What has to happen before large numbers of people view mechanically reproduced images in preference to seeing the actual images on the walls of museums? In this post, I’ll talk about technology, and next time I’ll work on the social/business/legal issues. I expect the technical part to be easier.
From a technical perspective, in order to get audiences preferring the copies, we need to make the experience of viewing mechanically-reproduced images unequivocally better than today’s museum experience of traditional photography. What needs to change to get that to happen? Before we talk about that, we need to pick a standard against which to measure the new processes. Of all the traditional photographic processes, silver prints have the greatest acuity and dynamic range. Now that Cibachrome and dye transfer have all but disappeared, of the current color chemical photographic processes, chromogenic prints have the highest quality. Second, we have to take into consideration the different viewing conditions; the reproductions, free from the burden of striving for permanence, can be illuminated much more brightly, which means that they’ll look better even if the quality is not quite the equal of the originals. So let’s rephrase our question: what has to happen before mechanically-reproduced images have nearly the same quality as today’s traditional silver and chromogenic prints?
For the first part of this discussion, I’ll assume that the source document is an image on paper, and that what is desired is as close a replica of that image as possible, either in a book, in a poster, or hanging on the wall of a museum. At the end of the post, I’ll consider a different tack that can yield even better results.
Better offset printing technology. I think Jensen covered this very well for black and white. Because of his focus on black and white reproduction, he didn’t mention that the black-and-white printing technology he described was invented for color printing, and the current improvements in printing technology apply equally as well to the color world. In addition, offset printing, like inkjet printing, is moving in the direction of using more than three color inks. I’m not talking about various dilutions of the same hues, as in light cyan, or my favorite printing oxymoron, light black. What I mean is the addition of colors like red, orange, and green to the standard set of cyan, magenta, and yellow, the objective being to increase the color gamut. At its best, offset printing can produce a far greater color gamut than that obtainable from a chromogenic print, and can reproduce any color in a C-print (which uses only three dye colors: cyan, magenta, and yellow – no black). To enjoy the benefits of the technology Jensen describes, we merely have to wait until today’s state-of-the-art printing technology becomes widespread and inexpensive.
Better low-volume printing technology. Posters and books can enjoy high enough volumes to make offset printing economically attractive, but using a standard offset press to get one or two prints is horrifically inefficient. There are offset presses manufactured for the print-on-demand market; they are economical for short runs, but don’t produce the ultimate quality. I think that the most likely candidate for photographic-quality prints is the familiar drop-on-demand inkjet printer. It’s already better than a color C print; we can get a Dmax of better than 2.3, a sufficient range of colors (way more than sufficient with the printers that use red, orange, green, or blue inks), and minimal bronzing. When compared to a silver print, we’re close, but not quite there; Dmax is better than we need, but resolution and smoothness won’t match a contact print, and bronzing is still a problem (the viewer is more sensitive to bronzing on a monochromatic print than a color one), although it’s gotten much better recently with the introduction of papers that emulate the surface of a non-ferrotyped glossy silver print. Bronzing is not as visible when prints are displayed under glass, which is the way museums normally handle photographs (but maybe they wouldn’t need the glass with copy prints that they consider sacrificial, providing a more-intimate viewing experience), and I expect bronzing will be sufficiently well-controlled soon. If it’s not, coatings can be used to hide it. Illuminant metamerism (change in color of an object when lit by light of different spectra) is much less of a problem now that printer drivers are creating most of the tonal range with the grey and black inks, rather than counting on cyan, magenta and yellow together adding up to a neutral black.
Color-managed capture. Usually, museums already have photographs of most of the works in their collection. That doesn’t mean that they could make credible copies from those photographs. There are three technical problems with the reproductions that museums typically make. First, they are usually film transparencies, which by their nature cannot store the entire gamut of colors of a photographic print (although they can store many colors that cannot be reproduced in a photographic print, and anyone who’s printed a ‘chrome knows). Second, because the museum’s purpose is to represent the object in databases and low-resolution catalogs, they don’t use sufficient resolution to capture all of the detail in the original photograph. Third, since the images weren’t captured in a color managed workflow, there’s no way to tell the colors of the original print from the capture. For all these reasons, museums interested in making high-accuracy copies of photographs in their collections will probably need to re-photograph all of their images.
