What Are Curves and How Can I Take Advantage of Them?

Curves are possibly the most underused tool in the Photoshop arsenal, and they’re the heart of our tutorial today. Many people are put off of using them because they are not particularly intuitive and there are so many other tools available which are a bit easier to grasp out of the gate.

Unlike Levels, where the adjustments you make are applied uniformly across the image, the Curves are applied more granularly, which makes it much easier for you, the editor, to make very subtle changes to the image. If you want deeper shadows, brighter whites, or to isolate a particular shade of blue (now gray) in the sky framed in your photo, for example, you can do so with the Curves tool.

In the image above, you can see both the base photo and the unadjusted Curves readout of the image. Notice how the line from the lower left to the upper right is a nice clean, straight, diagonal line; our Curves, in other words, are pretty flat. The curves can seem a bit abstract, so let’s pick a spot on our photo and see where it falls on the curve. We’re going to click on the white side of the cup to sample that spot. Note: If you just click a spot and hold it, it will show you the spot on the curve, but if you hold CTRL and click it then there will be a permanent mark on the curve line:

Now, let’s look at that little black dot on that curve. Follow it with your eyes to the left gradient bar, and then follow it with your eyes down to the bottom gradient bar. That dot represents the slightly gray, almost white, value of the cup in the photo.

Because the curve is unadjusted, the input (the lower gradient bar) matches the output (the left-hand gradient bar). If we were to grab that little marker on the curve and pull it down it would darken the value, and if were to raise it then it would lighten the value. Let’s take a look at what happens when we do that in the next section of the tutorial.

Adjusting Your Image via Manual Curve Manipulation

The values for that particular tone as well as the entire curve have been changed. The previously slightly gray cup is now shockingly white and the highlights on the chrome of the espresso machine are much brighter (as is the rest of the image). There are some nice subtle changes to the image, such as in the reflections, and the shape of the Bakelite handle of the espresso portafilter is significantly better defined against the background now. It’s not a bad looking little image, and it’s a lot more visually interesting now than it was before.

What if we went the opposite route, though? What if we dropped the value way down instead of spiking it way up?

We couldn’t drop it all the way down because that would turn the picture almost completely black. Instead, we dropped it significantly below the starting line (the light gray line indicating the original baseline curve). You can see how it significantly darkens the photo and turns what was a bright coffee shop photo into something moodier. Clearly, the end result is a bit on the underexposed side, but we wanted you to see how dramatically a fairly small adjustment in the curve could change things.

Now that we’ve played with a single point on the curve and seen how it affects everything, let’s reset the curve. Hold down the ALT key and the “Cancel” button in the Curves box will turn into “Reset”. Click to reset the curve back to the state it was in when you opened the menu.

Let’s see what happens when we add more points to the curve. Go ahead and repeat the process we performed above to select one the lightest points in your photo (like our espresso cup) and then pick darkest point using the same technique. You’ll end up with a dot for the light and a dot for the dark on your curve.

This is where things get fun. We’ve just made an anchor point for the darkest and lightest parts of our image, Let’s get a little crazy with everything in between. Use the dropper tool to pick any portion of the image you’d like to adjust (or, since we’re being playful, just grab any point on the line) and make an adjustment. If you like it, leave it. If you don’t like it, slide it back into place. Feel free to tug and pull the curve as you see fit to create the image you’re looking for. After a moment or two of playing this is what we came up with:

You can see how, in playing with the curves, it’s possible to capture elements of our earlier two example images. We liked the brightness of the cup but we also liked rich moody shadows. A little fiddling with the curves let us bottom out some of the shadows, spike the intensity of the highlights, and enjoy the best of both.

Now that we’ve looked at manual curve adjustments, let’s look at the Curve presets.

Quick Manipulations with Preset Curves

We recommend manually playing with the Curves tool for a while until you get a real sense of how changing the curve changes your images. Once you’ve done that, however, you’ll likely find it invaluable to call on the Curve tool presets.

For example, in the last image of the previous section of the tutorial, we arrived at a pretty high-contrast image. The whites and highlights were fairly bright and the shadows were quite rich. Since we’ve established that we like high contrast images, the next time we go to use the Curves tool, we can pre-seed our image curve by selecting “Strong Contrast”. Let’s look at the curve it gives us for that preset:

The preset is essentially the curve we had in our prior image (except a bit smoother as it doesn’t have the extra pull on the highlights and lowlights that we put in). You can see how using the presents to jump in the direction you want to go and then finishing the job by making subtle changes to the existing curve is a much faster way to achieve the results you want than reinventing the wheel.

Playing with Black, Gray, and White Points

If you were worried that we had run out of fun tricks in the Curves menu, well, worry no more. We have another handy little trick to help you manipulate the curves and further enhance your black and white images. There’s a big part of the Curves menu pane we haven’t even talked about yet, and that’s the black, gray, and white adjustment droppers at the bottom of the pane.

Our work with black and white images makes these tools even more relevant. When we want to create high contrast images and really capture the crispness common in old black and white photos, it’s so easy to do so with a quick manipulation of the black, gray, and white points. Click on each one and select the darkest point in the image, a mid-tone gray point, and the whitest point in the image:

From here you can manipulate the curve and apply presets just like you did in the previous two steps of the tutorial.

Although many people are put off by the complexity of the Curves tool, we hope after a little tinkering you have seen how the extra effort is worth the time and yields really fantastic images.

Have a tip or trick to make convert photos to black and white and make them pop? Join in the conversation below.