An edge is formed where adjacent pixels have high contrasting values.

Photoshop has a number of filters that detect these and apply contrast reducing or increasing effects to soften or sharpen the image accordingly.

The top half of the picture (2) is an enlarged part of the stem of the plant in the picture above (1).

The Find Edges filter picks up all the areas of edge contrast and produces an almost posterized version that highlights these edges (3).

Early on in the digital imaging revolution, users started to place visual effects like drop shadows or glowing edges on parts of their pictures.

With the release of later versions of Photoshop, these types of effects have become far more sophisticated and built-in features of the program. Now, it is possible to apply an effect like a ‘drop shadow’, or a bold outline, to the contents of a layer with the click of a single button. Some effects changes are applied to the layer contents, others create a new layer to store the effect.

In Photoshop these effects options are listed under the Layer > Layer Styles menu (1). Effects can be combined to produce some truly stunning and complex styles. Many example styles are supplied in Photoshop and are grouped in a single palette called Layer Styles (2). A thumbnail version of each style provides a quick reference to the results of applying the multiple effects.

To add the effect to a selected layer, simply double-click on the thumbnail or drag the thumbnail onto the image.

With some styles the effects can be applied to the one layer, selection or picture and the settings used to create the effects can be edited by double-clicking the ‘f ’ icon on the selected layer in the palette.

Layer styles (effects) that have been applied to a layer can be temporarily hidden from view by selecting the Hide All Effects command (2).

A small ‘f’ icon is displayed on the left end of any layers that currently have style applied (1).

The styles can be redisplayed using the Layer > Layer Style > Show All Effects command (3).

Hiding the effects of a picture differs from clearing them (Layer > Layer Style > Clear Layer Style), as this option deletes any effects or styles currently applied to the layer, rather than just removing them from view.

The Scale Effects command (Layer > Layer Style > Scale Effects) allows you to alter the look of the styles and effects applied to layers and text by altering their size and strength. The Scale slider adjusts the setting characteristics such as drop shadow, bevel edges and outline strokes from 1% of the original size up to 1000%. You can also scale effects with the Scale Styles option in the Image Size dialog box (1). These commands are particularly useful for adjusting the scale of styles and effects after reducing or increasing the original image size.

Standard digital photos contain three color channels - Red, Green and Blue (RGB). The vast number of colors we see in most pictures are created by mixing various tones of these three primary colors together.

The number of different tones possible in each channel is called the color depth of the file. Most photos have an 8-bit color depth, which means that each channel is capable of supporting 256 levels of tone. When you mix this number of tones of all three channels, it is possible to create over 16 million different colors in an 8-bit system.

Some digital cameras can capture pictures with higher bit modes, providing the possibility of even more tones per channel and therefore a greater number of colors overall.

By default Photoshop creates, enhances and edits 8-bit files, but the program also has the ability to edit and enhance 16-bit files and, with the release of CS2, make limited changes to 32-bit files as well.

Moving the tool tip over the picture surface whilst the Info palette is displayed shows the RGB values for each of the color channels (1).

By clicking and dragging the Elliptical Marquee tool on the picture surface, it is possible to draw oval-shaped selections.

Holding down the Shift key whilst using this tool restricts the selection to circle shapes, whilst using the Alt (Windows) or Options (Mac) keys will draw the selections from their centers.

A core part of a color managed editing system is the ability to save pictures so that they are tagged or have a color or ICC profile attached. The profile describes the color space that the picture was created in and allows the accurate representation of the colors and tones in the photo on screen and when printed.

Photoshop allows the saving or embedding of color profiles (in file formats that support the option) in both the Save for Web (2) and Save As (1) dialogs. An embedding or profile checkbox is contained in each of these dialogs.

To maintain the completeness of the color management system and the accurate representation of photos on your and other systems, ensure that this checkbox is always ticked.

This dialog box (1) appears when you open a picture that has an embedded profile that is different to the one you use for your working color space. You then have three options:

Use the embedded profile - This option maintains the original color profile that is associated with the image.

Convert document’s colors to the working space - Selecting this option makes a conversion between the existing color space and the one that you have currently selected as your working space.

Discard the embedded profile - This choice deletes the profile that is currently attached to the picture you are opening.

The actions that Photoshop follows when it encounters a profile mismatch situation is governed by the options in the Edit > Color Settings dialog (2). As a general rule always select the Ask When Opening item as this gives you the opportunity to decide which of the three ‘mismatch’ options is best to use for the scenario.

The Emboss filter, as one of the group of Stylize filters, uses the photo to recreate the look of embossed or beaten metal.

The edges in the picture are used as the basis for the effect with the three controls in the dialog providing adjustment over the strength and quality of the effect.

