Soft proofing

Yesterday, I attended Charles Cramer’s excellent lecture at the Sunset Center. Charlie asked me to say a few words about soft proofing. Some things occurred to me that I would have said had I more time and presence of mind. Fortunately, I have this blog.

Soft proofing is visualizing the final hard copy from an image on a monitor. The concept goes back to the eighties when computer systems became popular in publishing. In those days getting a hard copy proof was by no means as simple as hitting control-P and waiting for the printer to do its thing. To get an proof from an offset press involved having highly-paid craftsmen fire up to a large machine and run many copies (since the first ones wouldn’t exhibit representative colors). There were some ways to simulate in hard copy what the press would eventually produce (eg 3M’s Matchprint). These were less cumbersome than actually running an offset press, but were still time consuming and expensive.

Because getting to a hard copy proof was so difficult and expensive, there was a great deal of interest in being able to proof on the monitor. This turned out to be fraught with difficulties, many of which persist to this day.

The first difficulty is for the most part solved today. That’s getting the monitor and printer calibrated so you can produce the same colors on each as desired.

The next obstacle was actually handled better in a prepress environment than it is by most current photographers: getting the viewer (that’s you) adaptation standardized, both for the print and the monitor. Businesses painted entire rooms neutral gray, bought D 50 fluorescent light bulbs, sealed off all the windows, and constructed special viewing booths for looking at hard copy output. Most photographers don’t go to all that trouble, and I sympathize. It is important, however, to make your monitor viewing adaptation consistent, which usually means restricting the amount of daylight that enters the room.

The next step is getting the brightness the same for the monitor and the hard copy. In the old days it was hard to get the monitors bright enough to match the lighting levels normally used for hard copy evaluation. These days, with bright liquid crystal displays, the situation is typically reversed, with the monitor being so bright that the actual prints tend to be too dark.

Once the brightness is standardized for both the monitor and the hard copy, the next step is getting the white point the same. Since the standard viewing conditions in the prepress industry call for D50 lighting, the old method was to adjust the monitors for that white point, even if it made the low monitor light level even lower. These days, it seems most photographers choose D65 for the white point, in spite of today’s brighter monitors. I suspect that the yellower appearance of a monitor with a D50 white point puts off people who aren’t used to it. I’m one of those people; knowing that my work will hardly ever be viewed in D50 light (actually, it will probably most often be viewed in light that is even yellower than D50), I set my monitor to D65 and count on the white point adaptation mechanisms of the human eye to smooth over the differences.

The next thing to consider is the surround. Almost all photographs are displayed with a white surround, and it makes sense to use a white surround on your monitor as well. In order for this to be effective the surround has to dominate the visual field. This means displaying the image that you are judging so that it is much smaller than it is when you’re editing it. I think having the maximum image dimensions about a third of the overall monitor dimensions is about right, but that’s not possible to achieve in Lightroom if the files are big.

Next up are gamut mismatches between the monitor and the hard copy. The usual monitor can display a far greater range of colors than just about any printer can print. This means that it’s easy for a photographer to produce colors during the editing process that the printer can’t print.  You can deal with this problem by using the soft proofing feature of your image editing program, which will show you how the colors in your image file will be mapped for your particular printer and paper. However, one gamut mismatch problem remains: what it your monitor can’t display all the colors that the printer can print? The monitor is good at displaying bright, highly chromatic colors. Printers are good at handling dark chromatic tones. There may be some dark blues and greens in your print that you can’t see on your monitor. There is nothing that can be done about this at the soft proofing stage except to keep it in mind.

The last difficulty involves the way the brain perceives color. If it decides that something is self-luminous, rather than just reflecting the light that falls upon it, then it tends to respond to the colors differently. This is not a very strong effect, but it was of sufficient concern that about 20 years ago, researchers went to a lot of trouble to hide the fact that the monitor was producing the proof image by covering the edges with a mask, controlling the lighting of the mask, and keeping the viewer from getting too close. All of these shenanigans yielded more accurate soft proofing.

In brief: soft proofing isn’t accurate enough for artists to dispense with actual hard proofs. Calibrate your monitor; standardize your adaptation; get the brightness and the white point right; use a white surround in your image editor; watch those dark greens and blues. That will get you close. For the final tweaks, you’ll need to make a real proof.