating systems (Photoshop Mac to Photoshop Win), and for printing color images to PostScript Level 2 or 3 devices. Because of its ability to separate the gray tones of an image into an individual channel (lightness), the Lab color mode is excellent to sharpening, or increasing the contrast of an image without changing its colors. Just convert the original RGB image to Lab color, select the Lightness channel, and perform sharpening, or Levels and curves adjustments directly to the channel.

Convert an Image to Lab Color

Open an image.

Click the Image menu, point to Mode, and then click Lab Color.

Photoshop converts the image into the Lab color mode.

Did You Know?

You can use the Lab color mode to archive RGB color images. Since the Lab space is device independent, and RGB is device dependent, archiving RGB images in the Lab color mode, stabilizes the image’s color information and insures color accuracy, no matter what editing application used.

Understanding the Duotone Color Mode

PS 1.3

The Duotone color mode, converts a grayscale image into duotone (2-color), tritone (3-color), and quadtone (4-color) image using 2 to 4 custom inks. Duotones are frequently used to increase the tonal depth of a grayscale image. For example, most printing presses produce 50 levels of gray per color. By converting an image into a duotone, and using black and a mid gray, the press can produce a grayscale image with more dynamic range. A more common method for employing the duotone color mode is to create an image with an overall colorcast. For example, converting the grays in the image to sepia tone. If you’re uncertain how to create the proper color mix for a duotone image, Photoshop comes equipped with dozens of sample duotone color values.

Convert an Image to Duotone

Open an image.

Click the Image menu, point to Mode, and then click Duotone.

Important

Before converting an image into a duotone, it must first be in the grayscale color mode.

Click the Type list arrow, and then select from the following options:

Monotone. Uses one color to generate image tone (limited dynamic range).
Duotone. Uses two colors to generate image tone (better dynamic range for B&W images).
Tritone. Uses three colors to generate image tone (great dynamic range, with a variety of color combinations).
Quadtone. Uses four colors to generate image tone (best dynamic range, practically unlimited color choices).

Click the Overprint Colors button to adjust how the colors will display when the inks are printed.

Click OK.

Using Multi-Channel Color Mode

PS 1.3

The Multi-Channel color mode is a specialized mode. Images converted into multi-channel color mode, converts the original color channels into shades of gray, with the grays based on the original luminosity values of the original image, and the original channels are converted into spot colors. Since multi-channel mode is used almost exclusively by the printing industry, converting a CMYK image into multi-channel color mode, produces Cyan, Magenta, Yellow, and Black spot channels, and converting an RGB image produces Cyan, Magenta, and Yellow spot channels, minus the Black channel. In both instances, converting to Multi-channel causes the loss of the mixing, or Composite channel.

Use the Multi-Channel Color Mode

Open an image.

Click the Image menu, point to Mode, and then click Multi-Channel.

Photoshop converts the image into the Multi-Channel mode.

Important

Images converted to the multi-channel mode, must be saved in the DCS 2.0 format (Digital Color Separation). The DCS 2.0 format generates a separate file for each of the multi-channel’s spot colors.

Using the Replace Color Adjustment

Photoshop’s Replace Color command lets you create a selection, based on image color, and replace that color selection with any other color. The Replace Color adjustment accomplishes this by giving you access to the three items that control color: Hue, Saturation, and Brightness. Hue gives you the ability to change the images physical color, Saturation controls the amount of color, and Brightness determines how bright the color is, based on its Hue and Saturation.

Use the Replace Color Adjustment

Open a color document.

Click the Image menu, point to Adjustments, and then click Replace Color.

Click on the active document using the Selection eyedroppers to select, add, or subtract colors.

Click the Color box to select a specific color for the selection.

Drag the Fuzziness slider to increase or decrease the sensitivity of the eyedropper tools.

Click the Selection or Image option to toggle between a view of the selection mask and the active image (white areas of the mask represent selection).

