The whole topic of color management can get pretty dry and technical, but stick with it because there’s information here that’s useful and puts lots of other things in context.
Color management is essentially all about making sure you get the colors you expected when you capture photos, view them on a screen, edit them, display them on other screens or get them printed.
The explanation comes in two parts: ’color models’ and ‘colour spaces’.
Color models are the way colors are described and used by different devices. Digital cameras, computer monitors and software programs usually operate in the RGB (red, green, blue) color space, where colors are defined by their red, green and blue values using separate red, green and blue ‘channels’. These work together but can also be edited separately.
There are other color models. Printers use the CMYK model, where colors are separated into cyan, magenta, yellow and black (K) channels. This is because printers work on a different system, using ‘subtractive’ colors (regular image capture and display uses ‘additive’ color). A lot of color management processes are devoted to translating colors accurately between the RGB color space and CMYK for printing. Some editing processes are carried out in Lab mode, which separates colors into ‘Luminance’ and ‘a’ and ‘b’ colour channels.
Most photographic work, however, is carried out using the RGB color model, and this is where ‘color spaces’ come into play.
Different digital devices have different abilities when it comes to displaying colors. Some can display a wider range of colors – a wider color ‘gamut’ – than others.
This has led to a set of standard color spaces for manufacturers to work towards. The sRGB color space is the most common and is in fact a ‘lowest common denominator’ for cameras, computer monitors and other devices and displays. The sRGB color space can display a wide range of colors that match those we see in real life and does not restrict color rendition in any real way.
But there is a wider Adobe RGB color space that’s used by professional photographers, sometimes in photo editing and often for pictures to be used in commercial printing. The Adobe RGB color space has a wider gamut that is better suited to print production. The wider color space sounds good in principle, but it can cause more problems than it solves, because unless the display device can reproduce the Adobe RGB gamut, the colors won’t look right. This is where color management comes in, converting Adobe RGB colors into sRGB equivalents for computer displays, for example, when you’re editing images.
If you want to use an Adobe RGB image online, you need to convert it to the sRGB color space to make sure colors reproduce properly. Only a few computer monitors can display the Adobe RGB color space, so for online use you should use the ‘universal’ sRGB color space.
There are larger color spaces than Adobe RGB, such as Adobe ProPhoto RGB, for example. This is essentially a ‘working space’ not designed specifically for output, but to make sure you’re working with a color gamut wider than any color space you might need later – it gives you more processing ‘headroom’.
There is a third tier to color management: ‘device profiles’. Even though they might conform to a particular color space, such as sRGB, different devices have different color rendition or calibration. To get truly accurate colors you need device profiles which ‘correct’ the color to make it consistent with every other device in your workflow.
Computer monitors are the biggest culprits. This is why photographers use monitor calibration tools. These use a hardware device to measure the colors produced by the monitor and software to compare them to the true values to create a ‘monitor profile’ – the monitor’s colors should now be accurate.
Printers are another source of inaccuracy, especially if you use papers and inks that aren’t made by the printer manufacturer. Here, it’s common to get ready-made printer profiles from paper manufactures to correct any color shifts, though you can also get printer calibration kits to do this yourself.
Some photographers even used camera calibration profiles to correct the colors captured by the camera. In reality, though, most photographers simply accept their cameras’ rendition for what it is and correct or enhance it in software. Different RAW converters use different camera profiles anyway, so there is always some variation here.
To sum up, color management is used to achieve consistent colors in your workflow, when you will be working with a range of devices, color spaces, color models and specific device profiles.
It’s possible to produce perfectly good results without using color management at all, simply by adapting to the the properties of your different devices. Some photographers, however, prefer the consistency that color management brings, and are prepared to accept the complexity that comes with it.