Written Tutorial Starts:
1. Opening Curves
Before we learn about the Curves Dialog box, we’ll need to open it up. You can make a quick adjustment on your image with Curves by going Image>Adjustments>Curves. I prefer working with Adjustment Layers, it’s cleaner and you can control the Adjustment Layer just as if it was any other Layer (enter Blend Modes and Opacity.) Let’s go Layer>New Adjustment Layer>Curves. I’ve given my Curves Adjustment Layer the name “Main-Tone-Adjustment.”
2. Looking at Curves
Double click on the Curves icon in your Layers panel to open the Curves dialog box. You will see a diagonal line straight across a grid and a histogram in the background and it’s all just looking a little crazy. No fear, we’re about to conquer this in the next few minutes.
3. How Does This Work?
The key to Curves is that we click on the diagonal line to add a point. We can also add multiple points. Points are draggable. When you drag a point up you add white to the image (brighten it), but when you drag down you add black (darken it.) I’ve visualized this with the screenshot above. Up = Brighten. Down = Darken.
4. Adding & Removing Points
Click anywhere on this line to add a point. Click somewhere else on the line to add a second point. You can now select any point and drag it up and down or just use your arrow keys to nudge the point up, down, left, or right. Grab your points (one at a time) and move them around to really mess up your image. After looking at the mess you’ve made, select your added points and just drag them off the Curves dialog box and drop them anywhere on your screen to remove the point from the line. This is how you remove unwanted points.
5. Brighten or Darken Your Image
Add another point to the middle of your line and drag it upward to brighten your image overall. Brightening and darkening the entire image is one of the easiest things to do with Curves. I’ve dragged my line up to brighten my image.
6. Adjusting Specific Parts of the Image
When I made the overall adjustment with Curves, my foreground was brightened up nicely, however the sky became far too bright. Using Curves we have the power to adjust only the darker portion of our image and keep the sky set at the brightness we want. Let’s look at the Curves dialog box again to see how this works.
7. Lights, Midtones, and Darks
When we look at the Curves dialog we can quickly identify which part of the line to pull up or down simply by understanding what parts of the image each part of the line adjusts. As you can see in the screenshot, the left side of the Curves dialog covers the darker tones in the image, the middle section covers the midtones, and the right side covers the lighter areas of the image. If we want to brighten the darker areas of this image but not brighten the sky (which is the lighter part of the image), we would add a point to the left portion of the line and pull up, then on the right side of the line we would pull down to darken those bright areas. See the next step.
8. Make Curves Work
Check out my screenshot and see how I have dragged up in the darks zone to brighten up the darker foreground area of this image, but I’ve dragged down the point I added in the lighter area to darken the light areas to create an image that looks much better and has much more detail.
9. Adding Contrast
If you have a keen eye, you’ll see that we essentially just removed contrast from the photograph. The problem now is that the photo is too flat -it just lacks contrast! We can fix this with with Curves as well. Matter of fact, contrast adjustments may be one of the things that Curves is used for more than anything else. To keep things simple, create a new Curves Adjustment Layer. This Adjustment Layer will be just for our contrast adjustment.
10. The “S” Curve for Contrast
To create contrast in an image we want to brighten the lighter areas and darken the darker areas. We do this with Curves by dragging down in the dark tones area and dragging up in the light tones area of the Curves dialog box. Check out the simple ”S” curve that I’ve made.
11. Trouble with Curves: Flat Spots
There are a number of things to watch out for when working with Curves. One of the things that can make your image look very bad, very fast is the introduction of flat spots in the Curves line that you’re adjusting. A completely flat line, straight across, removes all contrast and leaves you with an image that is all 50% gray. Any spot along that line which flattens out removes all contrast from that “chunk” of the image (i.e. a flat spot in the middle portion of the Curves line would kill contrast in a portion of the midtones.)
12. Trouble with Curves: Correcting Flat Spots
You can see in my screenshot that I have a more realistic example of what you may encounter while working with Curves. The top end of my line is completely flat and my sky has lost all contrast and detail, in fact it’s become solid white. We correct this issue by dragging in a new point and bringing it down near the closest current point on the curve and adjusting it slightly to remove the flat spot. (See the second screenshot below.)
13. Trouble with Curves: Inverted Color (Downward Line)
Whoa, what happened there?! One of the reasons we open Curves, play with it, and close it (before we understand how Curves works) is because we all seem to run into the downward slope in our line which will take your image (or the “chunk” of tone it spans across in the Curves dialog) and make it look like a negative. The trick to fix this is simply to avoid downward slopes. We hate downward slopes.
14. Curves Tip: Click Areas in Image for Adjustments
Select the little Hand icon in the Curves dialog box to bring up an eyedropper. You can use this eyedropper to to hover over different areas of your image to get an instant display of where that exact point rests in the overall brightness/tone of your image on the Curves line. Click on that spot to drop a point, or click and drag up or down to brighten/darken. This can be a quick and dirty way of cleaning up frustrating or difficult areas of an image.
15. Curves Tip: Adjusting Colors
Not only can you control the brightness and contrast of your images with Curves, you can also add, subtract, or mix colors into an image in a beautiful and effortless way. Check out the “Channels” drop down menu in the Curves dialog. Each of these channels controls the color according to its name. It also controls the opposite of that color. Red/Cyan. Green/Magenta. Blue/Yellow. Pulling up on any of these lines adds the color of that channel, but pulling down adds the opposite color. See the screenshot for a visual reference.
16. Curves Tip: Adjusting Colors II
To give this image warmth and sunset-like color, I’m going to add some red by dragging a point up right in the middle of the curve. I’m also going to add some magenta to the darker areas by dragging down on the green channel line in the shadow area. NOTE: I pulled the line back to the normal area in the bright part of the line so my sky wouldn’t be too pink. I also want to add a fair bit of yellow to the sky. We’ll do this by placing a point generally in the “lighter” section of the line in the blue channel area and drag down a little (the opposite of blue is yellow, subtracting the blue adds yellow.) I also pushed the line back to near normal in the darker areas to keep them from getting too “heavy” with a yellow color cast.
17. Go Forth…
Go forth and wield thine newfound Curve-tastic abilities and adjust, beautify, and revitalize your images and photographs in a snap with the most powerful adjustment option in Photoshop!