The primary power of the equalization adjustment is to take the colors inherent in the two color channels—A and B—and run them to the maximum. This means that, for example, reds become redder and blues become bluer. This can be useful for fixing skies and adding saturation among other enhancements; however, the limits to suspension of disbelief of the Lab palette can become apparent, so opacity should generally be set low for an A- or B-channel equalization.
- [Instructor] Equalization is an important adjustment in the context of LAB Color in Photoshop. With LAB's color opponent channels, to equalize doesn't behave the way you would intuitively expect it to from its name. In fact, it does something like the opposite of the common English meaning of equalizing. It takes colors toward their maximum inherent value. Reds get redder. Blues get bluer. Greens get greener and so on. On another front, equalizing the L channel means that whites get brighter and blacks get darker. In other words, contrast is increased. There are three significant channel equalizations in LAB Color. Let's take a look at each of them in the context of this iPhone shot of the soaring ceiling of the Chiesa di San Giuseppe dei Padri Teatini in downtown Palermo, Sicily. This is a very baroque Sicilian church and has plenty of colors to go around so it makes a good showcase for the LAB equalizations. With the image in LAB Color, Image, Mode, LAB Color, to equalize the L lightness channel and the channel's palette, select the lightness channel. Next, make sure all three channels are selected by clicking the eyeball to the left of LAB. Choose Image, Adjustments, Equalize. Note that the dark areas in the baroque ceiling are darker and the white areas are whiter. That's what an L channel equalization does. This is probably a good time to point out that I'm not demonstrating an LAB all channel equalization because the impact of an LAB equalization is exactly the same as equalizing just the L channel. To see the next equalization, use the History panel to undo the equalization that I just did and select the A channel, again making sure that all channels are visible in the channels panel, and go Image, Adjustment, Equalize. By the way, sometimes I have a little problem finding the equalize adjustment on the Adjustments menu. It's way at the bottom. You'll observe that with the A channel equalized, black and whites are gone and greens and reds or magentas are far more pronounced. All right, back up again one more time and let's fly with the B channel. So Image, Adjustment, Equalize. Now any area where there was even a trace of blue is more blue and the areas where was even a trace of yellow are more yellow and areas like the windows where there was no visible blue at all because there was light coming through now have a trace of blue. Do remember that to use the results of your adjustment, you must make sure that all three channels have been reselected like this and that your image is converted back to RGB. You can use the striking adjustments as a bold color palette. You'll see that the trick is to use the colors that the equalizations enhance in moderation so you don't go overboard and get all baroque on your images. Or as Oscar Wilde put it, everything in moderation even moderation.
- Converting images to Lab Color space
- Applying Curves to Lab channels
- Selective sharpening
- Inverting channels
- Making per-channel equalizations
- Using the Lab action
- Combining Lab Color with blending modes
- Making patterns with Lab images