Colour space
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The colour space relates to how the stored digital values stored electronically are to be interpreted. No monitor or printer is capable of producing the full spectrum of light visible to the human eye. In other words, the gamut of visible light is much greater than the gamut of reproduction.
When an image is captured in Raw, it contains all the information which the sensor is able to gather. However, generally speaking, no more than 8 bits of this information per channel will be represented through the monitor or the print. A colour space weights this information in order to make the most use of the intended output device, as well as providing latitude for postprocessing. The image must be viewed in the recorded colour space for it to make sense. Not all equipment and software is capable of viewing all colour spaces. If it is not, a colour shift will result.
Common colour spaces in use are:
- sRGB - the standard colour space for most uses, and the one most widely capable of being reproduced
- Adobe RGB - an alternative colour space developed by Adobe and more suitable for images which are to be extensively postprocessed for the purpose of printing in CMYK.
- ProPhoto - an extended colour space with a greater gamut, but which can be viewed by a comparatively small group of software applications
Images are stored in 8 bit or 16 bit. Generally, a 16 bit image contains all of the values of the original Raw file, and therefore can be freely converted from one colour space to another. An 8 bit image contains a reduced set of values, so repeated colour space conversion may result in image degradation.
In addition to colour space, images are stored in a variety of colour modes, of which RGB is the native mode for photography, whereas CMYK is the native mode for commercial print. In postprocessing, use of the LAB mode has many advantages, for example when working with curves.
