why do photos need color correction prior to printing ?

Started Jan 24, 2013 | Questions thread
apaflo Veteran Member • Posts: 3,854
Re: why do photos need color correction prior to printing ?

coder01 wrote:

if the camera transfers the data it recorded straight and unaltered to my computer, and I make no changes to that data when i transfer it to the printer one would expect if the camera recorded the image properly that the print would look proper. isnt that intuitive ?

Yep it is.  Unfortunately what is intuitive is sometimes wrong simply because we are not logically considering all of the pertinent facts.

The missing facts in this case are because you are assuming the camera "recorded the image properly" which is virtually never true, and likewise the assumption that the same image sent to a monitor and a printer will necessarily look exactly the same which is also virtually never true.

What is true is that to get "correct" images you will have to adjust the camera for each an every exposure to match the amount of light, the amount of contrast, the color hue and the color saturation.  Or of course you can post process the image rather than use in camera setting, because that will allow much finer and more accurate adjustments.

Then, once you actually do have a "correct" image you will necessarily have to adjust either the monitor to match the printer or the printer to match the monitor.  It turns out that the most successful way is to "calibrate" the printer to a standard set of colors so that different papers and different inks all produce the same prints, and then in turn the monitor is adjusted to display the image to match the prints.

I'm skimming over the specifics of why that sequence works best, but rest assured it is far better than any other sequence.

one should not have to even look at the computer image, just send straight through, camera to printer, no changes requested/executed in any photo editing software.

Whatever notion it is that makes you believe you have a camera that produces "correct" images just because you pushed the shutter release button... it's a fantasy!  Really!

Cameras have a lot of wonderful automatic functions... and not one of them is perfect enough to always be right.  For that matter, once you start printing your own images the chances are very high that within a year or two you will become so critical of your own images that you'll come to think that not one single automatic function on your camera is safe to use without you personally adding your own little adjustment to get what you need!

the images are always too dark.

Compared to a monitor which always defaults to too bright.

But, another nasty little secret needs be told...  you can't judge the correct brightness of an image by looking at a monitor!  The only way to know is to look at the actual data, which is displayed by a histogram in any image editor.  The contrast must also be judged by analysis of data, not by viewing.  Viewing can be used to adjust color saturation and hue.  Viewing is also the way to adjust linearity of a gamma (contrast) curve.  Hence you set the range of contrast, or the maximum white and black levels using image data, and then adjust color and the tonal distribution while viewing the displayed image.  With a fully calibrated system that will result in a print that looks very very close, but not exactly, like what you see on the monitor before printing.  The reason they are close but not exact is because the monitor uses Red, Green and Blue lights to produce colors, and the printer uses ink that reflects Cyan, Magenta, and Yellow.  The monitor cannot produce highly saturated Cyan, Magenta or Yellow and the printer cannot produce highly saturated Red, Green and Blue.  So you get something very close, but perhaps never exactly the same.

there has to be a more comprehensive answer than blaming a monitor as the monitor did not change the photo.

The problem is that you didn't look to see if the photo needed to changed, and don't have a "correct" image to feed to the printer.  The printer simply can't make an image any brighter than the paper it is printed on, and the default calibration of a printer won't be far from correct.  The default calibration of a monitor is virtually always quite far, as others have already described, from what is correct for print previewing.

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