In Pt. 3 we looked at the Levels tool. Now let’s turn to Levels’ big sister: Curves. The Curves tool works well for colour photography but it is especially useful in B&W photography because it can be used to make fine adjustments to tonal values in an image. Where Levels offers three controls, black, white, and midtones, Curves offers up to fifteen adjustments points.
The Curves tool scares a lot of beginners because it’s not as intuitive as Levels but Curves are quite logical once you get the hang of them. Alas, there is no proper Curves tool in Photoshop Elements, though there is a Color Curves tool that is really little more than Levels presented another way. Photoshop and Gimp have a fully-featured Curves tool.
So, let’s take a starting image, a cell-phone shot I took in a coffee shop:
Converting this to B&W using Channel Mixer and using the Green filter preset, I get this for a starting point:
Because of the inherent contrast in the image, it’s already looking pretty decent, though it’s a bit dark. To tweak the image I turn to the Curves tool, which looks like this in Photoshop:
So, where’s the curve? All we see is a straight diagonal line going from bottom left (blacks) to top right (whites). The answer is that we start with this straight, diagonal line and pull and push on it with our mouse to see what effect it has on our image.
Starting then, on a duplicate background layer, let’s call up Curves and tweak the line around a little and deliberately overdo it to see what effects we can get.
I’ve placed two anchor points on the line to make the kind of S-shaped curve that would normally be just about right to add some zing to the image, but in this case the image is already contrasty and the adjustment makes it overly contrasty, unless you’re going for a silhouette image. The dark areas in the image were already quite dark and I’ve pulled them down into the blacks and have lost a lot of interesting detail.
To reset Curves back to its original state, click Option-Reset (on a Mac) or Alt-Reset (Windows). Now let’s do something wild and really distort the image:
This time we get an image that is distorted and nearly solarized. There may be times when this might be just the right kind of treatment for an artistic presentation, so keep in mind you can do experimental images using Curves.
Now, let’s Reset Curves, and try for a more conventional B&W image:
Notice I’ve used 5 anchor points to give Curves a boost to lighten up the midtones but keep the blacks a deep, rich black. The final image, then, with a little sharpening added, looks like this:
For practice, try adjusting an image (always on a layer) with first the Levels tool, then the Curves tool, to get a feel for the difference between them. The Levels tool is good for most images, but the Curves tool offers more sophistication and is especially useful for images that are hard to get just right.
For more detailed information on using the Curves tool, here are some excellent online articles you may wish to read.
Next time we’ll explore Photoshop’s secret weapon: Layer Masks.