Color Correction Using Curves

Topics covered in this Photoshop tutorial:

Color correction with a Curves adjustment layer, Adjusting brightness and contrast with Curves, Setting white, black, & mid points

Exercise Preview

Exercise Overview

In this exercise, you’ll learn how to use Curves to adjust an image’s color and brightness/contrast. Curves may be less intuitive than other techniques, but it’s one of the most powerful adjustment tools in Photoshop.

Getting Started with Curves

1. From the Photoshop Class folder, open 2D Woman.jpg.

2. Choose View > Fit on Screen.

   This image has a yellowish tint, which is especially noticeable in the light areas (which are called highlights).

3. At the bottom of the Layers panel, click the Create new fill or adjustment layer button and from the menu, choose Curves.

4. In the Properties panel on the right, you’ll see a “curve” line (that is currently straight) comparing the image’s original range of shadows, midtones, and highlights (input) to the corrected range (output).

5. At the top of the Properties panel, click on the RGB menu and choose Blue.

6. Most properly exposed and color corrected images will have the histogram (the peaks that look like a mountain range) evenly spread between the darkest black and brightest white. Any empty areas (no peaks) of the histogram on the far left or right indicate that the image’s pixels are not properly mapped to the range of dark to light. We can remap them by bringing in the black point on the left and white point on the right.

   In this case we only see an empty area on the right, so drag in the white point (drag it to the left) as shown below:

   

7. At the top of the Properties panel, click on the Blue menu and choose Green.

   Again drag in the white point as shown below:

   

8. At the top of the Properties panel, click on the Green menu and choose Red.

   Again drag in the white point as shown below:

   

9. In the Layers panel, click the eye next to the Curves 1 layer a few times to see how the whole image’s color is more accurate, but it’s especially noticeable in the light areas which are now a pure white instead of being so yellow.

   Make sure the Curves layer is visible before moving on.

10. Let’s see a more automated way to set the white points. It doesn’t always work, but it can be useful when it does. At the bottom of the Properties panel click the Reset to adjustment defaults button .

    This removes any work done on the adjustment and it’s as though we haven’t done anything with it yet.

Using the Set White Point Tool

1. At the top of the Properties panel, notice the menu should have been reset back to RGB (it’s not on Red anymore).

   This means we’re editing Red, Green, and Blue all at the same time (not individually).

2. On the left of the Properties panel, double–click the white point tool (it’s the bottom of the 3 eye droppers).

3. In the Color Picker that opens, under the H, S, B settings make the B (which stands for brightness) setting 95% so when we use the tool it won’t blow out the highlights leaving no detail.

   • Click OK.
   • If it asks you to save the new target color as a default, click Yes

   NOTE: This means you never have to change this setting again, it will work on all future images!

4. To the right of the woman’s body, click anywhere in the bright white area.

   With just one click, the color should look great now!

5. Using the menu at the top of the Properties panel, flip though the Red, Green, and Blue channels to see it automatically pulled in the white points (like we did manually).

   NOTE: This does not always work, so it’s good to understand what’s going on and how to do things manually. Also, it may get you close, but then you can tweak the work it did by going into the channels and adjusting to your liking.

6. At the top of the Properties panel, change the color channel menu to Blue.

7. In the middle of the curve (which is currently a straight line), click to add a point and:

   • Drag down to make the photo more yellow
   • Drag up to make the photo more blue

   

   NOTE: If you don’t like the change, you can drag that point outside of the Properties panel and release to remove the point.

Adjusting Brightness & Contrast

1. At the top of the Properties panel, change the color channel menu to RGB.

2. In the Properties panel, you will likely see multiple diagonal lines, which are confusing. We can simplify the display by changing a preference.

3. Click on the Properties panel menu and choose Curves Display Options.

   • Next to Show, uncheck Channel Overlays.
   • Click OK.
   • Only one diagonal line should be left visible, which is used to adjust brightness and contrast (because you’re adjusting all colors equally).

