Curves is the master adjustment, one ring to rule them all etc. Learn Curves if you learn nothing else.
Heres the Curves window:
It looks like a graph because it is. It graphs the value range change that you impose upon the image. Here's how you read it.
The Curve above is its default state and represents no change. Below is a curve adjustments that represents a multiplation value of 0.5.
Multiplication? Say whu?
So... what is a multiplication? Well... they call it digital art because, at its root, it is derived from numbers. In the digital world black is 0 (zero) and white is 1 (one). The graph above can be read in the following manner:
- If 1 is multiplied by 0.5 the result is 0.5.
- If 0.5 is multiplied by 0.5 the result is 0.25
- If 0 is multiplied by 0.5 (or indeed any other number) the result is 0.
So... color adjustments are mathematics. These maths are (for the most part) quiet simple.
I will drive this fact home with a small demo. In the image below the left half has had a layer of mid grey (50% brightness) placed above it and set to Multiplication Blend Mode. This will multiply the image by 0.5. The right half has had a 0.5 multiplication curve applied as an adjustment layer. As you can see, they are both identical.