Pros and Cons of working in LAB color mode

Question

I like to use LAB as my color mode. Partially becasue I have a spectrophotmeter and can sample things; partially becasue it is the space which I am most familiar with.
If you pick up almost any ID instruction book, it says "ID has three color modes: RGB, CMYK, and LAB. We aren't going to talk about LAB."  I assume that is at least partially due to legacy.  However, is there something I am overlooking? Is there a danger to work working in LAB I haven't thought through?
Mostly my work is output to web or print - both desktop and offset - without spot colors.

Answer 1

MarieMeyer wrote:
I seems to me that if I specify colors in LAB and then output to sRGB or Adobe RGB the color is going to be the same - whereas if I had typed in RGB values it will not. (Realizing this is NOT some magic cure for monitors not being calibrated!)
Obviously ID isn't an image editing/generator program, but for brochures and thing I do apply flat areas of colors. If I type in a LAB color that is out of the gamut of the CMYK profile of the working space, I get an OOG warning and can dial it back.  What I really like is the speed with which I can adjust the value of the color without changing the hue/chroma by adjusting just the L channel.  It is sort of like creating tint swatches, only in reverse!
dylw, I take your point about the number of printers who aren't meticulous. But don't I have the same problem if I'm relying on a swatchbook that provides CMYK values but was printed on a differe paper at a different company than the one that I'm going to use?
When I was a student I used to worry about exact color matching and presume that it could be achieved. Now that I've been out here working in the real world for a few years I understand that perfect color matching, even with good color management, is a myth. Most users don't have calibrated monitors, or even monitors capable of displaying the full gamut of what your eye can see or even what your camera or scanner might be able to capture, and process color gamuts are genereally smaller still. When you go to press you are at the mercy of the press operator, the vagaries of plate making equipment, paper inconsistencies, ink mixing, and even ink brand, not to mention the light sources in use at the press and in your office and where your product is finally viewed by your user, and how those particular inks react to differnt wavelengths.
Even a custom profile is at best a point sample, or an average of many point samples, from a particular run or runs, and is not going to match every sheet that comes off the press. A well-trained eye can probably spot variation in color from one end of a single press run to the other, and even more likely from one run to another. Your spectrophotometer is using a particular wavelength and angle of light to sample your color. Is that the same wavelength and angle that will be used in the client's office under the fluorescents? Has your specrophotmeter aged and drifted?
Color management is about getting good, or even excellent, matching of colors across various output conditions, but there are too many environmental variables to be able to achieve one single "perfect" set of output numbers. All you have to do is grab some output and stand in a doorway and compare what you see in daylight against what you see in room light to demonstrate. The human eye and brain, to varying degrees, recognize certain things as being "normal" colors and will accomodate to tell us, for example, that paper is white, even if it's a bit yellow or gray, until we have a whiter sample for comparison. Further, most of us are incapable of seeing the difference a 1 or 2% density shift on press would produce (and that's pretty close to the tolerance you could hope to achieve in the pressroom), let alone the fractions of percents that we often specify when converting colors.
Lab is a theoretical color space that has no "real world" equivalent, but is extremely useful for translating colors from one real world condition to another. Even if you choose to work "in" Lab, you are at best translating your sampled colors under their specific sampling conditions (which don't match your general lighting) to your monitor space (which may or may not be accurate) and then asking to translate to yet one more output space that probably will not match the real world conditions under which the finished work will be viewed.
What you are doing by specifying the color in Lab is trying to eliminate the source profile, but I doubt you'll get any better output.