One of the more common problems you'll run into when working with digital images is they tend to sometimes be flat. They don't have a lot of contrast and here's an example in this image. It's great composition and nice color, so forth, but it's just looking a little flat. It needs to be a little bit pumped up and have stronger blacks and stronger whites. Now there is a variety of different tools in Photoshop and features that let you address this problem. I am going to teach you about Levels, and specifically, the Levels Adjustment layer. Now before we do that, I've got a layer here called 256 Levels. I am going to go ahead and turn that on, and it's just a gradient from left to right where it goes from black to white.
What this represents is the number of tones or grayscale values there are per channel in an RGB image. It turns out that an RGB image is actually made up of three channels of light: red light, green light and blue light. In fact, if I go ahead and turn off the 256 Levels layer so I can just see my color image again, and I'll go to the Channels panel inside Photoshop here, iff we take a look at just the Red Channel by clicking on the word Red, you'll see it's a grayscale image where each color value is mapped to a grayscale value.
So, the brighter the color, the lighter the grayscale value, So, where there's going to be a lot of red in the Red Channel, that red color would be represented by a light pixel. If it doesn't have a lot of red, then it will be dark. So, if you can take a look at the blue strap here or the blue with their shirt, those pixels end up being dark because there is not a lot of red in them. Likewise, if I click on the Green Channel, you will see parts of the image that have green in them will be brighter. The parts of the image that don't have green in them will be darker, and the same thing for the Blue Channel when you click on Blue.
So, when you break down a color image into three individual channels of light and think about each of those channels being represented by a grayscale image, how many different levels of gray are there per channel? It's 256. 0 is black, 255 is white, and then every gray value in between is assigned as specific number between that range. Let's go back to the RGB Channel, so I see all the composite red, green, blue channels together and see my color image. We'll go back to our friend the Layers panel. I know the Channels panel can be a little scary for folks.
Let's go back over to layers, and we'll turn on that 256 Levels layer again. What I want to teach you here is what happens when you start adjusting the levels with the Levels Adjustment layer. Let's go ahead and do that. Go to the Adjustments panel. I am going to click on the icon for Levels to bring up that editor. Now there are three knobs, or dials, that you can play with in the Levels histogram here. Now if you take a look at this chart, this nerdy word histogram, that is a chart of the tonal values in your image, how many pixels per tone.
So, if you look at the Black slider, that represents tonal value 0. If you look at the White slider, that represents tonal value 255. And then your middle slider is your 50% gray point, your middle point. And this slider will adjust automatically, based on where you move the white and black sliders. It's always going to try to find the absolute middle between black and white if you don't touch it. You can always override it and move it yourself. But if I start dragging the White slider, you'll see that Gray slider moves with it to always find the new mathematical center of the range of tones.
So, what's happened when you actually move the sliders? Okay. I am going to turn on some Guides to help us out here. I'm going to go to my View menu and Show > Guides. What I have done is I've actually drawn out some Guides, which will be useful in a moment. I am going to switch to my Eye Dropper tool. I am going to press the letter I. I am going to bring up my Info panel under the Window menu, Window > Info. And as I move the Eyedropper around my screen, you'll see some numbers in the RGB section of the Info panel, and they are split in half because it's showing you a before and an after value.
Right now, since I haven't done anything in the Levels panel, they are still at the default values here. I'm just seeing the same numbers for both R, G and B on the before and after side of that split. If I put my cursor all the way over to the left, you'll see that that's tonal value 0, so that's absolute black. Those pixels on the very left edge there are 100% black, or tonal value 0. If I move the cursor all the way over to the right, you can see the tonal value is 255, so absolute white. And if I actually got out rulers and found out my precise middle of this particular image, in terms of pixel dimensions, I would find 128 as my midpoint gray, and there it is, right about there.
So, back to what happens when you actually start adjusting the Level sliders. I am going to take this Black slider and drag it all the way over to 20. Now what I am telling Photoshop to do is, "Hey, Photoshop. Every pixel in this image that has a tonal value of 0 to 20, I want them all to become 0." So, now to kind of prove this to you, if I move my mouse anywhere over here to the left of this guide, you'll see on the right side on the Info panel, so take a look at the left numbers and the right numbers, the left numbers are were we started, the right numbers are where we're going after doing this adjustment in the Levels Adjustment layer.
