Monday, May 11, 2009

Color Spaces 101: CMYK, LAB, RGB, sRGB

The following overview of color spaces (aka "working spaces" or "color modes") promises to be opinionated, relatively simple, and focused specifically on digital photography for the web and most standard print labs. If you don't know what a color space is or how to use one, this primer is a must-read that will help you get better photos.

Getting good color in digital photography is a headache. When I first switched to digital, I bought a decent printer (back in the days of the Epson 2200), got some nice Hahnemühle paper, and printed...the ugliest magenta photo you have ever seen! The horror! I had no idea what I was doing. Between the monitor color settings and the Photoshop settings, I could have spent a week trying out each combination. Actually, I think I did. Worse still, I had the same problem with my local lab. The prints usually had a color cast and were far less vibrant than on my monitor.

Color calibration felt overwhelming and expensive (it has become more affordable since that time). The fact is, most average consumers will never calibrate their monitors. This means that what you see on screen will probably not be what you get in print. The good news (at least in my experience with Macs) is that monitors are better right out of the box than they used to be.

It's a safe bet that most of my readers fall into one of the following categories:
  1. You have already calibrated your monitor and you have your own strong opinions about color spaces.
  2. You have not calibrated your monitor and will not do so even if I tell you that it's really important.
  3. You have not calibrated your monitor, but based on this post you will now try it out.
I am not going to flatter myself by believing that category #3 will be greater than category #2, so I will go ahead and point those in group three (lovingly, of course) to the following sites:
But enough of calibration, let's move on to the real topic of this post: your choice of color space.

For most people—and I warned you that this post will be opinionated and simple—here is what you need to know:

Not to be confused with YKK. The letters stand for cyan, magenta, yellow, and key (which is black). CMYK is the color model used in four-color printing presses. It is called a "subtractive" color space because it assumes that your background (i.e. paper) is white and that the ink subtracts from white as it is applied. If you have an inkjet printer, you know all about buying expensive cyan, magenta, yellow, and black cartridges. So, if your printer uses those colors, it stands to reason that CMYK would be your color space of choice, right? But no! That would be too simple. We are going to buy the ink, but not the color space. We are done with you, CMYK. Nice knowing ya. Bye now. Buh-bye.

The most amazing color space you will probably never use. Until Dan Margulis wrote a ground-breaking book on LAB ("L" is for "lightness," and the "a" and "b" are for...uh..."a" and "b"), even most pros didn't bother with the strange color space. For one thing, LAB has "imaginary colors" that fall outside the realms of human vision. So, unless you have contact with a superior life form and its superior printing technology, LAB is "cool" in a nerdy mathematical way, but it is not relevant to your vacation photos. If you like theory and you want to take your Photoshop to the outer limits, LAB is for you (seriously, buy Margulis' mind-blowing book). If not, we mortals bid you adieu, oh great and mysterious color space.

This is an "additive color space," as in, Here are three colors: red, green, and blue. Add them together to make all the colors. While CMYK was "subtracting" from white, RGB is "adding" colored light to black. Imagine, for example, one of those old projectors with the big red, green, and blue circles (not that the new ones don't use RGB as well) that shows movies by sending colored light into a dark room. RGB is common in most electronic image devices, and most people love RGB because it can produce a wide color gamut without going into that whole "imaginary color" thing that makes LAB so trippy. Many of the first Photoshop books I read turned me into an RGB snob, but guess what? I stopped using it. Mostly. It's not practical for my own real-world use, so I don't recommend it. I promise to explain myself later.


The RGB snobs hate this flavor of RGB—oh, yes, there are several flavors of RGB, just to make things complicated. sRGB has the most limited color gamut of all. Does the "s," therefore, stand for it sucks ? I don't know. Blame it all on Microsoft and HP, because they created the sub-par color space. Let me skip the color theory side of things, and get to the two major reasons why I recommend sRGB:
  1. sRGB is the standard default of the internet
  2. sRGB is the color space used by most labs
Therefore, if you post photos on the web and/or have your photos printed at labs, sRGB mode will give you better results.

Remember my story about dull prints with color casts? The reason they didn't look right is that I had my camera (and Photoshop) set to Adobe RGB, but my lab was printing in sRGB. Colors that looked great in the wider gamut of Adobe RGB could not be reproduced in sRGB—Bless its inadequate little soul. Consequently, the sRGB lab printers just toned down all those great vibrant colors, leaving me disillusioned with prints from digital files.

If you do your own printing (as I sometimes do), you can take advantage of RGB and its glorious wider gamut. Otherwise, read Smugmug's convincing account of why you should choose sRGB.

Look at the settings for your digital camera. If you can choose a color space, choose sRGB (unless you do all of your own printing). Look at your color settings in Photoshop. Make the default space sRGB. Do not make the mistake of doing everything in RGB and then converting it to sRGB. Let me quote Smugmug on that topic:
"Sometimes it's written that the best workflow is to save your photos in Adobe RGB because it preserves the most colors, and convert to sRGB for the Internet.

The problem with that is you get the disadvantages of both color spaces with the advantages of neither."

This is not yet a complete solution to proper calibration, but it's a good start that will help you understand steps best saved for a future post.


grace said...

CMYK is a set of color that us in printing four color.

best lab said...

Great thoughts you got there, believe I may possibly try just some of it throughout my daily life...

calibration lab