Wednesday, June 4, 2008

Even more colour management

Today, I want to delve further into the issue of colour management. The topic came up in a discussion recently and I think it warrants a little more space here.

When you turn on colour management  in Photoshop's Color Settings, it uses ICC profiles (or color profiles) to ensure consistent and precise colour reproduction between devices.

That being said, in a colour managed workflow, an input device (camera, scanner, etc.) uses input profiles to describe the data it's captured. Photoshop uses the input profile and the output profile of your monitor to display colours accurately (or the output profile of your printer to print accurately).

Monitor output profiles describe colour gamut and characteristics such as colour temperature, white point, phosphors, gamma, and so forth. Printer profiles describe the ink and paper combination that you've chosen, dot gain, and the like. Photoshop takes the input profile of the image and converts it to the output profile of the printer in order to reproduce the colours accurately.

A couple of points to remember, the Assign Profile command, Edit>Assign Profile, changes only the description of how the numbers that describe the document will map to the colour space of the output device. Assign Profile only changes the appearance, not the underlying data.

The Convert to Profile command, Edit>Convert to Profile, changes the raw numbers to the colour space described by the target profile. As you are changing values, use this command with care.

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