The Angle dial (1) alters the direction of the light used to provide highlight and shadow lines for the embossing. The Height slider (2) alters apparent depth of the embossing by increasing the size of the shadow and highlight detail, and the Amount control (3) varies the contrast and prominence of the effect.

A quick fix that can help brighten up a dark scanned or underexposed picture that cannot be improved using features like Auto Levels.

When you apply the Equalize command Photoshop redistributes the brightness values of the image’s pixels so that they more evenly represent the entire range of brightness levels. It does this by finding the brightest and darkest values in the image and then adjusts the levels so that the brightest value is white and the darkest value is black. It then equalizes the brightness by distributing the intermediate pixels evenly throughout the grayscale. You can also equalize just a selected area of an image by using one of the selection tools before you go to the Equalize menu. In this mode you also have the option of applying the values within that selected area to the whole photo. Equalizing the whole picture can sometimes overcompensate and darken the image (1), but making a selection of the important area and then choosing ‘Equalize entire image based on selected area’ can produce a better result (2).

The Eraser tool changes image pixels as it is dragged over them. If you are working on a background layer then the pixels are erased or changed to the background color. In contrast, erasing a normal layer will convert the pixels to transparent, which will let the image show through from beneath. As with the other painting tools, the size and style of the eraser is based on the selected brush tip - (1) Erasure with a hard-edged brush tip and (2) erasure with a soft-edged brush tip. But unlike the others the eraser can take the form of a paintbrush, pencil or block (Mode in the options bar). Setting the opacity will govern the strength of the Erasing action.

Apart from the straight Eraser tool, two other versions of this tool are available - the Background Eraser and the Magic Eraser. These extra options are found hidden under the Eraser icon in the toolbox. The Background Eraser is used to delete pixels around the edge of an object.

The tool pointer is made of two parts - a circle and a cross hair. The Magic Eraser uses the selection features of the Magic Wand to select similarly colored pixels to erase.

To use the Background Eraser tool, the cross hair is positioned and dragged across the area to be erased, whilst at the same time the circle's edge overlaps the edge of the object to be kept. The success of this tool is largely based on the contrast between the edge of the object and the background. The greater the contrast, the more effective the tool. Again, a Tolerance slider is used to control how different pixels need to be in order to be erased.

The Magic Eraser selects and erases pixels of a similar color from a picture. The selection part of the tool works in a similar way to the Paint Bucket or Lasso tools in that pixels are selected based on their color and tone.

The Contiguous setting forces the feature to select similar pixels that are adjacent to each other and the Tolerance value determines how alike the colors need to be before they are erased.

The Exclusion blending mode is one of the group of modes that base their effects on the differences between two pictures. This option is similar to the Difference mode but produces less dramatic and less contrasty results. When the upper layer is changed to the Exclusion mode the result displays the tonal difference between the two layers.

The difference is calculated by locating the lighter and darker pixels and then subtracting these from either of the two layers producing the resultant color.

Blending with a black top layer produces no change. Blending with a white top layer inverses the value of the bottom layer.

EXIF, or the Exchangeable Information Format, is a data format that is used for recording camera capture details and then displaying them inside software applications such as Photoshop. The information recorded by the camera and saved in this format can include shutter speed, aperture, camera model, date and time the photo was taken, exposure mode that the camera was set to and much more.

There are two places where you can view the available EXIF data for a picture:

In Bridge EXIF details are displayed as part of the greater metadata available for the picture. To display the metadata panel select the option from the View menu (1).

When working in the Photoshop workspace selecting the File > File Info option will display all the metadata associated with the picture including the camera-related EXIF data (2).

In addition, metadata entries can also be used as a means to sort images in the content area of Bridge using the options in the new Filter panel (3).

EXIF data is one part of a set of metadata information that can be viewed and, to some extent, edited and even created in Photoshop. Other metadata options include File Properties, IPTC or copyright information, edit history and any GPS details.

To exit or close the Photoshop program select File > Exit or File > Quit for Macintosh users.

If any files are open at the time of selecting the Exit command, a confirmation dialog will be shown asking the user if they want to save the file before quitting or cancel the action (1).

An active selection can be altered and adjusted using the options listed under the Select > Modify menu.

One option is the Expand command which increases the size of the selection by the number of pixels entered into the feature’s dialog (1).

If the selection incorporates part of the document edge this part of the marquee will not be changed by the command.

In Photoshop CS3 you can also access the Expand option via the Contract/Expand slider in the Refine Edge (2) feature. The preview options available in the Refine Edge dialog enable more accurate control over the Expand settings than using the tool with just the Expand Selection dialog.

The File > Export menu contains several different options for transporting information created or edited in Photoshop into formats that can be used by other programs or displayed on different hardware. The options are:

Data Sets as Files - Exports the data sets used in Photoshop files that contain data driven graphics options as files suitable for importing into a database or spreadsheet program.

