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 p.1 #11 · Affordable printer color mgmt | |
The axiom of "If you can see the difference it matters" applies to color management.
First you need to understand that no printer will be an exact match to your screen; the gamuts are different. The goal is for the images you display on screen and print to match your impression of the scene in person with similar tonal range and detail, things you expect to be neutral neutral on screen and print, etc.
If you stick to the manufacturer's papers and profiles if you record an image of a person holding a Macbeth chart the person and chart, while not an exact match to screen and print, will be be close enough for non-critical applications like scenics and portraits where the exact color of things isn't that critical. Keeping the neutrals free of color biases is more critical because you expect a tire on a car to look neutral black, not have a color cast.
An example of critical color balance would be an advertising poster of a red car that will hang in the showroom over the car for comparison or a photo in a catalog a buyer will use to make color selections. For less critical subjects if the neutrals are correct an there is a full tonal range the fact an apple in a photo isn't an exact match to the one on the tree won't be noticed because apples come in a range of color variations.
The more the process control is front loaded the easier and more automatic the other steps in the color management workflow will be.
I always set custom WB off a gray card when possible and include the card in test shots. That way I don't have to adjust color when editing, other than to intentionally skew it warmer / cooler to evoke mood. With a calibrated monitor the results out of camera look as good as the calibrated monitor can make them. When I print the file straight out of camera the printer profile should, if everything is working correctly, map the gamut of the editing space (e.g. ProPhoto RGB) to the printer's gamut per the paper/ink profile and figure out what combination of CYMK ink is needed to make the tires on the car neutral black.
If you start with a file that doesn't have "by the numbers" R=G=B on a gray card in the image for reference and adjust color visually based on your perception of color on the content on the monitor its a bit like whacking at a Pinata blindfolded because of the way color vision adapts. Here's an example:
With a camera set on Daylight WB you shoot under trees in the woods. The trees are reflecting green light off the leaves making the light on the white shirt of your subject green. But your eyes have adjusted and it looks white. You take a shot and chimp. The shirt is actually green in the photo on the playback but because your eyes are adapted to the ambient it will look neutral. You will not see the color bias problem.
You get home and open the file on the computer. Your brain knows the shirt should be white and that you used the "correct" daylight WB. What happens? Your brain will adapt color perception of the screen image + magenta so the shirt looks white. Your monitor may be calibrated to a constant baseline but your brain isn't.
If your subject was holding a gray card in the photo and you click corrected on it the color balance of the monitor would shift + magenta to remove the green bias. Now your brain, knowing how the eyedropper tool works trusts that second version more than the first. If you toggle back and forth from out of camera to gray card corrected you'll see the obvious green cast in the as taken from the baseline of believing the correction being more accurate.
You can do the same thing in the field. I always set the camera to Daylight outdoors before setting custom WB. Then I shoot the card with Daylight WB, set Custom WB and then shoot it again. Toggling back and forth between Daylight and Custom WB renderings of the card I can see if the actual lighting matches daylight or has a color cast. If done under trees the Daylight shot will look green compared to the Custom WB shot of the card.
What happens if you printed the out of camera shot with Daylight WB and the green tint you don't see in the playback or computer? The printer prints will reproduce the card per the file values and it will be green on the print. It will likely be noticed more than on screen if the print is seen around other neutral objects for reference.
All of that has nothing to do with the technology of the camera > screen > printer color management but you need to be aware of how your color perception adapts and that you really can't trust your eyes to judge color objectively. To "see the difference" objectively you need a baseline your brain trusts. For lack of any better option setting Custom WB off a known neutral target is your best available benchmark.
When you need to be concerned about color management is if you set custom WB off a gray card record a full tonal range image (detail in shadows and highlights) and the image doesn't look neutral on screen and print. If it doesn't look neutral on the screen or the same detail the eye dropper values indicate it should have there's a monitor calibration problem. If you get exposure and color optimal at capture even if your monitor is way out of calibration if you don't change anything and just print it, the print should look OK if the printer profile is accurate. If the print doesn't it's an indication the profile isn't accurate and you either have a mechanical problem with the printer or an out of spec batch of ink or paper that doesn't match the generic profile provided with the printer.
What I'm suggesting here it that for lack of a better one the best indicator of whether you have a color management problem that needs addressing is a picture of the wife out in the yard holding a Macbeth target taken after you set Custom WB on the camera off a gray card. If she still looks like the woman you married an the gray patches on the MacBeth target look neutral on screen and print you don't have a color management problem. If you hold the actual MacBeth target next to screen and print you'll see the match isn't exact perhaps but not off so much you noticed in the shot of the wife.
You should calibrate your monitor with your device of choice then check the results against the photo of the wife after you calibrate. That shot set with custom WB, not what you see on the monitor, becomes the "gold standard" baseline you trust as the "right" color because all other photos you take with Custom WB will look similar out of camera. If you calibrate the the monitor and the photo of the wife holding the target doesn't look right the problem isn't the file, something messed up the calibration. You can use the camera WB baseline to check the monitor calibration rather than assuming it is always perfect.
If you get a new paper or batch of ink the first file you should print should be the one of the wife. Does it look identical to all the other test print of the same baseline reference file? If not then you might need to get a custom profile made for that paper. Should you make it yourself? Did you make pants you are wearing? Leave the task of creating the profile to those who have the equipment and expertise to do it accurately.
Edited on Jan 13, 2013 at 02:29 AM · View previous versions
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