Drag the Hue, Saturation, and Lightness sliders to change the selected areas.

Select the Preview check box to view the changes in the active document.

Click OK.

Working with the Color Palette

Photoshop not only lets you select virtually any colors you desire, it also lets you store those colors for future use. For example, you create a color scheme for a recurring brochure and you want a way to save those colors, or you’re working on an Internet graphic and you need a Web-safe color palette. Whatever your color needs, Photoshop stands ready to meet them. The Color palette gives you access to Photoshop’s color generation tools. This single palette lets you create colors using 6 different sliders sets, 2 spectrum color selectors, a grayscale ramp, and an option that lets you create a color ramp for the current foreground and background colors.

Work with the Color Palette

Select the Color palette.

Click the Color Options button.

Select from the following Color Sliders:

Grayscale. Creates a single slider going from white (0) to black (100).
RGB. Creates three sliders (red, green, and blue). Each slider has a possible value from 0 to 255.
HSB. Creates three additive sliders (hue, saturation, and brightness). Each slider has a possible value from 0 to 255.
CMYK. Creates four subtractive sliders (cyan, magenta, yellow, and black). Each slider has a possible value from 0 to 100.
Lab. Creates three sliders (L, a, and b). The L slider has a possible value from 0 to 120, and the a, b sliders have a possible value from -120 to 100.
Web Color. Creates three sliders (red, green, and blue). Each slider has a possible hexadecimal value from 00 to FF.

Click the Color Options button, and then select from the following Spectrums or Ramps:

RGB. Converts the lower portion of the Color palette to the RGB spectrum. Clicking anywhere in the spectrum changes the active color.
CMYK. Converts the lower portion of the Color palette to the CMYK spectrum. Clicking anywhere in the spectrum changes the active color.
Grayscale. Converts the lower portion of the Color palette to grayscale ramp. Clicking anywhere in the ramp changes the active color.
Current Colors. Converts the lower portion of the Color palette to a color ramp, using the current foreground and background colors. Clicking anywhere in the ramp changes the active color.

To conform the color ramp to the Web safe palette, click the Color Options button, and then click Make Ramp Web Safe.

To change a color using the Adobe Color Picker, double-click a color box, select a color using the color range or color mode options, and then click OK.

You can choose colors using four color models: HSB, RGB, Lab, and CMYK.

For Your Information: Understanding Spectrums and Ramps

Spectrums and Ramps are located at the bottom of the Color palette, and represent the entire spectrum for the chosen color space. For example, the CMYK spectrum displays a rainbow of colors in the CMYK color gamut. Moving the eyedropper into the spectrum box and clicking lets you select any color, as well as giving you a visual representation of the relationships between various colors. The Grayscale Ramp gives you linear access to the 256 values of available grayscale.

Working with the Swatches Palette

Photoshop not only lets you select virtually any colors you desire, it also lets you store those colors for future use. Where the Color palette lets you select virtually any color you need, the Swatches palette, lets you save and use swatch palettes. By default, the Swatches palette holds 31 pre-defined color palettes, and has the ability to hold as many user-defined palettes as you desire.

Add a Color Swatch to the Swatches Palette

Select the Swatches palette.

Click the Swatches Options button, and then choose from the 31 predefined color palettes.

Click the Append button to add the selected color palette.

Change and Delete Colors on the Swatches Palette

Select the Swatches palette.

Select a color, and then change the following:

Foreground. Change the color by clicking on any color in the Swatches palette.
Background. Change the color by holding down the Ctrl (Win) or (Mac) key, and then clicking on any color in the Swatches palette.
Delete. Hold down the Alt (Win) or Option (Mac) key, and then click the color in the Swatches palette.

Add Colors to the Swatch Palette

Select the Color palette, and then drag the sliders or enter values to create a new color swatch.

Select the Swatches palette, and then drag the lower-right corner to expand its size beyond the range of the available colors.

