Color Management Basics

» Posted on June 22 2009 in Calibration

One of the more complicated issues that come up when dealing with digital photography is color management. Color management is all about trying to get the colors that you want, to display properly on a given device, such as a print made on a desktop printer, or a print you get back from the photo lab, or even just on your monitor. By “devices” we mean anything that can record, display or print an image… so cameras, scanners, printers, monitors, and even papers and inks all need to be “managed” so that you get consistent color. You might find that color to not be what you want it to be, but the first step is to at least be able to consistently get the same color.

Monitor Calibration, Color Spaces, Working Spaces and Profiles

These three words are the main building blocks of color management, and basically all refer to the same thing - a color space. A color space is basically the amount of color that is contained in something… all devices are capable of different colors ie - none of them are the same really… monitors, cameras, printers… they don’t all reproduce colors in the same way. So you need something to be able to refer to the colors they can produce, and that is basically a color space. So a cell phone with a little camera in it can produce some colors, but probably not as much as the latest pro digital camera. Same with printers - a cheap color printer won’t reproduce color as well as a $200,000 laser printer in a photo lab. But knowing which device can produce which colors will allow you to get consistent color.

Monitor Calibration

Every monitor displays color different - even 2 monitors from the same manufacturer will probably show a slight difference… and then on top of that, monitors usually have color, brightness and contrast controls that you can play with… well, given all that, how do you know what is neutral? what is correct, and what is being biased by the controls being too bright, or the monitor not displaying colors correctly? Unless you calibrate it you won’t know. Calibration (we’ll stick with hardware calibration as that is the only way to go really) refers to using a device that sticks to the front of the monitor and reads the light coming through it - the little device looks sort of like a hockey puck sometimes, so people sometimes refer to it as a “puck”. The software that comes with the puck will display different colors on the monitor, and the the puck will read them. The software will then compare what the puck read on the monitor compared to what the software displayed, and figure out the difference, or calibrate it. Then the software can say, well, I sent the monitor black, but it really read it as dark gray. Or the monitor was supposed to display red, but it was really magenta. Now the software will attempt to guide you through adjusting the color, brightness and contrast of the monitor to get as close to neutral as possible. What ever cannot be accomplished with the monitor controls will be built into a profile, which your graphics card will use to try and display colors more accurately.

Color Spaces

A “color space” refers to any set of colors that a device can display or record… so in effect, every device has a color space, and most of them are unique. That said, when you hear “color space” most of the time people are talking about defined color spaces - there are several well known, well defined color spaces that are used as general default color spaces - in other words we convert whatever came out of the camera or scanner into one of these default color spaces so that we can use them across a range of devices and keep things simple. This way I can send a file to a friend and he can open it on his computer and not need to worry about whatever unique color space my camera happens to be capable of. The two most popular color spaces are Adobe 98 and sRGB. Must pro level cameras will allow you to set the color space the camera will shoot in to either Adobe 98 or sRGB. There is quite a large difference in the two, and selecting which one you use can be fairly important.

Profiles

A color profile is a complex description (using all kinds of voodoo magic) of a color space - this profile is used to tell devices how to interpret the colors. So if we were to send a digital file to a friend and say - here is that image, the color space it is in is xyzzzyzx, your friend won’t be able to view it properly unless he has the profile for xyzzzyzx - that is what will allow his monitor or printer to display it properly. This is also why we use Adobe 98 and sRGB so much - convert the image to one of those, and then you can share it with pretty much anyone as those two color spaces are pretty much available in every image editing program. Profiles can be very important when printing something - generally you will want the color profile for the printer and paper combination you will be using. If you are sending images to a lab, you probably should stick with sRGB unless they tell you differently. Most traditional chemical based printers are closest to sRGB. Building a printer profile usually is done by printing out a target print specified by the profile software, and then reading that print with a device that measures the colors - very much like calibrating a monitor. Then the software compares the colors read from the print to what were in the target file, and builds a profile based on how the two compare.

Default Working Space

Photoshop and Lightroom both have default working spaces that you can set under preferences. Lightroom is set to ProPhotoRGB by default. Which color space should you use? There have been lots of different things written about this, and basically there is no correct one - it all depends on your needs, and to a certain extent your skills. sRGB is the smallest color space - it is less capable of displaying certain colors than either Adobe 98 or ProPhoto RGB. That is not to say that the colors in sRGB look bad - it just cannot reproduce certain colors. My guess is that the average person would never notice anything wrong with an sRGB image. Adobe 98 is a much bigger space than sRGB, and ProPhoto RGB is even bigger. So it sounds like ProPhoto RGB should be the best one right? not so fast. sRGB has a couple things going for it…. are you going to display images on the web? if so, they need to be sRGB as almost all browsers assume images are sRGB and displays them as such - if you upload Adobe 98 images to your website, they probably will look flat, a little dark and the skin tones will look deadish. That is the biggest reason to keep things in sRGB - it is simple, and compatible with just about everything. If you choose to work in Adobe 98 or ProPhoto RGB, make sure any images that are going to the web are converted to sRGB first. Also, be aware than not all labs are color managed properly, and might have trouble with anything other than sRGB (the ePP Pro Lab is fully color managed and can handle any image with a profile, though the color space of the printer is closest to sRGB). I suppose an easy way to recommend a color space is that sRGB is the easiest and most compatible, so it is recommended for beginners… then as you learn more about color management and are comfortable working with different color spaces for different uses, Adobe 98 or ProPhoto RGB are more appropriate. Personally I use Adobe 98 and convert anything for the web to sRGB.