Press Ctrl+3 to sidle up to the Display & Cursors options, which appear in Figure below.

These options affect the way colors and cursors appear on screen. Here’s how the options work, along with recommended settings:

• Color Channels in Color (off): An individual color channel contains just 8 bits of data per pixel, which makes it equivalent to a grayscale image. Photoshop provides you with the option of colorizing the channel according to the primary color it represents.

For example, when this option is turned on, the red color channel looks like a grayscale image viewed through red acetate. Most experts agree the effect isn’t helpful, though, and it does more to obscure your image than make it easier for you to see what’s happening. Leave this check box turned off.

• Use Diffusion Dither (on): Here’s an option for you folks working on 8-bit screens that display no more than 256 colors at a time. To simulate the 16-million-color spectrum on a 256-color screen, Photoshop automatically jumbles colored pixels using a technique called dithering.

This option controls the pattern of dithered pixels. Photoshop offers a naturalistic “diffusion” dither that looks nice on screen. But because the diffusion dither follows no specific pattern, you sometimes see distinct edges between selected and deselected portions of your image after applying a filter or some other effect.

You can eliminate these edges and resort to a more geometric dither pattern by turning off this check box. Turning off the Use Diffusion Dither check box is an awfully drastic (not to mention ugly) solution, though. The better way to eliminate the occasional visual disharmony is to force Photoshop to redraw the entire image.

You can press Ctrl+Alt+0 or perform some other zoom function. Note that a related option found in earlier versions of Photoshop, Use System Palette, is gone.

When you set your monitor to display 256 colors or less, this option let you specify whether you wanted Photoshop to use the default monitor palette or to adjust the palette constantly to best suit your image. The latter choice is no longer available.

• Use Pixel Doubling (off): This option can help speed up operations when you’re editing huge images on a less-than-robust computer, but not by much. When you select the option, Photoshop displays selected areas using a low resolution proxy. Although the option previously was connected just to moving layers, it now affects selections, too.

• Painting Cursors (Brush Size): When you use a paint or edit tool, Photoshop can display one of three cursors. The default Standard cursor looks like a paintbrush, airbrush, finger, or whatever tool you are using. These cursors are great if you have problems keeping track of what tool you selected, but otherwise they border on childish.

The Precise and Brush Size options are more functional. The Precise option displays a cross-shaped cursor called a crosshair regardless of which tool is active. The crosshair is great because it prevents the cursor from blocking your view as you edit.

Meanwhile, the Brush Size option shows the actual size and shape of the active brush in the Brushes palette. Most artists prefer this final setting to the others because it comes the closest to showing the cursor the way it really is.

When Standard or Brush Size is selected, you can access the crosshair cursor by pressing the Caps Lock key. When Precise is selected from the Painting Cursors options, pressing Caps Lock displays the brush size.

• Other Cursors (Standard): Again, you can select Standard to get the regular cursors or Precise to get crosshairs. I prefer to leave this option set to Standard because you can easily access the crosshair cursor by pressing Caps Lock. The Precise option locks you into the crosshair whether or not you like it.

Transparency & Gamut

Press Ctrl+4 to switch to the Transparency & Gamut panel shown in Figure below.

The options in this panel change how Photoshop displays two conceptual items transparent space behind layers and RGB colors that can’t be expressed in CMYK printing. The options are arranged into two groups Transparency Settings and Gamut Warning as explained in the following sections.

Transparency Settings

Just as the Earth spins around in empty space, a Photoshop image rests on a layer of absolute transparency. By default, Photoshop represents this transparency as a gray checkerboard pattern. (What better way to demonstrate nothingness? I might have preferred a few lines from a Jean-Paul Sartre play, but no matter.)

You may get a brief glimpse of this checkerboard when you first open an image or switch to Photoshop from another application. When you view a layer independently of others, Photoshop fills the see-through portions of the layer with the checkerboard. So having the checkerboard stand out from the layer itself is essential.

