One of the most valuable editing tools a photographer can master is the Curves Adjustment Layer. Curves allow you to adjust your image’s exposure, contrast, and color tone at a high level. There is much to learn about Curves, but overall, the function is straightforward and gives excellent results.
Once you understand how to use Curves in Photoshop, the possibilities for adjusting and styling an image will become endless.
What Are Curves In Photoshop?
Photoshop’s Curves function allows you to adjust the exposure of your image by working with the Blacks, Whites, Highlights, and Shadows across a range of color tones.
The Curve is represented on a graph as a straight diagonal line. The lower left corner represents shadows and black areas, while the upper right corner of the graph represents highlights and white areas. The midtones of the image sit around the center.
The graph’s vertical axis represents the output levels (the new adjustments you make on the curve), while the horizontal axis represents the input levels (the image’s original values).
You can add and move points along the line to adjust the exposure, and the shape of the curve will change to reflect the adjustments in the image. As you drag up, you add brightness, whereas dragging down makes the area darker. The steeper an area of the curve becomes, the more contrast you’ll see in your image.
How To Access Curves In Photoshop
It is helpful to know the different ways you can access and apply Curves in Photoshop, as the method you use may vary depending on how you want to edit your picture.
Option 1: An Adjustment Layer
If you’d like to apply Curves as an Adjustment Layer, head to the Layers Panel and click the Adjustment Layer icon at the bottom of the panel.
From the options that appear, click Curves.
You can apply a Curves adjustment layer with a single click if you’ve got the Adjustments Panel open in your workspace. Simply click the Curves icon from the available options.
The Curves Adjustment Layer will appear in the Layers Panel above the layer that was previously selected.
In the Properties Panel, you’ll see the Curve and its settings ready to use.
Applying a Curve as an Adjustment Layer is helpful because you can go back and edit the curve at any time by double-clicking the Layer Thumbnail in the Layers Panel.
This method is also useful if you’re applying curves to the layer below by adding a clipping mask.
Option 2: As A Smart Filter
The other method is to apply Curves as a Smart Filter. Smart Filters are non-destructive, so you can easily remove the edits by deleting the Smart Filter without permanently altering the image.
To apply curves as a smart filter, you first need to convert the image to a smart object by heading to Filter > Convert for Smart Filters.
In the Layers Panel, the image layer will change to Layer 1, and the thumbnail will now feature the Smart Objects icon.
From there, head to Image > Adjustments > Curves.
The Curves window will open, and you can make any adjustments.
Once you finish adjusting the Curves, the Curves adjustment will appear in the Layers Panel as a new Smart Filter beneath the Image Layer. You can double-click Curves whenever you want to return to the curves to make further adjustments.
How To Use Curves In Photoshop
Adding & Removing Anchor Points
Adding an anchor point is easy: just click along the line in whichever tonal area you’d like to adjust – the darker tones sit at the left of the graph, while the lighter tones sit at the right. Midtones sit around the center.
So, if I want to add an anchor point to adjust the shadows, I’ll click along the left side (but not all the way at the left border of the graph, as that area represents the darkest blacks of the image.) You can add as many anchor points as you’d like along the curve.
You can remove an anchor point by holding Control (Win) or Command (Mac) while clicking the anchor point. If you’ve added multiple anchor points and want to start fresh, you can remove them all by clicking the Reset icon at the bottom of the panel.
Using The Curves Preset Menu
At the top of the Curves Panel, you’ll see the Preset drop-down menu. Click the drop-down arrow to view the presets.
While the Curve is an excellent tool for making slight adjustments to the tonal range of an image, you can use the Presets to make quick and simple adjustments to the contrast and exposure of the picture.
For instance, if I want to increase the contrast using the Curve quickly, I can select one of the contrast options.
This will automatically add and move anchor points on the curve, adding contrast to the image and providing a base to work off of and adjust further.
Adjusting Exposure & Contrast Using Curves
Adjusting the exposure of an image is easing using curves. Add an anchor point at whichever point along the tonal range you’d like to change: Shadows, Highlights, or Midtones.
