Adobe Photoshop CS3 Tutorials
Color Correction / Histogram
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Subtitles of the Movie (Adobe Photoshop CS3 / Color Correction / Histogram)
Let's take a look at a tool that is quite useful and will help you to evaluate the tonal qualities in your image. From shadows, highlights and also the midtones and it's called the histogram. I'm gonna go to the image menu, I'm gonna choose adjustments and then I'm going to choose levels. When this dialog box appears we're presented with this mountain range type graph and this is the histogram. It shows you the distribution of pixels that are in the white area, the midtones as well as the dark area. As we see here we can work in channels and in this case we have a black and white image so we only have grey available. And we also have these sliders here. These sliders represent the pixels that are gonna be black, the pixels that are gonna be white or clipped to white and our gamma slider. We also have our output slider as well as some other options such as the eyedroppers. Now let's go ahead and look at this image, based on this image the histogram tells us that we have a lot of pixels in the midtones, we don't really have that many pixels in black and we don't have that many pixels that are white. So what we can do is we can use the sliders to determine the starting point for pixels that are gonna be black. So when we move this slider here what we are really saying is that the black starts here and anything that's to the left of this slider is gonna be completely black. So if I go ahead and continue moving this slider over you'll notice that everything that was in the midtones I'm pushing to black because once again everything that's past this slider to the left is gonna go toward black. So if I go all the way look what happens, I'm pushing everything toward the black. Don't forget this controls black so I'm gonna move this back over and do the same thing on this side. Whatever is on the right of this guy is gonna go toward white. And this is gonna control our midtones or our gamma so we can adjust that as well by using this left and right. Now the values here that you are looking at go from zero to 255 and once again zero represents black 255 represents the white tones. And the one is an exponent that gives us an ability to work in a power of something. So 1 power, 2 power, 3 power, that kind of thing, like you know E equals MC square that kind of thing, that little exponent thing. So let's go ahead now and use these eyedroppers. What the eyedroppers allow you to do and by the way whenever you want to reset you don't have to click cancel and start over just hold down the alt or option key until you see the word reset here and click one time and now everything is back to the way it used to be. What we can do with the eyedroppers is we can click on the eyedropper to set a black point so we look at the image and determine where the blackest point is on the image. And I'm gonna just click right here in the jacket and as you see here the histogram adjusts automatically. Likewise I can do the same thing with the white eyedropper and determine that the short collar or part of his skin is the white point. And once again it adjusts itself accordingly and we can then use the gamma slider to change the image to increase or decrease the midtones. So this is what the histogram palette will do for you. It will help you to determine the lightest and darkest pixels as well as to look at the entire range of your pixels and determine which parts are gonna be black, white and which parts are gonna be in the gamma range. And you can use these sliders and just as a little hint usually want to stay in the mountain range so if you have like nothing here and your pixels start here try to put the slider at the very base of the mountain range like so and then adjust it from there. That's just how I use it and it helps me to figure out exactly the best way to get the best contrast in a black and white image or an image that's washed out too much.
Tutorial Information
| Course: | Adobe Photoshop CS3 |
| Author: | Dwayne Ferguson |
| SKU: | 33782 |
| ISBN: | 1-933736-98-4 |
| Release Date: | 2007-08-02 |
| Duration: | 9 hrs / 161 lessons |
| Work Files: |
Yes |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |
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