The Venerable S-Curve

Posted May 27th, 2011 by   |  Photography, Software  |  Permalink

There are many plugins and special software products designed to help you enhance your photographs. I use a lot of them and think they are extremely helpful for our digital workflow. However, I hear from lots of people that they don’t want to use all the fancy software. Rather, they just want something simple they can use to make their photographs look better.

One of the most widely available tools in photo software is the curves control. In fact, just about every piece of modern imaging software includes a curves control. Using the curve is simple and doesn’t require much knowledge to quickly improve the look of an image. The fundamental purpose of the curve is to adjust brightness and contrast. Since most images need just a hint of extra contrast in order to pop from the page, doing this with a curve is sometimes the fastest way to improve the photo.

To activate a curve in Photoshop, add an adjustment layer or simply type CMD/CTRL + M on your keyboard. In Lightroom 3, go to the develop pane and adjust the curve from there. With Nikon Capture NX2, add a New Step, then choose Select Adjustment –> Brightness/Contrast –> Curves.

When the curve starts out, it will be a straight line. Your goal is to make the darks (shadows) just a bit darker while simultaneously making the brights (highlights) just a bit lighter. You do this by making an S-Curve like I show in the examples below.

To give the photo a little extra pop, all I did was add a simple S-curve in Photoshop CS5.

To give the photo a little extra pop, all I did was add a simple S-curve in Photoshop CS5.

Same photo, but no S-curve. This is the default curve; a straight diagonal line.

Same photo, but no S-curve. This is the default curve; a straight diagonal line.

The lower left part of the curve adjusts the shadows and the upper right part of the curve adjusts the highlights. If you move any section of the curve down (below the diagonal line), it will make that brightness darker. The same, but opposite is true if you move any section of the curve up (above the diagonal line).

Moving the lower left portion down (darker) and the upper right portion up (brighter) adds contrast to your image. You are effectively making the darks, darker and the brights, brighter.

Easy!

Here’s one more example on an old barn door just to make it clear.

With an s-curve.

With an s-curve.

Here's the original picture without an s-curve.

Here's the original picture without an s-curve.



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