How Come my Photos are all Magenta?

or Solving The Mystery of Color Profiles
© 2003 Tracy Valleau

So: your photo prints are not matching what you see on screen, eh.... by a LOT... eh? Well, there are a number of possible reasons, but if you're just getting started there's a 99% chance that it's "mismatched profiles."

I wrote this years ago, when it really -wasnews, but as new folks take up digital photography, and have their early experiences trying to print from Photoshop, the fact remains that, er... these facts remain! :)

It's all about "ColorSync" and color spaces. *

The problem with ColorSync and color spaces is that no one ever bothered to explain it clearly, and thus, most folks either end up with prints that bear little color resemblance to what they see on the screen, or just end up giving up.

Let's see if I can clear this up a bit.

First what color matching (and "ColorSync" is Apple's name for the tools that help with that process) is fairly simple. (Where it gets confusing is the range of options, but let's look at it clearly, and just consider how to get a generally good color print...)

Let's take scanners first. Even if you don't have a scanner, this is the best example for explanation of the process.

You can buy prints (usually at photo or art stores) that have a known color value, such as 100% cyan or 100% yellow. In fact, those target prints are much more complex, and have hundreds of known-value color swatches on them.

Let's say that the top (just to keep it simple) has a magenta of value 90 (M90) and a cyan of value 86 (C86).

Now you scan that in, and using the calibration software (yes, you need another program) looks at those two and sees M 92 and C 80. Well, now it's simple. It just makes a report that says "Scanner x needs to adjust M90 by -2 and C86 by by +6."

That's a color profile.

Now what we want is a color profile for each device in the work-chain.

The monitor is next.

You can either create the profile by eye (using Apple's built-in "colors" choice in the monitor's preferences) or by using a hardwdare/software combination that reads the output of the screen directly. These can be had from a few hundred dollars up to thousands (of course ;)

Once you have a profile for your monitor, you have to leave your monitor alone: no more adjusting brightness, contrast, or, of course, color... unless you make a new profile for that setting. Now, monitors are unique in the chain. For one thing, the profile you select is used "transparently" by the software you're running (we'll be discussing Photoshop here). That is, other than the monitor preferences, there's no place you tell your software which profile is used it just uses the currently selected one.

Next, monitors are "two way" devices. You can set up a profile for a different color setting (say gamma 1.18 vs 2.2 (yes, I'll explain) and when you switch between the two, the screen will change as well.

Now this is, admittedly, iffy, since your setting of the contrast and brightness are manual settings on the monitor itself, and the profile has no way of knowing if they have changed. Thus, the usual advice of set-it-and-forget-it.

(Gamma, btw, is just the range of the mid-tones. Try using the monitor preferences to adjust your monitor (you don't have to save the results) and get to the screen where the gamma is set. Watch the sample picture as you make changes, and it's pretty obvious what's happening.)

Then, there's the printer. Printers are the hardest of the lot, since the output is a piece of paper, and not something digital. In fact, to really calibrate (get a profile for) a printer, you need a very expensive piece of equipment called a spectrometer, costing $2000$4000. Let's assume we're not all going to rush out and buy one.

But before we figure out the poor-man's solution, let's make sure we understand what it is and why we need it... and it's the same as the scanner and the monitor.

A spectrometer simply reads the printed page and says "well, that M90 printed as M87, and that C86 printed out as C93, so we need to adjust the output by M+3 and C-7."

Simple enough.

Now, if you think about it, you'd say that the kind of reading you'd get depends a lot on the kind of ink, and the kind of paper as well... some is really reflective, and some absorbs a lot of ink and so on.

And that's exactly what the printer manufacturer did. They did the expensive tests, and include in their software, when you buy the printer, profiles for their various inks and papers. And those are generally pretty close. You may well be happy with them.

The most expensive spectrometer is also the most accurate: the human eye. You can, of course, just look at the output and say "well, that's way too yellow" and make some tweaks by hand in the printer output dialog box (since creating a colorsync profile by hand is way beyond the range of this little discussion).

Finally, a couple of you bright bulbs out there have also already realized that our perfectly calibrated scanner is, in essence, a spectrometer, since it reads printed pages... and yes, there is, or used to be, software that would use your scanner to help set up profiles for your printer. (I'll look around...)