Once a museum has signed up to re-photograph their collection, their color-management problems don’t instantly go away. Where reproduction of color is paramount, the standard filters of color scanners and cameras are inadequate; for color-accurate reproduction scanning needs to be done with special filters that can, with some math, replicate the response of the human eye. The illumination needs attention, too, but that is usually less of a problem.
Color management applies not only to color images, but also to toned black-and-white silver photographs, as well as alternative processes with distinctive color casts, such as palladium or cyanotype. Black-and-white images do allow a great deal of simplification; if we ignore split-toned (deliberately or not) prints, the color of the print can be described in three numbers that apply to a monochromatic image.
All in all, color-accurate capture can be a daunting challenge to any museum, and an almost-insurmountable one to a small institution with no expertise in the subject. Perhaps it is better to take small steps at first, and start with black and white images. Careful monochromatic captures and colorimetric or visual chromaticity matches should be adequate. Even black and white is not without its pitfalls. If the dynamic range of the copy medium is greater than that of the original, which will be the case for some contemporary and almost all older prints, should we use the increased range of tones, or should we faithfully reproduce the limitations of the original? If we do decide to use the entire range of the copy medium, what tone mapping algorithm should we use? There’s no easy answer to either of these questions.
Color-managed printing. Having a color-managed file doesn’t necessarily mean the right colors in the printed output. Industrial-strength versions of the same sorts of color management techniques that you use with an inkjet printer work just fine on an offset press. However, in spite of at least 15 years of effort by color-science-driven companies, these techniques are not the norm in the pressroom. Using specially calibrated proofing printers can go a long way to closing the gap. For inkjet printing, color-managed workflows are the rule rather than the exception, and today’s state of the art in color management is adequate for color images.
Standard color management techniques don’t work very well for producing duotones or tritones of nearly-monochromatic images. There are several reasons for this situation. The market for high-quality monochromatic images is substantially smaller than the color market. Human color vision is more sensitive near the neutral axis. There are a wide variety of inks used for duotones, so it’s harder to characterize these inks than the smaller set used for color reproduction. As with color, the situation is better for inkjet printing, although the present standard way of generating subtle shifts in image tone, using small amounts of highly-chromatic ink (the same ink used for full-range color reproduction), presents potential permanence problems.
In either offset lithography or inkjet printing of black and white images we can start with the colorimetric or visual chromaticity matches that we discussed for monochromatic capture.
What if we don’t start with a print?
Most of the photographic prints in museum collections were produced using traditional chemical processes, and embody subtle and difficult-to-reproduce adjustments – dodging, burning, bleaching, etc. — made by the photographer or a trusted assistant during the printing process. For those images, it makes sense to start with the photographic print. However, a growing number of museum images either started out as a digital file, or were scanned to that form on the way to becoming finished prints. The best way to get a high-quality copy of a digital image is not to print it, scan the print, edit the scan, and then print it again; it makes a lot more sense to start with the artist’s digital file and avoid the quality losses that inevitably occur with extra printing and scanning steps.
Since most artists don’t use color-managed workflows exclusively, they won’t be able to just ship off a disk and have that be the end of it. For artists, the final result is almost always the print, and even if they use color management to get the print close to what they want, they will almost always tweak the files to get the prints right, even if the tweaks make the images look worse on the monitor and throw off the colors embedded in the files. As an aside, I note that the UPDIG file interchange standards go a long way to achieving truly device-independent printing, and are a genuinely Good Thing. However, the present state of the art in color management—good but not perfect—and the way artists work means that digital files should be accompanied by proof prints that reflect the artists’ intentions. Or maybe artists should just go ahead and make the sacrificial prints themselves. Hit print once to make the “real” print; hit it again to make the one that’s going to see the bright lights. This has the wondrous effect of creating a copy that is precisely identical to the reference image.