Move the cursor just below the last swatch color until it resembles a paint bucket.

Click once, name the color, and then click OK.

Save Customized Swatch Palettes

Select the Swatches palette.

Create a customized swatch palette by adding and/or deleting colors from an existing palette.

Click the Swatches Options button, and then click Save Swatches.

Enter a name in the Save As box.

Click the Where (Mac) or Save In (Win) list arrow, and then select a location to store the swatch.

Click Save.

Did You Know?

You can access your customized swatch palettes from the Swatches Options button. When you save Swatch Palettes in the Color Swatches folder (default location), your customized swatch palettes appear at the bottom of the Swatches Options menu.

Using the Stroke and Fill Commands

Photoshop gives you many choices when it comes time to add or modify the colors of a document—paint brushes, airbrushes, and drawing tools, just to name a few. Two little used but powerful tools are the Stroke and Fill Commands. Both the Stroke and Fill commands work with selection tools. For example, you may want to create a unique stoke around an object, or fill a specific area of a document with a color or pattern. If that’s the case, then the Stroke and Fill commands are the best and quickest ways to perform those operations.

Create a Stroke

Create a selection using any of Photoshop’s selection tools, or really get fancy and make a selection from one of Photoshop’s Shape drawing tools.

Timesaver

To further control the process, perform the stroke (or fill) operations within a new layer.

Click the Edit menu, and then click Stroke.

Enter a Width value (1 to 250) for the stroke.

Click the Color box, and then select a color (the color box defaults to the foreground color).

Select a location option (Inside, Center, or Outside) for the stroke of the selection marquee.

Click the Mode list arrow, and then select a blending mode.

Enter an Opacity percentage value (0 to 100) for the stroke.

Select the Preserve Transparency check box to protect any transparent image areas (if there are no transparent areas, this option is disabled).

Click OK.

Create a Fill

Create a selection using any of Photoshop’s selection tools.

Click the Edit menu, and then click Fill.

Click the Use list arrow, and then select a fill option:

Foreground Color
Background Color
Color
Pattern
History
Black
50% Gray
White

Click the Mode list arrow, and then select a blending mode.

Enter an Opacity value (0 to 100) for the stroke.

Select the Preserve Transparency check box to protect any transparent image areas (if there are no transparent areas, this option is disabled).

Click OK.

Did You Know?

You can use the Fill command for more than filling an area with a solid color or unique pattern. For example, selecting a sepia color, and changing the Fill Blending mode to Color, tints the selected area with sepia, creating an old-style, sepia-toned image. Experiment with the Fill blending modes to create unique image effects.

Creating Spot Color Channels

When you work in the world of service bureaus and press machines, there are certain things you must do to create a printable document. The color mode of the image will be CMYK, and the output of the document will most likely be in a format designed to create color plates such as DCS 2.0 (Digital Color Separation). In addition, you may want to apply a spot color to the image. Spot colors instruct a press to apply a specific color to a specific portion of a document. For example, you may want to create a book cover jacket, and you want the author’s name in a specific Pantone Blue, or want to apply a varnish to a portion of a brochure. Whatever the case, you will need to create a spot color channel.

Create a Spot Color Channel

Open a document.

If the document is not in the CMYK format, click the Image menu, point to Mode, and then click CMYK to convert it.

Create a selection, defining the area for the spot color. Use any of Photoshop’s selection tools, including the Type Mask tool.

Select the Channels palette.

Click the Channels Options button, and then click New Spot Channel.

Click the Color box, and then select a color.

If you need a specific press color, such as the Pantone Color Matching System, click the Custom button in the Color Picker, select from the available color sets, and then click OK.

The Name box displays the name of the selected color.

Enter a Solidity value (0 to 100) to view the spot color at a specific opacity (Solidity does not affect press output).

Click OK.

