Photoshop Tips: Curves Adjustments
The Curves Adjustment is one of those photoshop tips that every digital photographer should be familiar with.
Image -> Adjustments -> Curves...
This adjustment offers the most simple way to make non-linear changes to the tonal range of a picture. The window below shows a sample image along with it's histogram wth a straight diagonal line over the top. This line is the control for the changes you are about to make; you can click anywhere on the line and drag that point up or down.
Photoshop forms the control line into a curve which best matches the point(s) you give it - and the curve means that there is the best transition between the tones either side of your control point.
It is important to note that the point on the line that you click corresponds to the histogram; black to the left and white to the right. So lowering the control line at the left hand side will make the dark areas of the image darker and raising the line towards the right will make the lighter tones brighter.
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Dragging the curve upwards makes the image brighter. As you can see in the example below this can have the effect of 'blowing out' highlights (i.e. making them pure white) and reducing or eliminating texture. This is commonly used as a flattering technique as skin looks perfectly smooth.
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Similarly, bending the control line downwards makes the picture darker, as in the example below. Very often this removes areas from the picture by making them very dark or even black - this forces the viewers attention back to the lighter areas of the image.
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S-Curves
Most often I use an S-curve to both boost the light tones and decrease the dark areas, as in the example below.
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This single technique produces a more striking, somewhat stylised image. As it is so simple to do, I use it a lot (and you will find a lot of other photographers do too). If you browse through the gallery you will see lots more examples.
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