|| SportsShooter.com: News Item: Posted 2004-03-03
Pushing Pixels: Color Spaces or, 'What does Adobe RGB and sRGB mean anyway?'
By Reed Hoffmann, Blue Pixel
I received an email from Billy Suratt asking about Adobe RGB vs. sRGB:
I've been debating the whole Adobe RGB (1998) vs. sRGB thing with a buddy and I'm at a little bit of an impasse. I "know" ARGB98 is better, but I'm having trouble explaining why. Since the topic doesn't appear to have come up on Sports Shooter recently, I thought it might be a good topic for your column.
Billy's partially right when he says that he knows that Adobe RGB is "better." Let's start by talking about what color spaces are and where sRGB and Adobe RGB came from.
Color scientists think they have a pretty good handle on what range of color and tone the human visual system can "see." That's our starting point, and everything else derives from that, since there's no other device that can display or reproduce that range of color. All color spaces, then, are ranges of color and tone that fall somewhere within what the human visual system is capable of seeing. For all you sports shooter types, let's take a football field and imagine that space, from goal line to goal line and the full width of the field, as containing all the color our eyes and brains can see.
Enter software engineers and computer and printer and monitor makers, who want to figure out how to properly create and display color. They measure the range that a standard computer monitor is capable of displaying, and call that sRGB. Let's say it covers that football field from one 25-yardline to the other 25-yardline, and within about 10-yards of each sideline. Everybody's happy because now when a programmer tells the computer to display fire engine red it's close to that on the monitor, and on the printer too (if you're lucky).
Next thing you know, everybody's starting to print color, but realizing that their printers use a CMYK ink process and their monitors are RGB. And they're finding out that those CMYK printers are capable of reproducing more colors than the sRGB space is capable of holding. Time for a new color space, one that covers the range of colors that the CMYK printing process can print. Say "hello" Adobe RGB.
When the first digital cameras were being built, they produced color in their own "space," depending on what the camera manufacturer thought good color should be. Problem was, that camera color space had little meaning outside the camera. Enter color conversion, where a group of colors is converted from one space to another, trying to keep the look of the colors the same. Compact cameras settled on converting the color to the sRGB space. So did some digital SLRs, and the Nikon D1 settled on NTSC 1953.
Starting with the Nikon D1X, though, camera manufacturers started letting photographers choose the color space they wanted the camera to process that color into, in this case giving us two sRGB choices (Mode I and Mode III) and Adobe RGB (Mode II). Canon had Matrix choices in their cameras, and Matrix 4 was Adobe RGB (Canon's more recent cameras make it easier by having a choice that just says "Adobe RGB").
Now we come back to Billy's question about whether Adobe RGB is "better" than sRGB. And the answer is… it depends. Adobe RGB is a larger color space than sRGB, but that doesn't make it intrinsically better. Because of the color processing that goes on inside the camera, one camera may give a better-looking image while set to sRGB than Adobe RGB.
What's this all mean? In general, if your images are destined for print, you should probably set your cameras for Adobe RGB. Notice I said "in general" and "probably." Hedging my bets a bit, aren't I? Here's why - just because a camera can convert its images into the Adobe RGB color space doesn't mean that's the color you'll like best. Remember, a color space merely defines how wide a range of color that can be captured/reproduced. Each manufacturer is free to come up with their own vision of what proper color is. If you shoot the same scene with different brand cameras, all set to Adobe RGB, you'll get different color in those images based on how those makers have decided color should "look." This is why, for instance, you
have two different sRGB Modes in the Nikon SLRs, which can give very different looking color in some scenes.
Of course, you'll have no idea what that color really looks like unless you're sitting in front of a properly calibrated and profiled monitor, which few people are. To do that, you need to be using a fairly recent system (my favorites are the Gretag MacBeth Eye-One Display and the Monaco Optix XR). If your organization's using a system more than about three or four years old, there's a good chance it isn't creating a good profile, or even calibrating properly. Also, keep in mind that an old monitor (three years is a good guess) can't be calibrated or profiled properly.
So what's a photojournalist to do? In general, here are my recommendations:
1 - If your camera offers Adobe RGB, you should probably be using it. It's usually the right place for a photographer shooting for print. If your camera doesn't offer it, don't lose sleep. Contrary to popular playground myth, sRGB isn't a bad color space, it's just misunderstood. Perfectly good pictures can be made (and often are) in sRGB. The Canon D30 is a good example of this. It has no choice but sRGB, but turns out very nice color.
2 - Make sure that your editing software, which I'll just call Photoshop from this point on, is set with your working space the same as your camera (Adobe RGB in this case) and that your images are properly assigned Adobe RGB coming into Photoshop.
Okay, this is where things get a bit weird. Just because you've set your camera for Adobe RGB doesn't mean that Photoshop will recognize it as Adobe RGB. In fact, Photoshop may very well tell you it's sRGB, making you think the camera's broken. The camera's not broken, Photoshop's not broken. It's the communications between the two that's broken. And everyone's working on better ways of making them communicate. In the meantime, what's a photographer to do?
Here are the steps I suggest:
* Find out how your camera records that information and whether Photoshop can read it correctly or not, and then set up your workflow accordingly.
* Or… follow these steps:
- If using Photoshop 7.0, install the 7.0.1 update and then the Ignore EXIF plug-in (both available free from http://www.adobe.com .
- If using Photoshop CS, turn on the "Ignore EXIF profile tag" in the preferences.
- If using Photoshop 6, keep on keeping on.
- If using Photoshop 5 or 5.5, upgrade to 6 or later. The way Adobe handled color management in those versions may it nearly impossible to open, view and save photos without mangling the color space.
- If using Photoshop 4 or earlier, congratulations, you've gotten your money out of the software! Of course, there's no color management built in, making an upgrade mandatory if you want to do this.
Now Photoshop won't be confused by digital camera images. It just won't apply any profile to any image that it sees coming from a digital camera. Because of that, you'll want to be sure to assign the correct profile for the photo when you open it. You do that by going to Image - Mode - Assign Profile and choose the correct profile from the pull-down. Luckily, you can create an Action for this in Photoshop, so that it's a one-button push each time you open an image. If this makes you head hurt, remember, we'll all be laughing about this in a few years. At least I hope we will…
3 - When saving your image, make sure the "Embed Color Profile…" is checked with the correct color space in the bottom of the "Save" dialog.
Even if you're not working with a properly color managed computer or workflow (in newspapers it's more often color manglement), you'll go to bed each night knowing that you're doing your part of the process properly.
Keep those questions coming (firstname.lastname@example.org). and remember, as interesting as all this techie stuff is, it's the photo that really matters.
(Rob Galbraith of http://www.robgalbraith.com contributed to this story)
(Reed Hoffmann is a former newspaper photographer and now a partner in Blue Pixel, a digital photography consulting and training company. For more information about Reed and services offered by Blue Pixel, check out their web site at: http://www.bluepixel.net /)
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