Adobe Photoshop CS5 for Photographers - Martin Evening [273]
If you are using Photoshop 6.0 or later it does not matter so much which RGB color space you choose in the RGB setup, as long as you stick to using the same space for all your work. RGB to RGB conversions are not as destructive as RGB to CMYK conversions, but the space you plump for does matter. Once chosen you should not really change it. Plus whichever color workspace you select in the RGB color settings, you will have to be conscious of how your profiled Photoshop RGB files may appear on a non- ICC savvy Photoshop system. What follows is a guide to the listed RGB choices.
Apple RGB
This is the old Apple 13" monitor standard. In the early days of Photoshop, Apple RGB was used as the default RGB editing space where the editing space was the same as the monitor space. If you have legacy images created in Photoshop on a Macintosh computer using a gamma of 1.8, you can assume Apple RGB to be the missing profile space.
sRGB IEC-61966-2.1
sRGB was conceived as a multipurpose color space standard that consumer digital devices could all standardize to. It is essentially a compromise color space that provides a uniform color space which all digital cameras and inkjet printers and displays are able to match (since sRGB aims to match the color gamut of a typical 2.2 gamma PC display). Therefore, if you are opening a file from a consumer digital camera or scanner and there is no profile embedded, you can assume that the missing profile should be sRGB. It is an ideal color space for Web design but unsuitable for photography or serious print work. This is mainly because the sRGB space clips the CMYK gamut quite severely and you will never achieve more than 75–85% cyan in your CMYK separations.
ColorMatch RGB
ColorMatch is an open-standard RGB display space that was once implemented by Radius, who used to make displays and graphics cards for the Macintosh computer market. ColorMatch has a gamma of 1.8 and is still favored by some Macintosh users as their preferred RGB working space. Although not much larger than the gamut of a typical display space, it is at least a known standard and more compatible with legacy 1.8 gamma Macintosh files. The problem with selecting a small gamut space like this is illustrated in Figure 12.7, where, as you can see, the constraints of a ‘displayoriented’ RGB edit space can mean you end up losing tonal separation in colors that may be important, such as when carrying out an RGB to CMYK conversion.
Adobe RGB (1998)
Adobe RGB (1998) has become established as a recommended RGB editing space for RGB files that are destined to be converted to CMYK. For example, the Photoshop prepress color settings all use Adobe RGB as the default RGB working space. Adobe RGB was initially labeled as SMPTE-240M, which was a color gamut once proposed for HDTV production. As it happens, the coordinates Adobe used did not exactly match the actual SMPTE- 240M specification. Nevertheless, it proved popular as an editing space for repro work and soon became known as Adobe RGB (1998). I have in the past used Adobe RGB as my preferred RGB working space, since it is well suited for RGB to CMYK color conversions.
ProPhoto RGB
This is a large gamut RGB space that has the advantage of preserving the full gamut of raw capture files when converting the raw data to RGB. It is also suited for image editing that is intended for output to photographic materials such as transparency emulsion or a photo quality inkjet printer. This is because the gamut of ProPhoto RGB extends more into the shadow areas compared with most other RGB spaces, resulting in better tonal separation in the shadow tones.
Profiling the display
To get color management to work in Photoshop you have to calibrate and profile the computer display. This is by far the most important and essential first link in the color management chain. You can live without