2006-04-08
I don't have any figures, so I'll just make some up: hundreds of thousands of Mac users buy photo-quality printers so they can print their own photos, and 95% of them print from iPhoto (which comes free with every Mac).
(What I'm going to say here about the Mac applies to Windows and Linux, too, except that there's no photo cataloging/editing/printing application that's as dominant on those systems as iPhoto is on the Mac.)
Just pretend for a few minutes that these figures are right. If they're wrong, they're close enough for me to make my point.
Any image file, most often a JPEG, encodes colors as numbers. They're compressed in the JPEG, but what they really are is 24-bit numbers, with 8-bits for red, green, and blue. (That's where the letters RGB come from.) A color might be something like (103,202,197). This means, for the red component, 103 on a scale of 0 to 255. How red is that? If you've ever seen a wall of TVs in an electronics store, you know that a given amount of red (or green or blue) is interpreted differently by different TVs. The colors vary a lot from TV to TV.
The same variation occurs for monitors and printers. That 103 looks like one red on your monitor, and like another red on mine. If you print the picture, the 103 will be something different on your printer than it was on your monitor. Same for my printer.
Now, if you don't care about that, you should consider yourself lucky, because for you everything is OK. You can use iPhoto with your printer, any printer, and you'll be happy.
But, what if you care about how red looks on the print? Maybe it's not the red all by itself you care about, but flesh tones, for which red is only one of the components.
If you do care about how red (or green or blue) looks on the print, you need that 103 to be compared to a standard so you'll know exactly how far off it is. Same for the other colors, too. The whole set of comparisons to the standard are called a color profile. You need one profile for your monitor, and another, different one for your printer. Wait... it's worse: For your printer, you need a different profile for each kind of paper (e.g., glossy, matte).
Given a set of numbers and a color profile for a device, software can convert the numbers to whatever they need to be to make the colors come out right on that device. That conversion is part of what's called color management. Color management converts the 103 in the image to whatever it needs to be to show the corresponding standard color on your monitor, and a similar conversion occurs when you print.
You also need to calibrate your monitor against a standard before the monitor's color profile is generated, so it's as close as possible to the standard, but we don't need to get into calibration, except to say that the only way to do it is with a hardware calibration device. Let's just for the purposes of this little essay say that you've somehow already done that.
With color management and the two profiles, when you edit the photo to adjust the color, you're adjusting it against a known standard. If you get it to where it looks right on your monitor, and then, using the printer's color profile, convert the 103 (and all the other numbers) to whatever they have to be for the printer, the colors on the print will match what you saw on the screen. (Actually, they'll match only as well as the printer can match them, since printers can't show as wide a range of colors as monitors can.)
Even if you didn't follow my whole explanation, at least you now know that to edit and print a photograph you need:
- Your monitor calibrated with a hardware calibration device,
- A color profile for your monitor,
- A color profile for your printer and paper, and
- Printing software that does color management.
Really! I'm not kidding! You can't print accurate colors without all four of those things!
Now, what percentage of the people who print photos use hardware calibrators on their monitors? I think 0.1% is high, but I'm only guessing. What percentage have monitor profiles? Ah... that's a trick question, because Macs (and Windows computers, too), always use some profile. But, if the monitor isn't calibrated, that profile is useless. And, the number of iPhoto users who use a printer profile when they print is zero, because iPhoto doesn't manage color.
(You might think that you can calibrate your monitor and generate a profile with one of those software-only adjustment utilities, but, if you have an LCD, they won't work at all. They don't tell you that.)
Well, this is the part of my blog entry when I need to come to the point. So, what is my point? Oh yeah... just remembered: My point is that since color profiles and color management are too hard to explain, and I'm sure I didn't explain them very well, and since hardly anyone has a hardware calibrator, or even knows what one is, they just skip the whole thing. No wonder iPhoto is so easy to use!
A long time ago, cars were a lot harder to drive. Electric starters came along, then automatic transmissions, then power steering and brakes. Where's the automatic transmisison for editing and printing photos?