In Focus Vol. 2 No. 1

Q: LAB mode… What is it good for?

A: This often overlooked and underused color mode in Adobe Photoshop has long received the undeserved scary mode reputation among beginning and intermediate users. It’s about as welcome as going for a long walk through a dark forest to get to your exploratory surgery appointment.

First of all, you should know that it’s the only color mode in Adobe Photoshop that can actually separate color from brightness and contrast, which to a photographer is an untapped source of what could be called magic.

Sure, you could get somewhat close to the same results using RGB or CMYK, but no matter what you are trying to do, it will undoubtedly take you many more steps to achieve it in those modes.

For starters, let’s address something the LAB mode is good for: sharpening and blurring. This is an excellent method, particularly if you over-compressed a file in the jpeg process.

Many of you face the challenge of digital aberration when the edges of two different colors meet and a fringing appears. You can try to control it using Photoshop’s Camera Raw plug-in, but I think you will much prefer the results in LAB.

To do this, first switch your image to LAB mode (see Step 1). You won’t damage your file by doing this. Go to the A channel (Mac command+2, Windows Control+2), and then go to Filter>Gausian Blur. Results should vary on your image, but try a range of 2.0-8.0 pixels (surface blur works well for CS2 users).

Next, go to the B channel (Mac command+3, Windows Control+3). Repeat the blur but make sure you choose a different pixel value than what you used on the A channel. Now view your before-and-after results using your history state palette.

At this point, if you have further retouching or toning to do go ahead and switch back to the mode you were in previously, which for most users is RGB. When the image is done and sized and all that is left to do is the sharpening you’ll want to return to LAB mode and follow the next steps for sharpening.

Now go to the lightness channel (Mac command+1, Windows Control+1… see Step 2). Go to Filter>Sharpen>Unsharp Mask. Play with this to learn what the possibilities are. A useful formula I learned from Dan Margulis’ book, Photoshop LAB Color, is to keep the radius between 7 and 20 pixels and keep the amount under 100. To view your results go to the composite channel (Mac command+ ~, Windows Control+ ~).

Remember to convert back to your native color mode when you’re finished, as most processing centers or graphics programs will not recognize the LAB color mode. Expect amazing results in minutes.

Kim Herrera is the color management expert for Logan Photography at Studio Exchange, Santa Ana, Calif., and runs KCH Digital, a digital artistry, education, and consultancy firm.