For instance, if I want to increase the shadows, I’ll add an anchor point towards the left and drag it up until I’m content with how the shadows look.
This has increased the overall exposure of the image.
However, because the only anchor point is the one representing the shadows, the rest of the curve is free to move along with the shadows adjustment, meaning the midtones and highlights of the image will be affected, too.
If this doesn’t work for your image and you want to adjust the shadows but leave the midtones or highlights relatively the same, you can add an anchor point in the center for the midtones and/or the upper right for the highlights and drag the points back down to the original line.
Again, this is optional, and each image will require a different set of anchor points. You may only need one, or you may want to add several.
Otherwise, if my goal is to increase contrast, I can do so by bringing the shadow’s anchor point down, and the highlight’s anchor point up, creating a steeper curve – known as an S Curve.
An S Curve will increase the overall contrast in your image.
Using The Color Channels Within The Curve Adjustment
Aside from the RGB channel, the curve features three color channels that you can use to adjust the image’s color tone: Red, Green, and Blue. You can use these channels to color-correct the image or adjust the color grading to give the image a certain mood or style.
To switch between the channels, click the RGB channel drop-down in the Properties Panel.
Then, select which channel you’d like to work in.
The same idea applies to the Color Channels as to the RGB channel. If I were to add an anchor point in the shadows area and drag it up, it would add more of that color to the shadows. Dragging down would add more of the opposite color.
So, if I wanted to add a bit of Green to the darkest areas of my image (creating a film effect), I’d head to the Green channel.
I can then click the anchor point that already exists all the way at the bottom left corner of the Curve – the area representing the Blacks in the photo – and drag it straight up, adding green to all the darkest parts of the image.
This gives the image a more dramatic and moody appearance than the original.
How To Color Correct Images In Photoshop Using Curves
As mentioned, you can use the color channels in the Curves panel to color correct an image or add style through color grading, depending on your needs.
To Color Correct an image using Curves, click the Color Channel you’d like to use. For instance, if I want to warm up a picture, I’ll head to the Blue channel – not because I want to add Blue to my image, but because I want to reduce it, thus adding its opposite: yellow.
I can then add an anchor point in the center of the curve (the Midtones) and bring the point down, reducing blue tones and adding yellow tones.
The resulting image has a warmer look that is more accurate to reality and better fits the summery visual style I’m going for.
However, there appears to be a slightly greenish tone in the shadows, so I’ll head to the Green channel, add an anchor point in the shadows, and drag it down slightly.
That adjustment has corrected the green tint in the shadows.
Now, I’ll add a bit of Magenta to the highlights in the sky. Magenta is the opposite of Green, so I’ll stay in the Green channel and make a new anchor point in the upper part of the highlights, which I’ll drag down a bit.
I’ll also add an anchor point in the midtones, just below the original line, so that the Greens are reduced slightly, but the Magenta doesn’t affect the rest of the image too much.
The image now has a slightly warm, rosy tint that perfectly matches the style I’m going for.
Feel free to play around with the Color channels, as each image and visual style may need different channel adjustments.
Curves VS Levels In Photoshop
Curves and Levels can be used to adjust an image’s overall exposure or contrast. However, while Curves allow you to add and move points along a graph, Levels only enable you to move three points – lights, darks, and midpoints – along a horizontal line.
Working with Levels will still allow you to lighten or darken the entire image, and you can also adjust the black or white points to create more contrast. But you won’t be able to further change the relationship between the tones in the image.
With Curves, you can make much more subtle adjustments, adding as many anchor points to the curve as you need to adjust one tone while leaving others as they were originally.
This means you can change only the light tones or only the dark tones, or you can adjust only small, specific areas of the image’s tonal range – such as the darkest midtones or lightest shadows.
With Curves, you have nearly total control over a photo’s exposure and contrast (as well as color grading). And because the graph in the background of the curve shows the histogram, you can constantly monitor the balance of tones in your image.
Overall, Curves is an easier to refine and more versatile adjustment for your photos.
To learn more about how Curves fits into your entire photo editing process, see my 10-Step guide to photo editing in Photoshop here.