Flight Check: The Photoshop Settings
As we get ready for serious curvewriting, we need to check that several Photoshop defaults are set up properly. Some of these settings require Photoshop 6 or later; others will work with any version.
- First, double-click the eyedropper tool. In the Options bar at the top of the screen, the default is Point Sample. That's no good. It means that when measuring a color, Photoshop will report the value of the single pixel that's underneath the cursor. Since a single pixel may well be random noise, a piece of dust, or something else totally atypical, the measurement isn't reliable. Instead, as shown in Figure 3.4, set the preference to 3 by 3 average, which reports the average value of the nine pixels that surround the cursor. 5 by 5 average is also acceptable, but Point Sample is not.
Figure 3.4 Accurate measuring of color values with the Info palette requires a change in Photoshop's default eyedropper tool setting. The default, Point Sample, measures only a single pixel, which could be inaccurate. Either of the other options is a better choice.
- Next, check the Info palette itself (Window: Info), shown in Figure 3.5. Its top half can conveniently be configured to display two colorspaces simultaneously. A separate eyedropper controls each side. The left side should be left at its default, Actual Color, which means that it will read LAB for an LAB file, RGB if RGB, and CMYK if CMYK. Working with LAB numbers is not a walk in the park for the uninitiated, so you should set up the right side to read whichever colorspace you're most comfortable with. That way, you can refer to, say, RGB numbers, even though you're working in LAB.
Figure 3.5 The right half of the Info palette should be set to whichever colorspace you are most familiar with (left). Below, left to right: the palette shows RGB equivalents to the current LAB values; when a curve is being applied, it shows before and after values, separated by a slash; if the value is not reproducible in CMYK, an exclamation point appears after the CMYK numbers to indicate an out-of-gamut color.
You will doubtless think that I should be sent to an asylum for saying this, but after a while the LAB values will start to make more sense than either of the alternatives. I now have my own Info palette set to LAB on the right, no matter what colorspace I'm working in. Even though I've worked in CMYK for a very long time, the LAB values now make more sense to me—certainly more than RGB!
- While on the topic of equivalencies, here's an optional change. In Photoshop, LAB has a fixed meaning: your LAB is the same as mine. Our definitions of RGB and CMYK may not be. Therefore, if we each convert an LAB file to one of the other colorspaces, we'll get different results, unless your workspaces (Edit: Color Settings; Photoshop: Color Settings in certain versions) happen to match mine.
The subject of what definitions to use has generated more heat than its importance merits. It's off-topic for this book, because it has little impact on the question of when to use LAB. However, we have to assume something, and it's going to be what's shown in Figure 3.6. These settings are chosen only because more people use them than anything else, and not because I approve of them, which I do not. If you are dead set and determined to follow the exact numbers shown here, make your settings match; otherwise, leave them alone and you won't miss much.
Figure 3.6 This book uses the above definitions of RGB and CMYK in computing color equivalencies.
If you use these RGB and CMYK settings, your Info palette will report numbers similar to those of this book, although certain other settings may cause them to vary slightly. Otherwise, there will be differences in things like the equivalencies shown in Figure 3.5.
Also, from here on, I'm not going to waste space with a reminder every time the acronyms RGB and CMYK appear that they permit differences in definition. Unless otherwise stated, those acronyms mean the variants thereof specified in Figure 3.6.
- For converting between RGB and LAB, I prefer to use the Image: Mode>Convert to Profile (Photoshops 6–CS), Edit: Convert to Profile (CS2) command, with Use Dither unchecked. Although Convert to Profile can also be used to go into CMYK, I use a simple Image: Mode>CMYK instead.
The reason for dropping the dither is philosophical; I'm not sure it has any realworld impact. By default, when converting between colorspaces, Photoshop introduces a very fine noise, or randomization, hopefully so fine that nobody can see it, yet sufficient to wipe out any banding or posterization, of which phenomena noise is an enemy.
Since we commonly go back and forth between RGB and LAB (and therefore are applying the noise twice), and since there's often a sharpening or contrast enhancement in between that could conceivably aggravate it, I'm a bit leery of putting it in in the first place, although I think it's a healthy thing when going into CMYK. So, I'd use Convert to Profile, but I'd turn off the dither, as shown in Figure 3.7. Also, Relative Colorimetric is the correct Intent setting for most conversions; your system may have Perceptual as the default. In the current state of technology, it won't affect your conversions between RGB and LAB, but you should change it anyway. Once all these fixes are made, they'll be with you until you change them back.
Figure 3.7 The Convert to Profile command permits easy moves back and forth between colorspaces. The highlighted areas should be changed from the defaults.
- If you intend to use any automated adjustment command (Auto Levels, Auto Contrast, or Auto Color, all found under Image: Adjustments) or the eyedropper endpoint tools within the Curves dialog box, you need to reset their defaults, which are pure white and pure black. Instead, as shown in Figure 3.8, double-click the white eyedropper icon in the Curves dialog, and enter new numbers of 97L0A0B. Then, do the same with the black eyedropper, using 6L0A0B. These settings will take effect for every colorspace, not just LAB.
Figure 3.8 The default endpoint settings should be changed to the values shown. To do so, double-click the Set White Point eyedropper (above right) and enter 97 L0A0B in the Color Picker. Then, set the black point to 6 L0A0B (below).
- Finally, a reminder that all curves in this book are shown with darkness to the right of the curve. It doesn't hurt to set it the other way, but you'd have to cope with shapes of the curves that are backwards in comparison to what's shown here. To change the orientation, click once in the gradient bar underneath the curve grid.