You can customize the size of the checkers and the color of the squares using the Grid Size and Grid Colors pop-up menus. You can also click the color swatches to define your own colors. To lift colors from the image window, move your cursor outside the Preferences dialog box to get the eyedropper.

Click a color to change the color of the white checkers; Alt-click to change the gray ones. If you own a TrueVision NuVista+ board or some other 32-bit device that enables chroma keying, you can select the Use Video Alpha check box to view a television signal in the transparent area behind a layer. Unless you work in video production, you needn’t worry about this option.

Gamut Warning

If Photoshop can display a color on screen but can’t accurately print the color, the color is said to be out of gamut. You can choose View>Gamut Warning to coat all out-of-gamut colors with gray.

I’m not a big fan of this command View>Proof Colors (Ctrl+Y) is much more useful but if you use View>Gamut Warning, you don’t have to accept gray as the out-of-gamut coating. Change the color by clicking the Gamut Warning Color swatch, and lower the Opacity value to request a translucent coating.

Units & Rulers

The Units & Rulers panel is the fifth panel in the Preferences dialog box; hence, you reach the panel by pressing Ctrl+5. Shown in Figure below, this panel offers options that enable you to change the predominant system of measurement used throughout the program.

Whenever the rulers are visible, the Units & Rulers panel is only a double-click away. Choose View>Show Rulers (Ctrl+R) to see the rulers on screen and then double-click either the horizontal or vertical ruler.

Rulers

You can set the unit of measurement via the Units option in the Preferences dialog box. But in Version 6, there’s an easier way: Just right-click anywhere on the ruler to display a pop-up menu of unit options and then click the unit you want to use.

You can display the same pop-up menu by clicking the plus sign in the lower-left corner of the Info palette. When you’re first learning Photoshop, going with inches or picas is tempting, but experienced Photoshop artists use pixels.

Because you can change the resolution of an image at any time, the only constant is pixels. An image measures a fixed number of pixels high by a fixed number of pixels wide—you can print those pixels as large or as small as you want.

Type

Photoshop 6 enables you to set the unit of measure used for the type tool and its palettes independently of the ruler units. You can work in points, pixels, and millimeters; select your unit of choice from the Type pop-up menu.

Column Size

The Column Size options enable you to size images according to columns in a newsletter or magazine. Enter the width of your columns and the size of the gutter into the Width and Gutter option boxes. Then use File>New or Image>Image Size to specify the number of columns assigned to the width of the image.

Point/Pica Size

The last option in the Units & Rulers panel may be the most obscure of all Photoshop options. In case you aren’t familiar with points and picas, exactly 12 points are in a pica, and about 6.06 picas are in an inch.

Well, because picas are almost evenly divisible into inches, the folks who came up with the PostScript printing language decided to bag the difference and to define a pica as exactly 1⁄6 inch. This makes a point exactly 1⁄72 inch.

But a few purists didn’t take to it. They found their new electronic documents weren’t quite matching their old paste-up documents and, well, I guess life pretty much lost its meaning. So Adobe had to go back and add the Traditional (72.27 points/inch) option to keep everyone happy.

I prefer the nontraditional PostScript definition of points. This way, a pixel on screen translates to a point on paper when you print an image at 72 ppi (the standard screen resolution).

Call me a soulless technodweeb, but computer imaging makes more sense when you can measure points and pixels without resorting to a calculator. The old ways are dead; long live the 1⁄72-inch point!

Guides & Grid

Someone at Adobe said, “Let the preference settings continue.” And, lo, there is Guides & Grid, which can be accessed by all who press Ctrl+6 and viewed by all who cast an eye on Figure below.

This panel lets you modify the colors of the guides and specify the size of the grid. You can display the Preferences dialog box and go directly to the Guides & Grid panel by double-clicking a guide with the move tool or Ctrl-double-clicking with another tool. (To create a guide, drag from the horizontal or vertical ruler into the image.)