Using the Variations Adjustment

Photoshop’s Variations adjustment gives you a look at how working with analogous and complimentary colors impacts the color in a Photoshop document. For example, if an image has an overall green cast, it needs additional magenta. Understanding how colors interact and work to produce different colors helps you decide the correct course of action to take, and the Variations adjustment is an excellent teacher.

Use the Variations Adjustment

Open a document.

Click the Image menu, point to Adjustments, and then click Variations.

The Original and Current Pick are displayed in the upper-left portions of the Variations dialog box.

To restore the image, click Original any time during the adjustment process.

Click the Shadows, Midtones, Highlights, or Saturation options to apply a color shift.

Drag the Fine/Coarse slider to determine how much change occurs with each adjustment.

Select the Show Clipping check box to display a mask over areas of the image outside of the CMYK printable color space.

Click the color thumbnails surrounding the image to add specific colors to the Current Pick.

Click Lighter or Darker to change the brightness of the image.

Click OK.

Using the Levels Adjustment and Command

PS 2.3

Through interactive feedback using a Histogram, the Levels adjustment gives you live information about the tonal values in the active image. It’s an excellent tool to perform overall tonal adjustments, and some color correction. Auto Levels is considered a quick fix color adjustment which, in some cases, works just as well as manually correcting color. However, with all the problems that exist in the average photo, it’s always best to manually adjust an image. Since the Auto Levels command relies on information contained within the image—information that is sometimes inaccurate—it’s usually best to correct the image manually using the Levels Adjustment command.

Use the Levels Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Levels.

Click the Channel list arrow, and then select the composite channel.

Drag the Input Level sliders to adjust the brightness level.

Drag the Output Level sliders to adjust the level of ink sent to the output device (printer).

Click OK.

Use the Auto Levels Command

Open an image.

Click the Image menu, point to Adjustments, and then click Auto Levels.

If you don’t like what you see, don’t forget you have the ability to use undo.

Using the Auto Contrast and Color Commands

PS 2.3, 2.4

The Auto Contrast command adjusts the tonality of the image without impacting color. The Auto Color command adjusts the tonality and color of the image by ignoring channels and looking directly at the image. The automatic color commands receive their adjustment queues from information within the active image, including any erroneous color information. For example, if the image contains a large border (typically white), the auto commands will factor that information into the correction of the image. It’s best to correct any dust, and scratch problems, and crop out any borders before applying the auto contrast and color commands.

Use the Auto Contrast Command

Open an image.

Click the Image menu, point to Adjustments, and then click Auto Contrast.

Important

Use the Auto buttons (Levels, Contrast, Color) buttons only if you do not understand how to manually control the image using powerful adjustments, such as Levels and Curves.

Use the Auto Color Command

Open an image.

Click the Image menu, point to Adjustments, and then click Auto Color.

Did You Know?

You can use a selection to define how the Auto Contrast and Auto Color commands work. If the image contains a border, and you don’t want the Auto command using the border to influence the correction, simply select the Rectangular marquee and draw a border around the image. When the Auto command is applied, only the selected areas will be adjusted.

Using Curves and Color Adjustments

PS 2.3

The Curves adjustment (New!) lets you adjust tonal ranges in the image without changing image exposure. Curves is an excellent adjustment for lightening the dark shadows of an image to bring out detail, or for creating special effects like solarization. The Color Balance adjustment lets you change the highlight, shadows, and midtones of an image separately. The Color Balance dialog box performs linear adjustments to color; therefore, it’s a good tool for correcting common tonal adjustments, such as using traditional outdoor film, indoors and getting a green cast to the image. The Brightness/Contrast adjustment changes an image by an overall lightning or darkening of the image pixels. While good for special effects, its linear way of changing an image’s brightness and contrast do not lend themselves to photo restoration. Curves and Levels are much better for this type of work.

Use the Curves Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Curves.

To select preset mix levels (New!), click the Preset list arrow, and then select the preset you want.

Click the Channel list arrow, and then select the composite channel.

Click the Tonal Input bar to reverse the Curves tonal values.