Paths to Illustrator - Saves Photoshop paths as Illustrator documents.

Render Video (CS3) - Allows for the export of QuickTime video or image sequences. In Photoshop Extended you can also export timeline animations with video layers.

Send Video Preview to Device -Outputs the current image to a Firewire connected video device using the settings that were previously set in the Video Preview dialog.

Video Preview - Allows you to set the preview options that will be used to display the current image on a connected (via Firewire) video device.

Zoomify (CS3) or ZoomView (CS2)-This option converts the current image into the components necessary to display a Zoomify/ZoomView image in a web browser. The format is designed to deliver high resolution pictures via the web and this export option creates the Zoomify/ ZoomView components.

As with most programs that handle pictures and text, when you copy an item it is saved in the program’s clipboard. Photoshop is just the same, so pictures can be copied, stored temporarily on the computer’s clipboard and then pasted into other programs.

To use this option in Photoshop make sure that the Export Clipboard item is selected in the Edit > Preferences > General dialog (1).

As the storing of data on the Clipboard takes up RAM there is also an option to remove copied pictures using the Edit > Purge > Clipboard command (2).

Unlike other applications Photoshop manages its own clipboard and doesn’t use the one that is maintained by the operating system.

The Render Video option is available in the File > Export menu of the Extended version of Photoshop CS3. This feature is designed to work hand in hand with the new video and animation options in the program.

After importing a sequence of video file footage (File > Import > Video Frames to Layers) and editing/enhancing the frames in Photoshop CS3 Extended the final sequence can be written back to a video format with this option.

The Render Video dialog (1) has four distinct sections:

Location - determines the place on your computer where the rendered footage will be saved.

File Options - contains controls for the selecting QuickTime Presets (2), adjusting QuickTime settings (3), image sequence variables and document size.

Range - options for selecting all or part of the image sequence for rendering.

Render Options - specifies how the Alpha channel in the sequence is rendered and the frames rate of the resultant video.

Zoomify is an export to web utility used to create high quality zoomable pictures that are a fraction of their original size. Designed for photographers who don’t want to sacrifice the ability to show off the sharpness and quality of their high resolution captures for the convenience of web display, this feature creates all the necessary web components and saves them to a single folder and HTML page.

Users can preview the results of the Zoomify conversion by selecting the Open in Browser option at the bottom of the dialog before clicking the OK button.

Both the folder and display page need to be uploaded to a web server before being viewable on the internet.

Designed to be used exclusively with the new 32-bits per channel files the Exposure feature provides a mechanism for adjusting the contrast and brightness of the new HDR files.

The dialog contains three slider controls plus three eyedropper buttons. The Exposure (1) slider essentially controls the highlight and midtone areas of the picture and the Gamma (3) option adjusts the overall contrast. The Offset control

(2) alters the shadow and midtone areas without affecting the highlights.

The Eyedropper tools are used to set or ‘peg’ black, white and middle tone values and can be used in the same way that they are in the Curves and Levels features (4).

The Extract filter was first included in Photoshop back in version 5.5 of the program; where it was hidden away under the Image menu. Now the feature has pride of place in the first section of the Filter menu and provides users with a specialist Selection tool that removes the background from the surrounds of an object.

The concept is simple: draw around the outside of the object you want to extract, making sure that the highlighter overlaps the edge between background and foreground and then fill in the middle. The program then analyzes the edge section of the object using some clever fuzzy logic to determine what should be kept and what should be discarded, and ‘Hey Presto’ the background disappears.

The tool provides extracted objects faster than using the lasso or pen tools as you don’t need to be as accurate with your edge drawing, and it definitely handles wispy hair with greater finesse than most manual methods.

Extraction tips

• 1. When previewing the results you can refine the edges left by the extraction process using the Cleanup and Edge Touch up tools.
• 2. Make sure that the highlight slightly overlaps the object edges and its background.
• 3. For items such as hair, use a larger brush to encompass all strands.
• 4. Make sure that the highlight forms a complete and closed line around the object before filling.
• 5. Use the Smart Highlighting option to automatically locate the edge between foreground and background objects and to adjust the size of the highlighter to suit the clarity of the edge.

The Extrude filter, as one of the group of Stylize filters, projects the photo onto a series of extruded shapes that seem to explode from the middle of the document.

By altering the settings in the filter’s dialog you can choose the shape of the extrusions - blocks or pyramids (1). The size (2) and depth (3) of the extruded shapes can be set in pixels. Partly completed blocks can be masked or shown as part of the final image (4).

The Eyedropper tool is used to sample colors in a picture. After selecting the tool click on the color in the picture to set a new foreground color and Alt-click (Option-click for Macintosh) for a background color. The size of the area sampled can be adjusted using the options in the Sample Size menu in the options bar. Large pixel samples average the color and tone of the areas they select.