Guides

Select a color for horizontal and vertical ruler guides from the Color pop-up menu. To lift a color from the image, move your cursor outside the Preferences dialog box and click in the image window with the eyedropper. You can also view guides as solid lines or dashes by selecting an option from the Style pop-up menu.

Grid

Select a color for the grid from the Color menu, or Alt-click in the image window to lift a color from the image. Then decide how the grid lines look by selecting a Style option. The Dots setting is the least intrusive.

The “Gridline every” value determines the increments for the visible grid marks on screen. But the Subdivisions value sets the real grid. For example, if you request a grid mark every one inch with four subdivisions—as in Figure above—Photoshop snaps selections and layers in quarter-inch increments (one inch divided by four).

Plug-Ins & Scratch Disk

Press Ctrl+7 to advance to the panel shown in Figure below.

Each time you launch Photoshop, the program searches for plug-in modules and identifies one or more scratch disks. You have to tell Photoshop where to find the plug-ins and where the temporary scratch files should go.

Additional Plug-Ins Directory

By default, the plug-ins are located in a folder called Plug-Ins, which resides in the same folder as the Photoshop application. But you can tell Photoshop to also look for plug-ins in some other folder a handy option if you install all your third-party plugins to some central location outside the Photoshop folders. To specify the second plug-ins location, select the check box and then click Choose to select the folder.

Scratch disks

By default, Photoshop assumes you have only one hard disk, so Photoshop stores its temporary virtual memory documents called scratch files on the same disk that contains your system software. If you have more than one drive available, though, you might want to tell Photoshop to look elsewhere.

In fact, Photoshop can use up to four drives. For example, one of my computers is equipped with two internal hard drives:

• A 2GB drive, C:, contains the system and most of the workaday documents I create.

• The other drive is a 4GB device partitioned into two 2GB segments. These are formatted as the D: and E: drives. D: contains all my applications while E: remains largely empty except for a few large miscellaneous files—QuickTime movies, digital camera snapshots, weird plug-ins that I haven’t gotten around to backing up yet.

E: has the most free space, so I set it as the First scratch disk. On the off chance that my images get so huge that Photoshop fills up E: and has to look elsewhere for scratch space, I select D: from the Second pop-up menu and my main system drive, C:, from the Third.

That’s the end of my drives, so Fourth remains set to None. Adobe advises against using removable media such as SyQuest, MO, and Zip drives—as a scratch disk. Removable media is typically less reliable and slower than a permanent drive. (A Jaz cartridge is more stable than Zip or the others, but still not as reliable as a fixed hard drive.)

Using a removable drive on an occasional basis isn’t the end of the world, but if you use it regularly you may end up crashing more often, in which case you’ll probably want to add a new hard drive.

Changes affect the next session

As the note at the bottom of the Plug-ins & Scratch Disks panel warns, the settings in this panel don’t take effect until the next time you launch Photoshop. This means you must quit Photoshop and restart the program. There’s nothing more frustrating than knowing that the options in this dialog box are set incorrectly before you’ve even started up Photoshop.

It means you have to launch Photoshop, change the settings, quit Photoshop, and launch the program again. What a waste of time! That is, it would be a waste of time if there wasn’t a workaround. Fortunately, you can access the plug-ins and scratch disk settings during the launch cycle.

After double-clicking on the Photoshop application icon or choosing Photoshop from the Start menu, press and hold the Ctrl and Alt keys. After a few seconds, a screen of the scratch disk options appears. Specify the disks as desired and press Enter. Your new settings now work for the current session no restarting necessary.

Image Cache

Ever since Photoshop 3 came out, Adobe has received a fair amount of flack from high-end users who demand faster image handling. Programs such as Live Picture and xRes take seconds to apply complex operations to super-huge photographs, while Photoshop putters along for a minute or more.

Granted, Live Picture and xRes aren’t nearly as capable as Photoshop, but they are faster. The good news is that Photoshop sports a caching scheme that speeds operations at reduced view sizes. You can adjust this feature by pressing Ctrl+8 in the Preferences dialog box. This displays the Memory & Image Cache panel, shown below.