Click on the diagonal line to add an edit point, and then drag up or down to increase or decrease the tonal values of the active image.

Use the Eyedropper tools to select tonal values directly in the active image window.

Select the Preview check box to view changes to the image.

Click the curve option to adjust the curve by adding points or click the pencil option to draw a curve.

To save settings (New!), click the Preset Options button, click Save Presets, type a name, and then click Save.

Click OK.

Use the Color Balance Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Color Balance.

Drag the CMYK to RGB sliders to adjust the color.

Click a Tone Balance option.

Click OK.

Use the Brightness/Contrast Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Brightness/Contrast.

Drag the Brightness slider left to decrease the brightness values or right to increase the values of the colors in the active image.

Drag the Contrast slider to the left to decrease the color steps or left to increase the steps in the image.

Click OK.

Did You Know?

You can use selection to control the Brightness/Contrast adjustment. Use any of Photoshop’s selection tools to isolate a portion of the image before using the Brightness/Contrast adjustment, and then only the selected areas will be adjusted.

For Your Information: Understanding Brightness and Contrast

The Brightness/Contrast adjustment performs linear adjustment to an image. For example, moving the brightness slider to the right will increase the brightness values of all the pixels in the image equally. Since photographs are not linear in nature, the Brightness/Contrast adjustment is not recommended for use on images. For images, use the Levels, and Curves (non-linear) adjustments, and use Brightness/Contrast for clipart, text, and non-photographic images.

Using the Hue/Saturation and Desaturate Commands

The Hue/Saturation adjustment gives you separate control over an image’s Hue, Saturation, and Brightness, and its Colorize option lets you apply a color cast to an image that’s similar to a duotone effect. The Desaturate command removes all the color from an image, which preserves the Hue and Brightness values of the pixels, and changes the Saturation value to zero. The result is a grayscale image.

Use the Hue/Saturation Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Hue/Saturation.

Drag the Hue, Saturation, and Lightness sliders to the level you want for your image.

Click the Edit list arrow, select a color, and then click inside the active image with the eyedropper tools to adjust the Hue/Saturation.

Select the Preview check box to see how your image looks.

Select the Colorize check box to color tint the image with the current foreground color.

Click OK.

Use the Desaturate Command

Open an image.

Click the Image menu, point to Adjustments, and then click Desaturate.

Did You Know?

You can Desaturate selected areas of an image using the Sponge tool. Click the Sponge tool, click Desaturate on the Options bar, and then drag to slowly remove color from the image.

Using the Match Color Adjustment

The Match Color adjustment lets you select colors in the image, and then match and change them—using Luminance, Color Intensity, and Fade sliders—to another image. The Match Color adjustment will only work on images in the RGB color mode. Match Color is a great tool to help you get that consistent look you’ll need when you need to match colors with your images.

Use the Match Color Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Match Color.

Drag the various sliders (Luminance, Color Intensity, and Fade) to adjust the image.

Select the Neutralize check box to automatically remove the color case in the active image.

Click the Image Statistics Source list arrow, and then select another image or layer for matching the color in the Destination Image.

If you select a portion of an image before entering the Match Color dialog box, you can choose whether to use the selection in the source or target document calculate the color match.

Click Save Statistics to save the current adjustment, or click Load Statistics to load adjustments made to other images.

Select the Preview check box to view changes to the active image.

Click OK.

Using the Selective Color Adjustment

The Selective Color adjustment is designed to give you the ability to add or subtract specific amounts of cyan, magenta, yellow, and black inks. An excellent tool for making adjustments to an image based on a color proof, or for adding/subtracting certain primary colors; based on information supplied by your printer.

Use the Selective Color Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Selective Color.

Click the Colors list arrow, and then click the specific color to adjust.

Drag the Cyan, Magenta, Yellow, and Black sliders to the right or left to decrease or increase the color values.

Click the Relative option to change the selected color using a percentage of the color’s total ink.