So, there we are... almost.

The basic idea is simple: this device is off by + this and that, and device 2 is off by some other this and that...and so on. As long as the devices read the profiles, and make the corrections, we should get pretty much the same thing in a print as we saw on the screen, or scanned in. ("Pretty much" because this is, after all, the real world, and everything needs a bit of tweaking...) But you get the idea.

" Almost..." because we now need to consider the great pot into which all this is dumped, stirred, candied and spewed forth for printing: Photoshop.

Photoshop is really the same idea, but with a bit more complexity.

Ready? Here we go...

It probably won't surprise you to learn that those photos you take have a profile embedded in them by the camera itself. Some of these contain miniscule amounts of useless information (as far as we're concerned in this discussion) and others have a wealth of it. And, since this is the wonderful world of computers, naturally there are half-a-dozen competing formats for these profiles.

Some manufacturers (Canon comes to mind) have even marketed printers that read these profiles and make pretty darned good prints (although usually no bigger than 4x6). Other manufactures of printers have landed on one or another of the competing profiles, and announced support for them.

Photoshop, on the other hand, has to be able to do darned near anything.

And, this is the digital world as in "numbers." Yep: that photo you're looking at is just a bunch of numbers, being interpreted to display on your screen, or be sent to a printer. Most of you will remember that those numbers usually run between 0 and 255. That is, 256 shades of red; 256 shades of green; 256 shades of blue. 256 x 256 x 256 = about 16 million shades of color... far more than the human eye can discriminate. (OK, we'll save this for a later discussion, but the key to understanding Photoshop is that it's not RGB (Red Green Blue) really: it's 3 instances of 0-255 grays...)

OK. Fine. 256. Numbers. So?

Well, there's one bit missing from all this: the _range_ of color that is represented by those 256 numbers. Is 0 soft red? faint red? pink? Is 255 BRIGHT red? Dark red? Red so dark it's black? You see? Photoshop needs to know the range of colors represented by those 0-255 numbers... the "gamut" of the color; its range.

Aha! This is beginning to make some sense. Photoshop calls that color gamut "a workspace". You have to tell Photoshop what the workspace is supposed to represent before you can expect it to make appropriate changes to your adjustments.

There are a bunch of gamut options for RGB (projected (or "additive" light, like your monitor) and CMYK (reflected or "subtractive" light, like a photograph). There is a gamut for grayscale too.

Now, here's what that means to you.

You need to tell Photoshop which gamut to use for your on-screen work. Remember, we're trying to get what you see on your print to match what you see on the computer screen. (Also, remember I'm trying to keep this simple, because there are a lot of variations that I could discuss which would only muddy things right now.)

So: let's tell Photoshop that we want it to use the widest possible range of RGB colors. Makes sense, if we're trying to deal with photos, no? OK: that widest RGB gamut is called Adobe RBG (1998). **

Go the the Photoshop color settings; select the "workspace" section and for RGB, choose Adobe RGB. What you'd doing here is telling PS that when it opens a picture, it should convert what it sees there into the Adobe RGB working space.

The next item is telling it what to do if the image it opens isn't an RGB file, buy a CMYK (print) file. Well, your camera takes RGB photos, so this isn't really important for this discussion, so just leave it at "generic".

Finally, if the photo it opens is grayscale, you should probably set it for gamma 2.2. (But, later: we're concerned with your color photos here.)

Next we come to a part which is just for your convenience. Tell PS what you want to have happen, given those settings above, when you open a document. Do you want it to automatically make the conversion, or to stop and ask you? That's what "color management" does.

I've decided that I really want all my photos converted to the working space (which I set above to Adobe RGB (1998)) so I'm going to check the box that says to convert it without asking. If I ever work with CMYK I'm gonna assume that file is right already, so I selecting "preserve" for CMYK.

Gray: heck a really gray-scale digital camera setting has more than 256 shades of gray, so I don't want to mess with that at all... leave it off.

And for anything else: stop and ask me.

Next, we come to "conversion options"... we're gonna convert to Adobe RGB (1998)... but how?

There are several sets of different rules on how this is done. Fortunately, I can just tell you one to stick with until you have reason to change: pick ACE (Adobe Conversion Engine). It's good; it's used by all the other Adobe products; and it will be working with Adobe RGB anyhow. For intent: choose "perceptual" for most photos. (Yes, yes yes... there's a lot more to this, but for now just do it.)

