Color space defines the range of colors a device or application – digital camera, printer, computer monitor, Photoshop, etc., is capable of capturing or reproducing. Generally speaking, the broader the color range, or “gamut”, the richer and more true-to-life the colors will be.
As the diagram above illustrates, color spaces function as reference points to help devices interpret the colors of an image. Colors visible to the human eye are represented by the horseshoe shape. Inside the horseshoe are color spaces displayed as various geometric shapes. Most consumer-level devices are low-gamut and can only display colors within the sRGB space.
Most Commonly Used Color Spaces
There are over a dozen color spaces available with the following three being the most commonly used:
1) Standard RGB or sRGB
Developed jointly by Hewlett-Packard and Microsoft as the default color space for consumer-level devices and for displaying images on the internet, making it a popular choice for photographers primarily displaying their photos online.
2) Adobe RGB
Developed by Adobe for creative professionals, this color space was modeled after the color reproduction capabilities of CMYK printers (the diagram above shows the SWOP CMYK color space inside Adobe RGB.) The color gamut available in Adobe RGB is quite broad and many of its hues cannot be seen or reproduced accurately without the use of high-gamut professional displays and printers (on anything less, colors will appear flat or washed out.)
3) ProPhoto RGB
Also known as ROMM RGB or Reference Output Medium Metric RGB and developed by Kodak to reproduce the entire spectrum of color visible to the human eye, ProPhoto RGB has the broadest range of all color spaces, so broad that at its boundaries a few imaginary or invisible colors are introduced. Naturally, you’ll need professional displays and printers if working in ProPhoto RGB.
Why it Matters
Broad color spaces are appealing for their ability to reproduce more of the colors we love, but they are not always practical since hardware is a limiting factor. If your primary interest is sharing or displaying images online, using the ubiquitous sRGB color space for capture and editing is just fine and will provide consistent reproduction across the widest range of devices. For professional and other color critical applications, assigning one of the broader color spaces may make sense; just remember that all devices in your workflow must be capable of exploiting the broader color space or you may be disappointed by the results.
One more thing: the RAW image format captures the complete record of color information available at the scene and does not have a fixed color space (one is assigned — usually sRGB, only when the image is converted.) If high-gamut devices one day become standard, your RAW files will give you total flexibility to assign a color space that more faithfully reproduces the colors of your original image.