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Unless otherwise noted all contents and images on this site are copyright © 2001-2008 Roger Cavanagh
and may not be used without permission.
Labelled with ICRA
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Unless otherwise noted all contents and images on this site are copyright © 2001-2008 Roger Cavanagh
and may not be used without permission.
Labelled with ICRA
Two common input devices are digital cameras and scanners. An image generated by either is only fully defined, if tagged with an embedded ICC profile. Likewise, output devices such as monitors and printers can have ICC profiles to describe how they reproduce colour.
Some common colour standards are sRGB, an attempt by Microsoft and HP to standardize across devices, Adobe RGB (1988), and Apple RGB. There are many more. In the Windows world, untagged files are usually sRGB. An application can be CMS aware or not. If it is not CMS aware, it probably works in the sRGB colour space. If it is CMS aware and opens a non-tagged file, it probably assumes the file is sRGB. Because of the market dominance of Microsoft and Adobe, sRGB and Adobe RGB are very popular colour spaces. Also, because Macintosh computers are widely used in the desktop publishing industry, Apple RGB and ColorMatch RGB are popular.
A particular digital camera generates an image file and may or may not tag it with an ICC profile to describe the colour space of the file. Some cameras, such as the Canon 10D, give the user the option of using either sRGB or Adobe RGB.
The table below describes two particular cameras for illustration. The Canon Powershot G3 works strictly in the sRGB colour space. The Canon EOS 10D has a user option for sRGB or Adobe RGB (1998), user selectable by menu.
Notice that any image files generated by these two cameras will either be tagged as sRGB or not tagged at all. Nevertheless, the 10D can produce JPEG files in two colour spaces even though the camera designers did not see fit to tag Adobe RGB JPEG files (apparently, the fault of JEITA who created the EXIF 2.2 specification). The fact that an image file is not tagged does not mean it has no colour space. It simply means the file has not yet been tagged with the appropriate profile. Raw files tend to be proprietary among various camera manufacturers. Canon raw files are in the sYCC colour space, which apparently cannot be used as a working space like sRGB or Adobe RGB. Conversion programs always convert them to another colour space, such as Adobe RGB or ProPhoto RGB.