4. As shown below, click on the line towards the lower left and drag down slightly to make shadows darker.

   

5. Click on the line towards the upper right and drag up slightly to make highlights brighter as shown here:

   

6. In the Layers panel, rename Curves 1 to color and contrast

More Practice with Curves

1. From the Photoshop Class folder, open 2D Eggs and coffee.jpg
2. Choose View > Fit on Screen.
3. At the bottom of the Layers panel, click the Create new fill or adjustment layer button and from the menu, choose Curves.

4. At the top of the Properties panel, click on the RGB menu and choose Red.

   As shown below, bring in black point on the left, and white point on the right.

   

   NOTE: Be careful about bringing in the points too far. That will clip more highlights and shadows, which means to force more areas into pure black and white. That can lead to a loss of detail in the highlights and shadows, and create too much contrast.

5. At the top of the Properties panel, click on the Red menu and choose Green.

   As shown below, bring in black point and white point.

   

6. At the top of the Properties panel, click on the Green menu and choose Blue.

   As shown below, bring in black point and white point.

   

7. In the Layers panel, click the eye next to the Curves 1 layer a few times to see the improvement in color and contrast. The shadows are no longer washed out (meaning they were light).

   The original image had a specific style of color (which in some cases may be desirable), but it’s nice to know how to take stock photos like this and alter them to fit your tastes!

   Make sure the Curves layer is visible before continuing.

8. Let’s brighten the image a bit. At the top of the Properties panel, click on the Blue menu and choose RGB.

9. As shown below:

   • Drag up the shadows to brighten them slightly
   • Drag down the highlights to darken them slightly

   

10. In the Layers panel, click the eye next to the Curves 1 layer a few times to see change so far.

    Make sure the Curves layer is visible before continuing.

11. At the top of the Properties panel, click on the RGB menu and choose Red.

12. Add a point around the middle of the line and:

    • Drag up to make the photo more red
    • Drag down to make the photo more cyan
    • End on a color balance that you find pleasing.

13. Repeat this process with the other color channels (Green and Blue).

    • Adjusting the Green channel will make the image more green or magenta.
    • Adjusting the Blue channel will make the image more blue or yellow.

14. In the Layers panel, click the eye next to the Curves 1 layer a few times to make sure you like your adjustments.

15. In the Layers panel, rename Curves 1 to color and contrast

Optional Bonus: Using Auto Settings with Curves

1. From the Photoshop Class folder, open 2D Tacos.jpg
2. Choose View > Fit on Screen.
3. At the bottom of the Layers panel, click the Create new fill or adjustment layer button and from the menu, choose Curves.
4. At the top right of the Properties panel, hold Option (Mac) or Alt (Windows) and click the Auto button.

5. Click on each of the 4 options (noticing how each affects the color of the photo):

   • Enhance Monochromatic Contrast
   • Enhance Per Channel Contrast
   • Find Dark & Light Colors
   • Enhance Brightness and Contrast

6. Once you’ve seen all 4 options, select Find Dark & Light Colors (which usually does the best job, and is the best for this photo).

   • Check on Snap Neutral Midtones.
   • Click OK.

7. At the top of the Properties panel, use the RGB menu to look though the Red, Green, and Blue channels to see the adjustments it made automatically for you:

   • Adjusting the black and white points
   • Adding points in the middle of the curve for the color balance of the midtones.

   NOTE: This Auto feature does not always work, so it’s good to understand what’s going on so you can do it manually and/or tweak things further when needed.

Using the Set Gray Point Tool

1. On the left of the Properties panel, click on the gray point tool (the middle of the 3 eyedroppers).

2. In the image, click on something that you think should be a neutral gray/white color (like the plate or wood).

   • Click on different areas until you’re happy with the results (or use Cmd–Z (Mac) or Ctrl–Z (Windows) to undo if you don’t like the change).
   • Each pixel you click on is a slightly different color, so as it’s turning that into a neutral color, it will affect the color balance of the whole photo.

3. In the Properties panel, flip though the Red, Green, and Blue channels to see the midpoints this tool added for each channel (which you could adjust more if needed).