Color Space: Fact and Fiction
Many photographers choose a color space arbitrarily or on a single piece of advice such as “Adobe RGB is better.” However, this shotgun approach to thinking about color space can lead to some problems when going to print or posting to the web. There are specific applications for using each color space. This post will serve as a quick guide for when to use the most common color spaces. No boring color theory here! Just the quick-and-dirty facts.
CMYK vs. RGB
First things first. The most common misconception concerns CMYK versus RGB. There are myriad sources on the internet and elsewhere which state that RGB is for web use and CMYK is for print. While partly true, this idea is an over-simplification of the concept. The problem is with the conclusion that people draw from this statement. Here is the logic:
RGB is for web – True.
CMYK is for printing – True.
CMYK is not for web – True.
The logic is good so far. The problem is in the next conclusion:
RGB is not for printing – False.
The truth is that CMYK is for offset printing only. Almost any other printing requires an RGB profile for accurate rendering of the color. Digital photographic printing (wet process, light sensitive paper) and most inkjet printing use the RGB color space. This is confusing because inkjet printers actually use cyan, magenta, yellow and black inks to create the image on the page. Even though it seems illogical, most printers need an RGB input. The specs can vary from printer to printer, so when in doubt it's a good idea to check with the package software, the manufacturer, or the photo lab.
A good image can be made off an inkjet printer with a CMYK profile, but the printer has to convert the image back to RGB before printing. The resulting quality of this transition will vary depending on the image processing software. Photoshop, for instance, does a really good job printing from various color spaces. However, with a digital photographic print made at a lab, the results will most likely be terrible from a CMYK file (unless a friendly lab worker catches it and converts the color profile for the customer – which we try to do at Pro Photo Supply’s Lab.) Wet-process printers typically have a hard time converting CMYK images to RGB, and the image ends up either being completely unprintable or just looking terrible.
sRGB vs. Adobe RGB
The sRGB color space has some PR problems. It gets a bad rap. The convention is that “Adobe RGB is better.” While that can be true, it is only true in some contexts. What people mean is that Adobe RGB gives a printer more colors to work with, also known as a wider color gamut. Is a wider color gamut always better?
There are some very good reasons to use sRBG for printing. Printing on wet-process photographic paper is a perfect example. The sRGB color space is a very accurate representation of the color gamut of this type of paper. Therefore using sRGB for the color space gives more accurate translation from the screen to the print, assuming the monitor is profiled, and the printer is giving an accurate output. If an image is in Adobe RGB, then the machine has to interpret the colors that are out of range and replace them with colors that are within the color gamut of the paper. This can lead to a significant difference between the screen and the print.
Additionally, there are times when using the sRGB color space can be beneficial for an image even when printing inkjet, which uses more colors than photographic printing does. This may not be intuitive, but sometimes Adobe RGB gives a print too many colors. For instance, skin tones do not benefit from the brighter reds that the Adobe RGB color profile will produce. Any flaw in the skin will pop out in a very unflattering way. Similarly, sepia toned images can look terrible when the color is done in Adobe RGB. The highlights and shadows can take on a strange color cast. SRGB is better for these printing scenarios. Additionally, sRGB translates better between the web and printing which makes this color space good for multiple uses.
Here are some good guidelines for choosing a color space:
sRGB – photographic process, flattering skin tones, toned black and white prints, web use.
Adobe RGB – brightly colored birds, fish, or flowers (inkjet printing is best for these punchy colors), saturated images, landscapes.
The rule of thumb should be, “Use sRGB unless there’s a reason not to.” Most devices can use sRGB, and any other color space should only be used for a specific purpose or for a specific device. Using sRGB is a very safe bet, and should be standard. That’s why it’s called sRGB. The “s” is for standard.