How to Use the Photoshop Levels Adjustment
Whilst this tutorial’s titled How to use the Photoshop Levels Adjustment, you can apply it to many other editing tools. In fact, when you watch the video, you’ll find it demonstrates the Levels adjustment in Capture One and Affinity Photo, as well as Photoshop. That’s because the Levels adjustment is a common tool shared by many photo editors. Once you learn how to use Levels in Photoshop, you can transfer that knowledge to other editing software. That’s what this and other tutorials in the series are about.
Understanding Image Tones
But before you can understand the Levels adjustment, you first need to understand image tones in photo editing.
When we talk about tones in an image, we are ignoring colour and talking about how light or dark each pixel is. To represent this brightness, we use a system of numbers. In Photoshop, the tones in our image can range from a value of 0 to a value of 255. What an image tone has a value of 0 it’s black and when it has a value of 255 it’s white. Tones with values between these two extremes are grey. The higher the value, the lighter the grey.
An alternative system followed by some photo editors like Affinity Photo is to use a percentage value. When an image tone is 0% it’s black and a value of 100% is white. Again, any values between these two extremes are grey. You can see the two systems in the illustration below.
The Photoshop Levels Dialog
Now that you understand image tones, let’s look at how this translates into the Photoshop Levels adjustment. You can see the controls of the Levels adjustment in the following screenshot of the Photoshop Properties window.
In the Levels adjustment you can see there is a histogram representing the tones in the image. The histogram shows the distribution of tones across the image from black on the left to white on the right. Just below the histogram, you can see three-pointers with numbers just below these. The correct name for these pointers is Levels.
The level on the left with the number 0 below it is the Black Level. On the opposite side, we have the White Level with a value of 255. Hopefully, you will recognise these values from image tones section above. In the centre, we have the Midtone Level which has a value of 1 below it.
Now look closely at the black level and notice the histogram doesn’t extend all the way to the left but stops short. This tells us that there isn’t a black in the image and that the darkest tone is dark grey. The same is true of the other side where there is only a thin white line extending over to the right.
Applying a Levels Adjustment
Without black and white points in the image, the image will lack contrast and appear flat. This may, of course, be what you want, for example, a photo of a foggy scene would be low contrast. But if this isn’t ideal, you can use the levels adjustment to correct the image tones. All you need to do is drag the black and white levels in towards the centre to meet the histogram. You can see an example in the screenshot below.
Notice how in the screenshot the black level is showing a value of 8. What this means is that all the tones in the image that have a value of 8 or less are remapped to a value of 0. Over on the right side, you can see the white level has a value of 239. This means all the image tones that have a value of 239 or greater are remapped to 255. Photoshop then redistributes the other tones in the image (between 8 and 239) across the tonal range (0 to 255).
In the example above we adjusted the Input tones of the image to give them new values. We call these new values the Output levels. If you go back to look at the Levels dialog, you will see there is a second strip along the bottom of the dialog with a black and white level at each end. Below this, you will see “Output Levels” followed by two numbers.
These levels allow you to control the output levels when making a levels adjustment. The black output level on the left controls the first number, 0 in the above example. The white output level controls the second number, 255 in this example.
If we were to change the black output level to have a value of 30, this would mean the darkest tone in the image was a dark grey with a value of 30. In the above example, the black input level is set to 8 which remaps the tones with a value of 8 or less to whatever value is set by black output level.
This can be a little confusing to understand initially but it’s worth the effort. To help, I’ve produced the following video.
The Levels Adjustment Video
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The Levels adjustment is a very powerful tool that you’ll find in many different photo editors. Spending a little time learning how the Photoshop Levels adjustment works is worth the effort as you can then translate this knowledge to other photo editing tools.
This tutorial is one in a series of video tutorials explaining common editing tools that are found in different photo editors. If you would liked this tutorial, you might also like the next in the series that explains how the curves tool works.
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