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Any time you edit an image, you’re almost certainly going to need to adjust the overall brightness and contrast. It’s one of the most fundamental edits you can make in Photoshop. It’s incredibly rare that an image will come straight out of the camera looking great with perfectly exposed shadows and highlights.
Like with everything in Photoshop, there are a few different ways you can do it. In this article, I’m going to look at a couple of the best options and explain how to use them.
Brightness, Contrast, and the Histogram
Before diving in, let’s take a moment to consider what brightness, contrast and a couple of other terms actually mean when it comes to digital images.
The brightness, or more properly the luminance, of every pixel has a value of between 0 and 255 where 0 is black and 255 is white. The relationship between the pixels determines how bright the whole image appears, how much contrast it has, and whether there is detail in the shadows and highlights.
If the image has large areas of high luminance pixels, the whole thing will look bright. Conversely, large areas of low luminance pixels mean it will look dark. If there is a big difference between the brightest and darkest groups of pixels, it’s going to have a lot of contrast, vice versa and it’s low contrast.
When you look at a histogram, this is the information you’re getting. A histogram is a graph with the luminance values on the x-axis and the proportion of them on the y-axis. If there are lots of pixels with a luminance of 50, there will be a big spike on the graph. If there’s only a few or even none, it’ll be a small spike.
There is nothing inherently wrong with any kind of image. It all depends on what emotions you’re trying to evoke. No one wants dark gloomy wedding photos. When you’re editing brightness and contrast you’re just trying to fine tune the image either to make it more accurate or to better represent the mood you want.
For this article, I’m going to look at four different adjustment layers: Brightness/Contrast, Levels, Curves, and Exposure. They’re the first four options in the Adjustment Layer panel. They each offer different levels of control.
There are other ways to adjust brightness and contrast in Photoshop, but adjustment layers are the best way to do it. Anything else is either incredibly time-consuming or destructive.
When you’re working with brightness modifying adjustment layers, you should set the layer blend mode to Luminosity. That way there aren’t any unintended color shifts.
Brightness/Contrast Adjustment Layer
A Brightness/Contrast adjustment layer is the simplest option and, for that reason, should only be used when you are making edits that don’t need much fine tuning.
There’s a Brightness slider, a Contrast slider, an Auto button, and a Use Legacy check box. That’s it.
The Brightness slider adjusts the overall luminance level of the image. Dragging it to the right will increase the brightness of the highlights and midtones while leaving the shadows relatively unchanged. Dragging it to the left has the opposite effect, darkening the shadows and midtones but leaving the highlights alone.
The Contrast slider adjusts contrast in a very blunt way. Dragging it to the right brightens highlights and darkens shadows while dragging it to the left brightens shadows and darkens highlights.
The Auto button is the most useful thing about Brightness/Contrast adjustment layers. Photoshop makes a best guess attempt at adjusting the image. When you’re batch processing images and don’t need to be particularly accurate, this can be really useful.
The Use Legacy checkbox should never be touched. It makes Photoshop use a much worse adjustment algorithm from pre-CS3. There’s a reason things have changed.
Levels Adjustment Layer
The Levels adjustment layer, along with Curves, are the main ways you’ll adjust brightness and contrasts. Levels is a little easier to use but Curves offers more fine tuning.
With Levels, you control the Black Point, Gray Point, and White Point. They’re the little sliders circled in the image below. With these you can modify the histogram.
Let’s say you drag the Black Point slider to the right from luminance 0 to 10. Now any pixels that originally had a luminance value of between 0 and 10 will be rendered as 0. All the other values between 10 and 255 will also be shifted slightly to the left.
The Gray Point and White Point sliders do the exact same for the midpoint (luminance level 128) and the highlight level respectively.
With Levels, the simplest way to brighten the image is to drag the White Point left, to darken the image is to drag the Black Point right, and to add or remove contrast to the image is to play with the Gray Point.
When it comes to brightness and contrast, you can ignore the Output sliders.
Curves Adjustment Layer
A Curves adjustment layer is the most powerful way of modifying an image’s brightness and contrast; you’re directly manipulating the histogram.
Rather than three point sliders, Curves has a single sloped line running directly through the histogram. This represents the input values. If you click on the line you create a new point, so for example, you can create points at luminance values of 25, 50, 193, and 215. Rather than just having three handles, you have 256 potential handles.
To brighten all the tones around a selected point, you drag it up. To darken all the tones, you drag it down. The shape of the slope alters dynamically so as to minimize any weird effects.
The best way to learn to use Curves is just to play around with them. The basics are:
- If you want to brighten an image, make a point somewhere in the middle and drag it up. Do the opposite to darken.
- If you want to add contrast, create a point in the shadows and drag it down and a point in the highlights and drag it up.
For most images you edit, you should use a Curves adjustment layer to edit brightness and contrast.
Exposure Adjustment Layer
The Exposure adjustment layer is a little different. Even though it sounds like it should be perfect for modifying an image’s exposure (it’s in the name!) it’s actually a poor tool for the job. What Exposure is for is expanding the dynamic range of HDR images.
If you’re looking to brighten or add contrast to a regular image, don’t use it.
You should adjust the brightness and contrast of every image you take, even if it’s only a tiny amount. It’s unlikely the photo came out of the camera looking perfect!
In this article, I’ve looked at a few ways to do it with adjustment layers. The two you should use 99% of the time are Layers and Curves. If you’ve any questions about brightening or adding contrast to an image in Photoshop, ask away in the comments below.