The Levels tool allows you to make adjustments to the tonal range of your images. With Levels you can set black and white points, increase or decrease contrast, brighten or darken midtones and increase the amount of black or white in your image. Although it can also be used to adjust colour balance, I prefer to use other tools for that purpose.
The Levels tool always works on the full range of tones in your image.
Levels Properties
Presets: The dropdown offers some simple preset adjustments. I recommend you ignore these. When you make any other changes, the heading here will change from Default to Custom.
Auto: As the name suggests levels are set automatically when you click this.
The Levels Adjustment Layer Properties
Channel: This defaults to RGB. The dropdown allows you to adjust levels for each of the 3 colour channels. One way to adjust colour balance is to set the black and white points for each channel separately. You will need to adjust all 3 colour channels otherwise you will get some very strange results!
Histogram: This is a graphic representation of the range of tones in your image. Pure black is on the left and pure white is on the right. Knowing how to ‘read’ Photoshop (and in-camera and Lightroom too) histograms is an essential part of understanding how your images can be improved.
Black Slider: Move this to the right to add more black to your image. Any pixels to the left of this slider will be pure black. You can also set the black point by moving the slider to align with the left hand side of the histogram. Try holding down the ALT key and then click and hold your cursor on the Black slider. Your image will turn white. Drag the black slider slowly to the right until you begin to see pixels appearing. Release the mouse button and the black point will be set.
Midtones Slider: This is used to lighten (slide left) or darken (slide right) the midtones.
White Slider: This works in the same way as the black slider but inversely.
Output Levels: The default is set to 0 (pure black) and 255 (pure white). Moving either of these sliders will reduce the tonal range of your image and therefore reduce contrast. I rarely use this although it can be useful to lighten very deep shadows or to emphasise low contrast subjects such as a misty landscape.
Using the Levels Tool
Add a black and white adjustment layer. Your image will remain exactly the same.
Set black and white points by moving the sliders to align with the left and right edges of the histogram. This step may not be necessary. You may also wish to ignore the black and white points and just move these sliders to achieve a different effect.
Move the midtones slider left to darken the midtones, right to lighten them.
In some cases you may also choose to adjust the black and white output levels to reduce contrast or to lighten shadows. This can work well in some cases.
Examples
Example 1: a simple gradient ranging from dark grey to light grey.
Unedited Histogram
Move the slider to compare the unedited and edited versions.
Edited Histogram
The unedited histogram does not extend to the edges of the range. As a result there are no pure blacks or whites in the image. With the edited histogram, both the black and white sliders have been aligned with the histogram. This has stretched the tonal range and there are now pure blacks and whites. In other words, the contrast has been increased.
Example 2: a similar example but this time with an image.
Unedited Histogram
Move the slider to compare the unedited and edited versions.
Edited Histogram
Can you work out why the contrast has been increased in the edited version?
- Download this sample file.
- Open it in Photoshop.
- Add a Levels Adjustment layer.
- Set the black and white points. (There is no obvious right answer with this file so it’s best to do it by eye ie until it looks right!)
- Adjust the midtones slider until you are happy with the result.