Click the Absolute option to change the existing color using an absolute value of 1 to 100 percent.

Select the Preview check box to view changes to the active image.

Click OK.

Using the Channel Mixer Adjustment

The Channel Mixer (New!) adjustment is the tool of choice for adjusting individual color channels, or for making an image conversion to black and white. The Channel Mixer adjustment modifies the selected output channel by blending it with a mix of the existing image color channels. Since color channels record information using shades of gray, you’re essentially adding or subtracting grayscale information, not color information like the Selective Color adjustment. That’s what makes the Channel Mixer adjustment ideal for converting images into grayscale.

Use the Channel Mixer Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Channel Mixer.

To select a set of preset mix levels, click the Preset list arrow, and then select the preset you want.

Click the Output Channel list arrow, and then select from the available output channels.

Drag the Source Channel sliders right or left to increase or decrease the colors in the active image.

Drag the Constant slider left or right to adjust the grayscale output of the active image.

Dragging to the left adds more black to the image; dragging to the right adds more white.

Select the Monochrome check box to convert the colors of the image into shades of gray.

Select the Preview check box to view changes to the active image.

To save settings (New!), click the Preset Options button, click Save Presets, type a name, and then click Save.

Click OK.

Using the Gradient Map Adjustment

PS 2.5

The Gradient Map adjustment replaces the tonal values of the image with the colors supplied by a gradient. It’s a great tool for generating special color effects. In addition, the Gradient Map adjusts the active image’s colors to the colors of the selected gradient; taking the shadows of the image and mapping them to one endpoint of the gradient, and the highlights to the other point.

Use the Gradient Map Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Gradient Map.

Click the Gradient Used For Grayscale Mapping list arrow to adjust the gradient.

Select or clear the Dither or Reverse check boxes for the Gradient Options.

Select the Preview check box to view changes to the active image.

Click OK.

Using the Photo Filter Adjustment

The Photo Filter adjustment lets you apply a specific filter or color to an image. Applying the Photo Filter adjustment to an image is similar to placing a colored filter in front of a camera lens. Photographers use filters to help correct color problems associated with unique lighting conditions—early morning sunlight or indoor florescent lighting—you can use Photoshop’s Photo Filter adjustments to get the same results.

Use the Photo Filter Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Photo Filter.

Click the Filter option, click the Filter list arrow, and then select from the available color filter options.

Click the Color option to select a user-defined color filter.

Drag the Density slider left or right to adjust the intensity of the filter effect on the active image.

The higher the value, the greater the effect.

Select the Preserve Luminosity check box to preserve the color of the image highlights.

Select the Preview check box to view changes to the active image.

Click OK.

Using the Shadow/Highlight Adjustment

The Shadow/Highlight adjustment lets you quickly correct the problems associated with the over and under-exposed areas of an image such as deep shadows or bright highlights. In addition, the Shadow/Highlight adjustment makes quick work out of images that have really dark shadows or overexposed areas by adjusting the problem areas without changing the middle range of the image. The Shadow/Highlight adjustments will not work on images in the CMYK color mode.

Use the Shadow/Highlight Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Shadow/Highlight.

If necessary, select the Show More Options check box to display Highlights and Adjustments options.

Drag the Shadows Amount, Tonal Width, and Radius sliders right or left to adjust the shadow areas of the active image.

Drag the Highlights Amount, Tonal Width, and Radius sliders right or left to adjust the highlight areas of the active image.

Drag the Adjustments Color Correction and Midtone Contrast sliders left or right to decrease or increase the color saturation values of the adjusted areas of the image.

Enter values from 0 to 50 percent in the Black Clip and White Clip boxes to indicate how much of the shadow and highlight values will be clipped in the new image. Greater values produce images with more contrast.

Select the Preview check box to view changes to the active image.

Click OK.