If I move my mouse anywhere between the edge of the image and that blue guide, you can see all those tonal values have now been re-mapped to absolute black. They've all become zero, in terms of tonal value. The new midpoint is going to be somewhere else than the actual precise middle of the image, because we've shifted all those grayscale values over proportionally, as I adjust that Black slider. So, same thing with the White slider. If I move that to the left - to say 224, sounds good - as I move my mouse in the area to the right of this blue guide, you'll see that all those pixels have now been mapped to white, or 255.
And again, that middle triangle, the grayscale triangle, moved in proportion with that White slider. So, really, what you're doing is you're setting a stronger black and a stronger white. And you are going to be clipping detail in the process, and we'll cover that in just a moment, but you are shifting a certain range of pixels to go absolute black and a certain range of tonal pixels to go absolute white and then your grayscale value changes in between. Let's go ahead and reset this adjustment layer. There is a click of a button here at the bottom where it says Reset to adjustment defaults, so it's like nothing has happened.
I'm going to go ahead and turn off that 256 Levels layer because that was just for visual purposes, and I'll go ahead and close the Info panel. So, it's not distracting, we'll turn off the Guides as well, View > Show > Guides. All right. So, we've got our original color image again. You can see the histogram is now reflecting the chart of the tonal values of the color image instead of having that grayscale layer turned on. It's just showing you the histogram of the layer stack as it's currently seen with the layers turned on or off. So, here when you take a look at this histogram, it actually tells you quite a bit of information.
It's telling you there are gaps, there are missing tones in this image. You can see there isn't actually a pure 100% white set of pixels, because there's no piles of pixels represented in that part of the graph. There is also not an absolute black set of tones in the image, because there is no stack of pixels in the black area as well. So, the way you work with Levels is you simply move the sliders to where the piles of pixels begin in the chart. If I move that Black slider to the right, right about level 5 here, that's where there are some pixels that have that tonal value.
There is not a lot of them, but there are a few. The image actually already starts to look a little bit better. I'll turn it on and off. Here is before, and there's after. And that's very subtle, but you did see a shift. Not very many pixels became 0s because there weren't a lot of pixels in that range anyway, but remember that middle slider moved with the Black slider. So, it's actually remapping the midtones and making them darker as you slide that over to the right, meaning you're increasing contrast in that range of pixels. I am going to go ahead and move that slider all the way over to level 15.
Now I have told Photoshop, "Every tonal value from 0 to 15, you are now going to go to 0." Now are you losing detail in the shadows? Yes, absolutely. But are you losing much detail in this particular image? No, because there weren't a lot of pixels that had that tonal range in them anyway. Let's move that White slider over to the left, and we'll take this down to say 195, okay, right there. Now, here I am starting to lose a little bit of detail on the right side of her face, and I can kind of just see that really quickly, visually here.
But if you really want to be sure where you should start moving the slider to, a good rule of thumb is always to start where the actual piles of pixels begin in the chart, kind of right there. So, it turns out that's about 218 in this particular image. And then if you want to increase the contrast even more, it's helpful to see where you are going to be clipping detail in those highlights as you drag the slider. So, here's a little power tip for you: hold down the Option key, or Alt key on Windows, and when you drag the White slider or the Black slider, it gives you what's called a Clipping Preview.
As I move that slider left or right, you'll see, on the screen, where certain pixels are going to be blowing out to absolute 255, or white in our analogy here. As you can see in the side of that face, if I go over to 189, or 187, or whatever, you can see I am really starting to clip a lot of detail on the highlight side of their face. So, with the Option key held down, or the Alt key held down, I can just keep dragging that White slider left or right until I'm satisfied with getting as much boost in contrast in the highlights as possible but deciding where I don't want to clip detail anymore.
So, I am going to take this particular image, let's say, 210. And that looks about good. I'm not losing much detail, but I've increased the overall brightness and contrast of the image. Here is our before. We can click on the eye at the bottom of the Adjustments panel to see the before. Here's after, and you can see I've made that image have much more visual pop. I've got great contrast. I've established a true black and a true white and adjusted the overall tone quality of the image. And the best part, because it's an Adjustment layer, it's nondestructive. I can turn the whole layer on and off.
I can lower its Opacity, if the effect is too strong I can lower it, and I can even mask it off if needed. So, there you have it. I hopefully have taught you not just about the Levels Adjustment layer but how Levels actually work, and you can apply that to any image that has a little bit of flat no contrast issue. Move the Black slider in. Move the White slider in to where the piles of tiles, or piles of pixels begin. If you want to take it even further, hold down that Option or Alt key as you drag those sliders so you can actually see where detail is going to be clipped in the process.
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