Don Rommes (LensWork #100) writes to ask about computer monitor luminosity and how it might affect how we print the digital files we received in submissions to LensWork.
I have no doubt that you match the image on your computer screen to the printed page, but what if the photographer calibrates her monitor to, say, 140 luminosity, and yours is different? Then you might be seeing a darker image than she would and you would print it to match.
I never really thought about this much before, but I wonder if this occasionally creates an inadvertent mismatch between what the photographer intended and what LensWork is showing? Perhaps, for those who do not submit prints to match, you could give a guideline for submission that addresses this (theoretical) issue of luminosity calibration for those who are interested. Just a thought.
Don asks a great question that will require a somewhat detailed explanation. All this brings us to the question, Why? Especially, why would one photographer's system be different than another's if both are using hardware calibration? Could be a profile mismatch. Could be hardware luminosity differences. I'm sure there are lots of other variables, too. This is precisely why we ask for match prints. When I prepare digital files for print, I use the three match prints we always request to accompany a digital submission as the ultimate judge of densities rather than the digital files. Visual tonal adjustments are always subject to so many uncontrollable variables and even personal opinions that we find it a much better strategy to measure densities with a calibrated densitometer.
Typically — and this was specifically the case with Don's images, too, so nothing out of the ordinary — I'll work with the digital image files and the match prints to establish a tonal curve that brings the digital images into calibration on our system. I do this by measuring the densities on the print in smooth-tone areas and comparing that to the same smooth-tone area in the digital file. (My densitometer gives me % readouts that can be perfectly translated to the % numbers in Photoshop or Lightroom.) I tweak an adjustment tone curve in the digital file until the print density percentages match the digital file percentages up and down the tonal range. I repeat with the second image and often find the curve is slightly different than the first image's curve. Repeat with the third image, again tweaking the curve. Then I take this final curve and apply it back to the first image as a double check to see if it looks visually even more accurate. By working with three images, I have this sort of "statistical average curve." I then simply apply it as an adjustment layer to all the images using a blatant assumption that any differences between the photographer's computer and mine will be consistent across all the prints. This takes care of any discrepancies between the photographer's digital files and whatever monitor/profile they might use and my versions of the digital files calibrated for our system and the press.
These tonally adjusted and calibrated digital files are then used when I apply our duotone curves as a final step. In theory, everything is then calibrated and perfectly ready for the press. There is, however, one final variable — the plate curve. The printer keeps their machinery calibrated by using a plate curve to adjust the dot densities on the printing plate for each printing head on each press. It's a constantly moving target for each press and as the plate materials change. The integrity of the printer is often measured by how tightly they try to control this consistency. Plate materials being what they are, however, even batch-to-batch variations can creep in. This is precisely why I measure final printed densities on test step wedges for both grayscale and duotones as a final check. These control step wedges are critically important because they allow us to know with certainty that we are achieving on the printed page the tones that are inherent in the calibrated digital files.
The real world being sometime recalcitrant, it's not unusual for me to request a new plate with a plate curve adjustment when I find the final densities are off by 7-8% or more. The densitometers have an accuracy tolerance of +/- 2%. If we are within 3-4% of actual numbers, we feel this is a real victory. The hardest tones to hold are the deep shadows — 95% tones mapping to 95% make me dance with glee. This is the key to preserving shadow detail. The 1% dots are problematic if they disappear, so we are more willing to accept a tone variance that's a tad dark at that end of the scale. Complicating matters, measuring right off the press the inks are still a tad wet and there is a "dry down" factor just like there is in the darkroom. Below is a scan of my control step wedge from the press run for issue #100 so you can see — coffee stains and all! — what I'm talking about.
As you can see, if anything we were a few points darker in the middle of the scale than perfect calibration on this run — typically not enough that anyone would see, however.
As I often find, the images on the monitor appear to have more contrast, but that's because the monitor itself has more contrast than the printed page. This really manifests itself in the darker Zone III type tones which always appear darker on the monitor and in the light Zone VIII and Zone IX tones that always appear brighter on the monitor.
By the way, this is essentially the same workflow I use in my inkjet prints and my Epson printer. So why not "soft-proof?" I've always found the concept of soft-proofing to be a great theory that simply doesn't work. Trying to make a monitor look like a printed page is akin to trying to make an orange sound like a clarinet. Measured densities are the best strategy — from Photoshop/Lightroom all the way through to the printed page. To quote that great philosopher Yogi Berra, "In theory there is no difference between theory and practice. In practice there is."