How to Use Photoshop Curves

Photoshop Curves Tutorial

Many new Photoshop users don't know where to start when it comes to learning the basics of the program.  While Photoshop is quite complicated, it doesn't need to take years to become comfortable with it.  So, with that in mind, I wanted to write a series of posts that will help new Photoshop users learn some of the absolute basics of Photoshop editing.

In this tutorial, I will show you how to use Photoshop Curves - the BEST and most powerful tool to use in Photoshop to adjust the overall brightness and contrast of your image and to shift color tones.

How to Open a Curves Layer

To open a new Curves layer, select Layer>New Adjustment Layer>Curves (if you are not familiar with editing with Layers, check out our post on how to use Photoshop Layers):

What Do Curves Do in Photoshop

As you can see below, the Curves panel shows a histogram and a graph of your White Point, Highlights, Midtones, Shadows, and Black Point. Each section is exactly what it sounds like:

• White Point is the whitest white.
• Black Point is the blackest black.
• Highlights are the brighter portion of your images.
• Shadows represents the darker portions.
• Midtones represents everything in between.

Always remember that when you adjust one point in the histogram, another point will be affected.  For example, if you adjust your highlights, your shadows will also be affected.  Editing curves involves a lot of push/pull, and tinkering until you are satisfied with the results.

Global Curves Adjustment Using the RGB Channel

To keep things simple, let's start by looking at the RGB (Red/Green/Blue) channel.  You can edit various color channels individually, but for now, let's just look at editing the overall RGB channel, rather than individual channels:

Adjusting the Curves will increase the overall contrast of your image, as well as the brightness.  In order to make a quick increase or decrease, simply click the midpoint of the diagonal line and pull up to the left (brighter) or down to the right (darker):

Two common types of curves adjustments are the S-curve and the inverted S-curve.

• The standard S-curve will increase the contrast of your image, which means there will be a noticeable difference between your highlights and shadows.
• The inverted S-curve will decrease the contrast of your image.

Curves adjustments CAN be layered on top of one another.  Below, I have made three curves adjustments in three different layers:

My first two adjustments were S-curves, but in my third adjustment, I moved only one point on the diagonal line instead of two.  As you can see in the third curves adjustment above, I moved my Black Point (bottom left of the histogram) up slightly - this creates a hazy effect on the image.  The reverse is also true: if you move the White Point (top right) down, the image will become darker.

Now that we have covered curves using the RGB channel, lets take it a step futher and talk about curves using the INDIVIDUAL red, green and blue channels.

Global Curves Adjustment Using the Red, Green and Blue Channels

Create a new Curves layer by clicking the icon highlighted here:

In the drop down menu on your Curves panel, you will see that there are four channels: RGB (red, green and blue combined), Red, Green and Blue.

When you select a certain color channel, only that particular color will be affected.

Working With Individual Color Channels

Since the image in this example has an abundance of red - not only in the poppies but also the image has an overall red cast - I have selected the individual Red channel:

When pulled towards the upper left, more red is added to the image.  To reduce the reds, we need to pull the channel towards the bottom right of the curves histogram.

This would be the same for the Blue and Green channels, as well: pulling to the top left increases a color and pulling to the bottom right will reduce it.

As you can see here, pulling to the bottom right significantly reduced the reds:

Since the image still has a bit of a red cast, I also pulled up in the Green channel, as green cancels out red:

I also pulled up a bit in the Blue channel:

As you can see in the Green and Blue channels, I made sure to pull up on the highlights (near the top of the diagonal line) as this is the area that represents midtones to highlights.  The subject's face still had a lot of red, so by adding in some green and blue, that helped balance the skintone.  I finished off by making one last boost to the RGB channel:

Local Curves Adjusment

In the previous examples, we made global adjustments to the overall tone of the image, but just like any type of adjustment in Photoshop, you can also make local adjustments to Curves using Layer Masks.

If you are unfamiliar with Layer Masks, you can read our post on Layer Masks to get caught up! 

For the image below, I want to make a local adjustment to the wall behind our subject in order to bring out the blue:

In order to do that, I created a new Curves Layer Mask, and pulled up in the Blue channel to make the blues pop.  I then used a black brush with a soft edge to erase the curves adjustment from everything except for the wall.

I want the wall to be more blue, not the subject:

After adjusting the Blue channel, I noticed that the subject had a bit too much red on her face, and there was some red showing up on the wall (you can see it in the left side of the frame near the subject's arm in the image above).

So I created new Curves Layer, but this time I pulled down in the Red channel.

Here is the Before/After example of the curves adjustments I made:

Conclusion

This is the absolute nuts and bolts basics for understanding curves in Photoshop, but more than enough to get you started on making some clean and simple edits.  Be sure to play around with the Curves panel on your own to experiment!

Looking for Photoshop Actions to help you quickly adjust the Curves in your workflow?  Be sure to check out the PURE Color Workflow!

Do you have any questions or comments about Photoshop Curves?  Leave us a comment below - we would LOVE to hear from you!  And PLEASE SHARE our tutorial using the social sharing buttons (we really appreciate it)!