Join Taz Tally for an in-depth discussion in this video Evaluating the image, part of Photoshop Color Correction: Target-Based Corrections.
In this project, we're going to take the fundamental concepts tools and techniques that we learned in the color fundamentals course. And using histograms to help us neutralize images, neutralize grayscale, really to the next level. And if you haven't seen that color fundamentals course, and learned the details about how you can use histograms to neutralize an image, I'd really recommend that you watch that course. Just to review the basic concept we've been working with, is if you have portions in your image that are supposed to be neutral that is grey, if you make them neutral and grey, then the color in the rest of the image should be correct.
And all of this goes all the way back to our discussion of, all color is controlled by grayscale. Well, when we look at this image, we can see no matter what your monitor's like, that there is a very strong color cast in this image. And we can tell that just by looking at this grayscale target. This is a ten step grayscale target, that I actually have designed and I produced. And it's made specifically for doing these kinds of corrections. Everything about this target is gray. Right? Even this background. But each of these swatches, there's ten swatches here, and each of these there's is supposed to be neutral gray.
And you can tell just visually just looking at this image, that this is not a neutral gray target. So this target was placed in the image, and then the whole thing was captured with a camera, so that the same color cast you have on the fabric, you also have on your grayscale target and vice versa. So our concept is if we get the target neutral gray, if it's correct, if we correct this image based on the target, then all the color in the image should be correct. Alright, so we can see that this is a fairly complex color cast here. And to complete our image evaluation, let's look over here at our histogram as we always do.
When we look at the master histogram, in just the distribution of tonal values we see. You know, there's a pretty good distribution of data, when you consider all three channels combined together, is a little bit of a flat area here on the highlight end of the master. And then, there's actually a little peak, a little bit of loss of data on the shadow end. I'm not sure which channels those come from. But when we look at the individual channels, and or, let's just go ahead and switch this to colors so we can see the imposition of all three channels across each other. We see that there's a strong offset of the red to the right, in relationship to the green, which in turn is offset to the right of the blue.
When we compare similar areas in the histograms, for instance, this tall peak that we see here, notice how it's offset significantly, not only as a highlight but these tall peak has offset. So we really do have a fairly strong color cast here. Now remember, we're not going to just base our correction based upon the whole image, we're going to do the target. So what we're going to do is, we're going to come in here, and let's just grab the Polygonal Selection tool. And we're going to just select the ten step targets here. And what we're monitoring then, based upon our histogram, is actually the data just on the ten step grayscale target.
And sure enough, we see that the red is offset from the green is offset from the blue, and by the way, each of these peaks that you see here, represents one of the ten swatches on the grayscale target. So we have one, two, three, four, five, six, seven, eight, nine, ten. And the same thing goes for the other two channels. Notice we've got two grayscale target swatches that are pretty close to each other here on the highlight end, and those are going to important for us. But the other thing that we see here, so we can see there's some definite offset. But if we look at the space between the various swatches.
Like, in the red channel and the green channel and the blue channel. They're very different as we move across the tonal range. Notice they're fairly close on the red channel, a little bit wider on the green channel in the highlight, and much wider on the shadow. Alright? And the blue here are much tighter together in the shadow portion than the green, which in terms is quite a bit tighter than on the red. What that means to us is that we don't just have one consistent color cast across this entire image. Is that we have actually a shifting color balance, all the way across the tonal range. So, that's going to create some problems.
And we're going to see how important the target is going to be here, to helping us correct and adjust a complex color cast.