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This article is from June 6, 2001, and is no longer current.

Out of Gamut: Color-Correcting Photographs in Photoshop

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I’m often asked, “what’s the easiest way to color-correct images?” My answer is always the same: Fix the neutrals and the rest will follow. True, it isn’t always quite that simple — fixing the neutral areas won’t always solve your color problems. But surprisingly often, if you find something in the image that you know should be neutral — that is, white, black, or gray — and you make it so, you’ll find that the rest of the color falls into place.

In Adobe Photoshop, the tools I always use to accomplish this end are Curves, the Info palette, and a Photoshop working color space. It may seem odd to include the working space as one of the tools, but there’s a very good reason for doing so. Photoshop working spaces are inherently gray-balanced, which simply means that equal numbers of R, G, and B will produce some shade of neutral gray, black, or white. This is very often not the case with monitor or scanner spaces, and it’s pretty much never the case with RGB printer spaces, so creating a neutral in these spaces is much, much harder. (For a more in-depth discussion of working spaces, refer to “Photoshop 6 Gets Smart With Color“.)

Remove the Cast
Let’s look at an example. The image in Figure 1 has some obvious color problems. I’ve never seen a bright blue rock, and I suspect that you haven’t either. In fact, the image overall appears to have a blue cast.


Figure 1: A blue cast detracts from this image.

Even though the cast appears visually obvious, it’s always a good idea to check the numbers in the Info palette to be certain. It can be hard to distinguish between a blue cast and a cyan one, or a green cast and a yellow one, and since the remedies for each are quite different, it’s a good idea to be certain which color is present or absent in excessive amounts.

I use the Info palette to determine pixel values. The Info palette always reads the pixel values of the pixel or pixels beneath the cursor. The exact values that appear depend on two things: the zoom percentage you use to view the image, and the setting for the eyedropper tool. This latter affects the numbers that appear on the Info palette no matter which tool you’re using. I always set it to Point Sample — which takes color data from a specific pixel — rather than 3×3 Average or 5×5 average which grabs the average values of a grid of pixels. The downside of Point sample is that you need to be careful that the pixel you pinpoint is representative of the image — that it isn’t some random scanner noise. The advantage is that you can be very precise, and if you need to sample the average of a group of pixels, you can simply zoom out to a percentage less than 100%. (At 50% view, you’re sampling four image pixels.)

I generally start by looking at the numbers in areas that I think should be neutral. Figure 2 shows the RGB values obtained from two different locations on the rocks in the foreground.

Figure 2: The Info palette displays the pixel values for two different cursor locations.

In this case, the info palette confirms that we have an overall excess of blue. (For further confirmation, I sampled additional areas — the snow and background, for example — and all showed a predominance of blue.)


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Bruce Angus Fraser (9 January 1954 – 16 December 2006) was an author who specialized in digital color technology, including hardware and software for creating and managing color images and publications. He co-authored "Real World Photoshop" and others. He was a founding member of PixelGenius, LLC.
  • anonymous says:

    Great source of useful info, would like to see more articles like these.

  • anonymous says:

    This article is a great read for anyone who finds themselves color correcting images.

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