Adobe Photoshop Image Restoration Tutorials
Basics / Curves/Digital Cameras
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Subtitles of the Movie (Adobe Photoshop Image Restoration / Basics / Curves/Digital Cameras)
I want to show you a color correction right now that is quite common in digital imagery and that is white balance correction, and here is how to make that correction in Photoshop. We do that most effectively using the curves dialog box. So what we are going to do is first of all we are going to analyze the information palette as it pertains to the RGB values in this image, and the way we do that is we click on the information tab and then run your cursor over the image and look at the values that result. And I want to run this cursor over different areas of the image for just a minute here and I want you to watch these values, watch the values as they change, right up here and I want you to get a feel for how those values balance and how they relate to each other. Let's just take a minute, look at those numbers and see if you can come up with a consensus on what the relationships are, and what you notice is the blue values are lower than the green and the red. The red values are much higher than the green; we need to get those in balance. In other words for a properly adjusted white balance, the RGB should be pretty even. There is no specific number that it needs to hit; it is just whatever number it is, needs to be very similar to each other. So the way to achieve that most effectively is with the curves dialog box. So let us open that now and let us take a look now as we run our cursor over the image, we see that there are very low blue values. So we need to boost the blue channel and we see an immediate improvement in that image, but it is still off. We can see that by looking at it, actually I took the blues maybe a little bit too high; bring those down just a bit, go back and look, and the numbers in the left are the old values and the numbers on the right are the new values. And of course now the red and the green are going to be exactly the same, because we have not adjusted those yet, but the blue value you can see has changed considerably, it is a lot higher after the adjustment, and a lot closer to the green and we are going to kind of adjust for the green. Don't ask me why, it is just kind of an arbitrary decision I have made on this particular image. Okay, so now the reds are still higher, so let us adjust the red, let's take ourselves to the red channel and pull it down, because it is too high, so we want to reduce it, look at that. A lot closer together, these values on the right are much closer than the values on the left were to each other. That red still needs to come down some more, you can see the red, see how those numbers on the right are much closer together. They do not have to be dead on exactly the same, but just closer together. The red value is lower on the right than it is on the left, the blue value is higher. That is an image that is more balanced, closer to where it needs to be and again, does not have to be exact but you can continue to tweak it. Let me go under image, but that looks a lot better and I want to show you the before and after. So it's very dramatic, there is before and there is after, looks a lot better. It looks a lot like it does when you go into the grocery store. Now while I have you here, I want to point out something to you that you should be aware of when using digital cameras and that is video noise. And the noise in a digital camera is inescapable the higher the ISO setting you use, this was shot with a sixteen hundred ISO setting and again I did that on purpose so that I could show you video noise. The way that digital cameras achieve the higher or the faster ISO settings is that they simply boost the video signal and whenever you boost, the video signal, inescapably, you also boost the noise, so the higher the ISO setting, the greater the noise situation. And here it is almost intolerable, we have got to this modeled color, very modeled, very un-smooth, should be very smooth. This is a very contiguous color right there and it's just all modeled, that is video noise. Let's take it down to this box, you see that, it is really pronounced here. Up here the red; this does not look contiguous, not smooth color gradation, watch those higher ISO settings because the higher you go, the more noise you are going to have. You cannot correct the noise situation, unfortunately, very easily; I have never found a really effective process for correcting noise. It is just one of those things you have got to live with, so try to shoot your digital images that are on a hundred or two hundred ISO settings and you will keep your noise levels to a minimum, but if you need to shoot at a sixteen hundred, make sure that to the extent you can you have a nice busy image, at least your exposure is properly exposed, with a lot of contrast and a lot of color saturation, that is to keep the noise levels, the perceptive noise levels, at an absolute minimum.
Tutorial Information
| Course: | Adobe Photoshop Image Restoration |
| Author: | Phil Hawkins |
| SKU: | 33473 |
| ISBN: | 1932072705 |
| Release Date: | 2004-01-27 |
| Duration: | 4.5 hrs / 77 lessons |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |
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