Use black-point compensation. Dunna make any difference how it's set if you selected perceptual, since perceptual ignores this setting. Use dither. Sure. Leave it on. Just because I said so. (OK: because it will give you less of a Peter Maxx look...)

You're finally done telling Photoshop what it needs to know to work with your image.

Whew!

But, of course, you're not done... ... assuming you'd actually like to print this little puppy. It's print time, and the end of the tunnel is in sight.

There's two things left: tell Photoshop what to output and then tell your printer driver (which is NOT part of Photoshop) how to print it.

If you're just been hitting "print" instead of "print preview" you've been doing it wrong. Choose print preview from the file menu. Twirl down the triangle by "advanced" at the bottom left. The document should be set to Adobe RGB already. Now you want to choose the print space.

Aha! Yep: just like there is a work space in PS, there's a printer space for the printer.

Here you can choose one of two options really: either the profile that is recommended for your printer/ink/paper (it's usually listed as a paper type) or try letting the printer handle it alone. If you're using the printer/paper profile (supplied by the manufacturer, or done by you with that $3000 spectrometer) then it will likely look like "Epson Stylus 880 Glossy Photo Paper" or "7600 PrmGlossy PGL2Std v3.icc" or some such thing.

If you don't have those profiles (or even if you do and you just want to try this instead) let's let the printer drivers handle it, and select here at the top (second from the top for me) of the pop-up menu: Postscript color management. (Some may see it listed as "Printer color management".) We're simply saying: let the printer do this, thank you very much.

Check to see that the intent is set to perceptual, since that's what you told Photoshop you were doing... ...and hit the print button.

NOW -Last Step! (Whee!) Now you're looking at the printer driver that came with your printer. Having gone thru all this, the VERY LAST THING we'd ever want to do is tell this driver to muck about with our carefully adjusted file. So DON'T CHOOSE ANY color management in the set up here. If you're using a printer/paper profile, then turn color management OFF! (That will be under the Color Management settings, in the pop-up menu.) DON'T turn on "Epson Natural color".

If you chose "Postscript color management" (instead of a printer/paper profile in the print preview box) you should probably leave the Printer settings pop-up set to automatic, or go to color management and turn it off. Try one of each to see which looks better.

However, with either selection, DO BE SURE to select the kind of paper you're printing on! (And if you chose a paper profile in the print preview box, above, be sure that you choose that kind of paper here. No cheating.)

We're done! Really. Hit "print".

If you did all those steps: calibrate your monitor and then don't change it; tell Photoshop what your work and print spaces are; and tell printer what to do, and not do, then your print ought to look darned close to what you say on screen.

If you find that your printer is always slightly yellow, or a niblet too magenta on a regular basis, you can use the printer driver's color adjustment section (violating my rule about not mucking about with the settings, but this is, we noted earlier, the real world.) Fortunately, you can also save your settings, with whatever name you choose, so this should be a one-time affair...

Final tip: make little tiny strips of a photo that shows human flesh. We're all pretty good at reading skin-tones, and using this, and making it small, so you can use that same piece of paper more than once (by trimming it) will help you tweak you output without eating up lots of expensive photo paper in the process.

OK the final, final tip, for you newbies to printing photos. To get those prints that really look like photos (you know, the ones you saw in the ad for your shiney new printer?) do this: In Photoshop, select Image Size. UNCHECK the box that says "resample image". Now start changing the resolution (in pixels/inch) upwards until you get the photosize you want printed out. (Bear in mind that for a good print from a 2 or three megapixel camera this will be about 4 x 6 inches or so.) Then hit OK. You won't see much change on the screen, but the print will look just fine now.

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* Actually, I've oversimplied this greatly. There is, for example, actually an intermediary target profile to which everything is calibrated, so that rather than just a chain of adjustments, it's really more like a wagon wheel, where the ends of the spokes are all adjusted against the single value at the "hub"... and so on. The point of this give you the general jist of things; not a technical explanation.

** The widest often used range is called ProRGB, but there are no printers that can use it. (Yeah, and for you sticklers...the real widest range is Lab...)