Gimp Addict -> Contrast Operations

Here's an brief explanation of each of the techniques shown below. Each one has it's place in digital editing.

• S-Curve - Use curves to increase global contrast. It gets its name from the shape of the curve. It tends to remove details in shadow and highlight areas.
• Contrast Mask - A blurred inverted mask applied to the layer to reduce global contrast. This tends to flatten the overall image.
• Unsharp Mask Local Contrast Enhancement (USM LCE) - Using unsharp mask with a high radius and low amount to increase local contrast with a limited effect on global contrast.
• Highpass Filter Local Contrast Enhancement - Use a large radius high pass filter overlay to increase local contrast with a limited effect on global contrast (tutorial coming soon).
• Tone Mapper - Decreases global contrast while improving local contrast.

Mouse over the links to see the effect on the image.

S-Curve || Contrast Mask || USM LCE || Highpass Filter || Tone Mapper