Using the Exposure Adjustment

Photoshop’s Exposure adjustment is primarily designed for performing tonal adjustments to 32-bit High Dynamic Range (HDR) images, but it works with 8-bit and 16-bit images as well. Exposure works by changing an image using a linear color space (gamma 1.0) not the image’s current color space. When used with HDR images, it gives you the ability to draw out details of the image that otherwise might be completely lost within the shadows and highlights.

Use the Exposure Adjustment

Click the Image menu, point to Adjustments, and then click Exposure.

Select from the following options:

Exposure. Adjusts the highlight end of the image’s tonal scale with little effect in the extreme shadows.
Offset. Darkens the shadows and midtones with little affect on the highlights.
Gamma. Adjusts the image gamma, using a simple power function. Similar to adjusting the mid points in an image’s brightness.

Use the eyedroppers to adjust the image’s luminance values only; not all the color channels, such as Levels, or Curves.

Black. Sets the Offset, shifting the pixel you click to zero, or pure black.
White. Sets the Exposure, shifting the point you click to pure white.
Midtone. Sets the Exposure, making the value you click middle gray.

Select the Preview check box to view changes to the active image.

Click OK.

Using the Invert and Equalize Commands

The Invert command reverses the colors and tonal values to their opposite values; in effect creating a negative. The Equalize command exaggerates the contrast between similar color values. It’s useful in finding stray pixels in a seemingly solid color area, or for a special color effect.

Use the Invert Command

Open an image.

Click the Image menu, point to Adjustments, and then click Invert.

The brightness values of each image channel are reversed, creating a negative color or grayscale image.

Use the Equalize Command

Open an image.

Click the Image menu, point to Adjustments, and then click Equalize.

The brightness values of the image pixels are distributed in a way that more accurately represents the entire range of brightness levels from white to black.

Using the Threshold and Posterize Adjustments

The Threshold adjustment splits an image into black and white, based on the original brightness levels of the pixels. It’s useful for locating the darkest and lightest pixels in an image, or for creating some great looking black and white special effects. The Posterize adjustment creates a simpler image by reducing the number of colors. It’s useful for creating an image with a clipart look, or for reducing the number of colors in preparation for the Web.

Use the Threshold Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Threshold.

Drag the Threshold slider to the right or left to change the point in which black and white are defined.

For example, setting the threshold slider to a value of 75 creates an image where all pixels with a brightness value of 75 or less are black, and all pixels with a value of 76 or higher are white.

Click OK.

Use the Posterize Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Posterize.

Drag the slider to select a Levels value (2 to 255) to define the number of colors used.

Lower values produce less colors, and more visual contrast.

Click OK.

Using the Black & White Adjustment

PS 2.3

The Black & White adjustment (New!) allows you to convert a color image to grayscale. During the adjustment process you can control how individual colors (Reds, Yellows, Greens, Cyans, Blues, and Magentas) are converted. You can also apply a tint to the grayscale image by adjusting hue and saturation color tones, which is similar to using the Channel Mixer. If you’re not sure how or where to start, you can use the Auto button to set grayscale values based on maximizing the distribution of gray values.

Use the Black & White Adjustment

Open an image.

Click the Image menu, point to Adjustments, and then click Black & White.

To select a set of preset mix levels, click the Preset list arrow, and then select the preset you want.

To set auto adjustments, click Auto.

Drag the Reds, Yellows, Greens, Cyans, Blues, and Magentas sliders to the level you want for your image.

Alt+click (Win) or Option+click (Mac) a color box to reset a slider to its initial setting.

To adjust the tint, select the Tint check box.

If you selected the Tint check box, adjust the Hue and Saturation.

Click OK.

Did You Know?

You can save Black & White mix levels. In the Black and White dialog box, adjust the levels you want, click the Preset Options button, click Save Preset, type a name, and then click Save.

..................Content has been hidden....................

You can't read the all page of ebook, please click here login for view all page.

Table of Contents for 8. Understanding Colors and Channels

Create new playlist

Sign In

Sign Up