Adjusting tones with Levels
Adjusting tones with Levels
Almost every image can benefit from a Levels adjustment. When you adjust levels, you're remapping the darkest tones in an image to pure black, and the brightest tones to pure white. That causes all the gray tones in between to be stretched out across the range between the whites and the blacks. The result is an image with more contrast between darks and lights, and a wide distribution of gray tones in between, which usually makes a photo look better. Now, adjusting levels often does impact the colors in an image, but in this movie, I'm not focusing on adjusting color. Rather I am looking at adjusting tones in a color image.
To get a sense of what tones are, if you're not already sure, try this "high-tech" technique. Squint your eyes and focus on the photograph you see here and try to see just the dark, light and gray shading, rather than the color. Those are the tones that I am talking about in this movie. As with all of the image adjustments that I am covering, I strongly recommend that you apply Levels as an adjustment layer rather than as a direct adjustment. Because as you know from other movies an adjustment layer is non-destructive of the image pixels and it can always be re-edited.
In Photoshop CS4, you can create a Levels adjustment layer not only from the Layer menu at the top of the screen up here, as you always have been able to, but and this is the new piece, from the Adjustments panel. If your Adjustments panel isn't open, then you can open it from the Window menu at the top of the screen and when you're ready to create a new Levels adjustment layer, you will go this second icon right here and click. That causes two things to happen. Down in the Layers panel, you can see the new Levels adjustment layer floating above the background photo layer, and in the Adjustments panel you see all of the controls for Levels.
Notice that there is a histogram inside the Levels Adjustment panel, and it looks just like the histogram up here in the Histogram panel. In fact they are the same. But the reason I like to have the Histogram panel open also is that the histogram in the Levels Adjustments panel doesn't update as I make changes to it, like the Histogram panel does. So I use the Histogram panel to check my work as I'm doing it in the Levels Adjustments panel. The Levels histogram just like the one in the Histogram panel is a bar chart of the 256 potential grayscale values that an 8-bit image can have.
In the Levels panel, you actually can see those tones represented here in this gradient. If you could push this gradient up underneath the chart, it would be even easier to see that the far left of the chart represents the blackest blacks, the far right of the chart represents whitest whites, and in between are all the gray values. The black mound in the middle represents the actual tones in this open image. It's not really a mound. It's a collection of vertical bars, squeezed up next to one another.
Each bar represents the prevalence of a particular shade of gray in this image. The tall bars here mean that there is a relatively large amount of that particular shade of gray, which would be represented here on the bar chart. The short bars, like those over here, mean that there is very little of that particular shade in his image. So in this case, there are very little dark shades and almost no white shades, except for maybe those represented by the short spike, which I believe are the specular highlights right here.
These we really don't care about when we're doing a Levels adjustment because by nature, they are always pure white. My goal when adjusting levels in his image is to take that mound and stretch it out, so it reaches further across this bar chart and also to make sure that there are some white whites and some black blacks, and that there is detail in the light and dark areas at either end of the tonal curve. So to adjust the levels, all I have to do is come into the Adjustments panel and take this white slider here and drag it in toward the left until it just touches these short bars.
What that does is take any pixels that are to the right of that slider and push them to pure white with no detail. So that's why I don't want to go too far into this mound, because if I do, I am taking all the pixels represented by the bars to the right of this and making them pure white, so that there isn't enough detail in the image. I am going to pull that slider back to the right. Because the question is, well, how far in should I go? And the way that I can tell is by holding down the Option key on my Mac, or the Alt key on the PC, as I drag that slider in, and looking for little patches of color.
There I can see a little bit of red color there and that represents some pixels that are starting to go pure white. The bright white pixels at the bottom- right corner are the ones that represent the specular highlights, and I am not really worried about those going white. Now I am going to go over to the other side of the chart and grab the black slider, and I am going to hold down my Option key again, and drag to the right so I can see where to stop with that slider. I also want to put this one just under the mound of pixels. Now, you can see a big blue patch on the left that is pure blue.
Those are pixels that are pure black and they came in like that from the digital camera. They are represented by the black spike on the far left of the chart. I am just going to let those stay pure black, because I think it fits in fine with the design, and I am more interested in these other blue pixels. So when I just see a few of those, I release my mouse and that's my initial Levels adjustment. The other thing I want to do is come to the gray slider in the middle and drag that to the right to darken the entire image, and that happens without disturbing the new Black & White points which I just set.
Now, if you look in the histogram above, you will see that that the mound has spread out so that you can see gaps in between the vertical bars. This is because the tones in the image have now been spread out across the entire tonal range, which is what I wanted, and I think the image looks better. Sometimes it's hard to see small differences in brightness and contrast. So at this point, I will go down to the bottom of the Adjustments panel and I will click this Preview icon right here, holding it so I can see how the image looked when I started. It had this kind of gray dull film over it, as compared to now, when it pops with contrast and brightness.
Because I made this adjustment as an adjustment layer, I can come in and change it at any time. So if I were working on another layer, like this background layer, and I wanted to come in and tweak the Levels adjustment, I could just click on the Levels 1 adjustment layer and come back in and move those sliders wherever I wanted them to be. And I can do that at any time, even after I save and close the image and reopen it. A couple of more things to show you here. There are presets for Levels. They are located back in the Adjustments panel or here in the Custom menu at the top of the screen.
So you can try those out if you want as opposed to creating a custom Levels adjustment as I just showed you how to do, and there is also an Auto button here. I avoid the Auto button. In the Levels Adjustment panel, the Auto button sometimes results in a colorcast, because it adjusts each color channel individually. So for example, if I click Auto here, you can see a faint magenta cast in the image. So I will press undo. That's Command+Z on a Mac, Ctrl+Z on a PC to go back to my good Levels adjustment.
That's the basic technique for adding contrast and brightness to an image with Levels. You've given the image some true black and white tones and stretched out the gray tones in between, eliminating the dull look that was caused by a lack of optimum contrast. Sure, there's more you could do to the image now. You might add a Hue/Saturation adjustment layer or some color adjustments, but you certainly have improved the basic tonal structure of the image by applying Levels.
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