Photoshop color correction

When you correct or enhance an image in Photoshop, do you head first to Auto Levels or Brightness/Contrast? Do you select the parts you think need to be fixed, and then Levels them or Color Balance them?

I used to do these things. But I have begun to see the light, thanks to a book I checked out from the library: Professional Photoshop: The Classic Guide to Color Correction, by Dan Margulis. Little did I know that there would ever be a reason for me to bother with CMYK or LAB color profiles . . . I thought that for everyday schmoes like me, RGB was everything I needed. Not so. LAB color is particularly good at bringing out greens and reds in things like plants and stones.

I took this photo at Hampton Court Palace (near London) in 2005. It was beautiful in person, but in the picture the whole scene looks grey, and the clouds are blasted almost to white:
Hampton Court, rear view Hampton Court, rear view (color corrected)
(click for larger versions)

Even in these thumbnails you can see the color and detail difference between the before (left) and after (right) versions. The adjustment was done by first converting the image to LAB color space, and then tweaking the curves on the A and B channels. Altogether, there are two main layers of Curves adjustments: one for the whole scene (involving the AB channels) and another applied to a gradient mask, more or less isolating the sky, which was adjusted with the L channel. View them large to savor the full effect. The trees become green, the stone becomes warm, and the sky fills out very pleasingly, to my way of thinking.

I’m not at all suggesting that this picture couldn’t be better yet . . . but this huge improvement cost me very little time and effort in learning how to use Curves. Here’s another example, again from Hampton Court (Left: before; Right: after):

Hampton Court Hampton Court (color corrected)
(click for larger versions)


This one was done in RGB. I selected a white point and a black point, and then simply typed numbers into the curves dialog box for the Red, Green, and Blue channels individually. This is an image of the altered RGB curves. Notice that each one is adjusted a little differently—that’s one of the cardinal rules of using Curves, according to Margulis (and obvious to those who have used the methods he describes): never adjust the Master Curve. Always adjust each channel independently of the others. The payoff is a photo that looks awesome. And I only had to read through chapter 3! I’m reading the whole book, though, and expect my photos to look consistently excellent as a result.

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