Adding contrast to an image without a saturation boost
Here’s a quick tutorial on how to add contrast to an image in Photoshop without boosting saturation.
Quite often we need to add contrast to an image to give it more punch and bite. There are several ways to accomplish this in Photoshop but the way that gives us most control is to use an adjustment layer. By using an adjustment layer to add contrast (instead of just using the brightness/contrast slider) or Image/Adjustments/Curves we can put the curves adjustment on its own layer and decouple the curves adjustment from the resulting, often unwanted saturation boost that can occur with the first two methods.
Here’s how its done.
Take this image of some grass. It’s very flat and needs some contrast added.
Add a curves adjustment layer by either:
- selecting Layer/New Adjustment Layer/Cuves and click “ok”; or
- click the adjustment layer icon on the bottom of the layers pallette and select ‘curves’
This brings up the curves dialogue box.
Now, to add contrast to your image, select a point 1/3 the way along the line (from left to right) and pull it down (click and drag the point with your mouse). Then select a point 2/3 the way along the line and pull it up. This is easier to show than write. It should look something like this when you’re done - this is called an s-curve because it looks like the letter “s”:
Click OK.
Your layer pallete will now have a curves adjustment layer on it and will look like this:
Note the red box. That’s the blending mode and it defaults to normal. This box is the key to decoupling the contrast boost we’ve just applied from an increase in contrast.
Now your image should look like this:
Nice bit of contrast added there but can you see that as a result, the saturation has increased too? You may like this! Adding contrast always adds saturation when you are in Photoshop’s default normal blending mode so you can use it to add punch and vibrance.
But what if you think that the grass looks too vibrant, too green, a bit false…..
Then set your blending mode via the dropdown selector on the layers pallette (highlighted by the red box) to luminosity mode:
This now applies the curve adjustment we made to the luminance or brightness information only and not the colour channel information. So you get all the contrast without the saturation boost.
Here’s our image with a contrast s-curve in luminosity mode:
You can use this technique on any adjustment layer where you only want to affect the luminance or brightness information and not the colour. It is a much more controllable method than adding contrast then decreasing saturation (using the hue/sat sliders) and less destructive to the image.
PP
