Photographic Color Spaces

There are a number of “Color Spaces” or profiles available for the digital photographer. In some cases the photographer can set them in the camera; they are always available with most photo editors. Unless you are shooting RAW images with your camera, you assign a color space to the image when you take a picture. Although a RAW file does not have a color space other than the data recorded from the camera’s sensor, it is assigned one when it is converted by your post processing software. Most cameras allow the photographer a choice of two in camera profiles – Adobe RGB (aRGB) or sRGB. To explain the difference & why it should be important to you you need to understand how your camera records color.

If you are shooting JPGs, your camera is recording 8 bits or 256 possible levels of each of the three primary colors of light – Red, Green, and Blue. Theoretically, you can record 16,777,216 (256 possible Red X 256 possible Green X 256 possible Blue) values for any part of your image. Shoot 16 bit & there are 281 trillion possibilities. The problem is although there may be that many colors available, very few devices, including your camera, are capable of producing or displaying all of them, even in the 8 bit mode. Color spaces are sub sets of this total number that different devices can display. It is important to understand that as far as digital devices are concerned, there is no such thing as color – all they understand is a bunch of numbers. For example, check the two squares below. Each is the same color numberwise – R88/G249/B17. The first is the color you get using Adobe RGB, the second sRGB.

This points out why understanding color space is important if you expect to have the same color throughout the processing & printing process.

The sRGB profile is one of the smallest subsets. It was developed by HP & Microsoft as an attempt to keep colors the same as your image moves between different devices. By limiting the range of color, more devices can successfully reproduce the same results from the same numbers.

As cameras, scanners & printers improved in their ability to reproduce color, there was a desire to expand on the limited range of sRGB. Adobe developed the Adobe RGB (aRGB) color space as an improvement over the universal sRGB. Not only is it a wider space (more colors) but it can be managed. If the image has an assigned color profile, and each device the data passes through also has an assigned color profile, the data is modified to produce the best possible results within the capabilities of each device.

Since we now have at least 2 profiles (there are many more – Photoshop lists at least 50 in CS3) there can be a problem if devices or applications are not color profile (space) aware. For example, you may want to shoot your images in aRGB since it is often the widest color space available for your camera, and you want to capture as much information as possible. You take your files to the nearest drug store kiosk to make prints. For some reason, those beautiful fall colors come out muted & dull. Why? The printer assumed your images were in the sRGB color space and all that extra information went down the drain. While it is possible to use a color space designed for a particular commercial printer, most are set to expect images in the sRGB color space. Unless you use an editor to change your aRGB image to a sRGB file for printing, you may have problems with the results.

If you do your own printing, you may find your printer install disk includes a color profile for your printer as well as additional ones for each type of paper. By using the correct profile you will get the best result from your image. Dry Creek Photo has created profiles for Fuji Frontier and Noritsu digital printers, the type used at Costcos, Walmarts, and many drug stores. They include specific profiles for individual printers at many locations throughout the US & describe the process of using these profiles here.

Most operating systems provide a general profile for your monitor. You can purchase a hardware device such as the ColorVision Spyder to more accurately calibrate your monitor if exact color matching is important to you. Although this may be a bit overboard for the average picture taker, by calibrating all the pieces of your equipment you can end up with the same color throughout the picture making process.

Unfortunately, most internet browsers are not color space aware. You can test your browser at the International Color Consortium’s Browser Test Page. Using your browser, go to their page. Look at the image of the mountain & the sample results shown below the image. Safari is color profile aware. Firefox 4 can be if you go to preferences & turn it on. Otherwise, most browsers are not color aware. It is important for anyone posting images to use the sRGB color space. If you don’t, your images may look great on your color aware browser, but dull & lifeless on those used by most of your viewers. This is of particular importance to Macintosh users that use Safari as their browser or anyone posting directly out of their image editor.

One additional color space that is worth mentioning is Pro Photo RGB, developed by Kodak. This is a wider space than Adobe RGB, and much wider than sRGB. Although I don’t know of any cameras that can directly shoot Pro Photo RGB, if you shoot RAW you may be able to choose Pro Photo RGB as your working or output color space. Many editors such as Lightroom & Photoshop use the Pro Photo RGB color space internally. Because the color space includes so many colors (90% of what is available) it is recommended that all editing be done in 16 bit rather than 8 bit to prevent color banding. Although this is the widest color space available, your output device must be aware of the profile for it to properly handle your image. Again, if you are posting to a web page, it is wise to convert any Adobe RGB or Pro Photo RGB to sRGB, otherwise most of your viewers will not see what you expect them to see.