Cache Levels

Photoshop has been criticized for its lack of a “pyramid-style” file format, such as Live Picture’s IVUE or xRes’s LRG. Both IVUE and LRG store an image several times over at progressively smaller and smaller image sizes, called downsamplings.

For example, the program would save a full view of the image, a 50 percent view, a 25 percent view, and so on. Live Picture or xRes can then load and edit only the portion of the image visible on screen, greatly accelerating functions.

Photoshop’s alternative is image caching. Rather than saving the downsamplings to disk, Photoshop generates the reduced images in RAM. By default, the Cache Levels value is set to 4, the medium value. This means Photoshop can cache up to four downsamplings at 100, 50, 25, and 12.5 percent which permits the program to apply operations more quickly at reduced view sizes.

For example, if you choose a color correction command at the 50 percent view size, it previews much faster than normal because Photoshop has to modify a quarter as many pixels on screen.

However, Photoshop must cache downsamplings in RAM, which takes away memory that could be used to hold the image. If you have lots of RAM (128MB or more) and you frequently work on large images (20MB or larger), you’ll probably want to raise the value to the maximum, 8.

The lost memory is worth the speed boost. If you have little RAM (say, 16MB or less) and you usually work on small images or Web graphics (4MB or smaller), you may want to reduce the Cache Levels value to 1 or 2. When files are small, RAM is better allocated to storing images rather than caching them.

Use cache for histograms

The “Use cache for histograms” check box tells Photoshop whether to generate the histograms that appear in the Levels and Threshold dialog boxes based on the cached sampling or the original image. A histogram is a bar graph of the colors in an image.

When you choose a command such as Image>Adjust>Levels, Photoshop must spend a few seconds graphing the colors. If you turn the Use Cache for Histograms check box on, Photoshop graphs the colors in the reduced screen view, which takes less time, but is also less accurate. Turn the check box off for slower, more accurate histograms.

Generally speaking, I say leave the option on. A histogram is merely a visual indicator and most folks are unable to judge the difference between a down sampled histogram and a fully accurate one.

Again, if you’re working in very large images and you have the Cache Levels value maxed out at 8, you should probably leave this check box selected. But if you have to reduce the Cache Levels value, turn off the check box. Histograms are the first thing that can go.

This option is not responsible for the histogram irregularities that popped up in Photoshop 4. The fact that the Threshold dialog box sometimes lifted its histogram from the active layer only was a bug, not a function of Use cache for histograms. Even so, this option has received a lot of flack it did not deserve. My opinion is that, on balance, this is a positive feature that should be left on.

Physical Memory Usage

Windows 95, NT 4, and later offer dynamic memory allocation, which means that each application gets the memory it needs as it needs it. But Photoshop is something of a memory pig and has a habit of using every spare bit of RAM it can get its hands on.

Left to its own devices, it might gobble up all the RAM and bleed over into Windows’ virtual memory space, which is less efficient than Photoshop’s own scratch disk scheme. The Physical Memory Usage option helps you place some limits on Photoshop’s ravenous appetites.

The option lists the amount of RAM available to all applications after the operating system loads into memory. You can then decide how much of that memory should go to Photoshop.

If you like to run lots of applications at the same time your word processor, Web browser, spreadsheet, drawing program, and Photoshop, for example then set the Used by Photoshop value to 50 percent or lower. But if Photoshop is the only program running and if you have less than 32MB of RAM raise the value to 70 to 80 percent.

I recommend against taking the Used by Photoshop value any higher than 80 percent, particularly on a low-capacity machine (32MB or less). Doing so permits Photoshop to fill up RAM that the operating system might need, which makes for a less stable working environment.

As I’ve said before, if Photoshop is going too slow for you and hitting scratch disk too often, buy more RAM don’t play dangerous games with the little RAM you do have.