Look at the back print of some papers, such as FUJIFILM’s Crystal Archive Supreme HD, and the word ‘digital’ features prominently. Indeed, I’ve been told that current Fuji RA4 color papers are exclusively intended for digital exposure. But does that mean we can’t use them anymore for optical enlargements?
To an extent, the question is a bit of an academic one. I’ve been printing on FUJIFILM RA4 papers for a few years, and have printed on Kodak Royal ‘digital’ paper as well for a while. Stacked in boxes, I’ve got more than enough proof to show that it works – you can make color prints on these digital papers, with normal dichroic filter enlargers as well as LED contraptions. One caveat on the latter is that some care is needed in selecting proper LED wavelengths, but that’s an issue I’ve discussed at some length already.
But in principle, light is light, right? And isn’t that true, regardless of how we create and manipulate this light? Does it matter whether we:
(1) take a white light source and use dichroic filters to selectively cut certain bandwidths, then shine the light through a negative,
(2) take red, green and blue LEDs (of appropriate wavelengths) and vary their intensities, and also shine this light through a negative,
(3) use red, green and blue semiconductor lasers (again, of appropriate wavelengths), modulate these lasers digitally and scan them across the paper to expose an image without any negative involved?
You guessed it: it does matter. And the reason has nothing to do with these light sources per se. In principle, they’re all usable. The only real difference is that with the 3rd approach, we can perform all sorts of corrections and adjustments that we can’t do, or only with much difficulty using a color negative. And it so happens that today’s papers require such adjustments.
So, how come? Previously, when FUJIFILM made a color paper, each color layer was in fact made from two light-sensitive emulsions. Hence, there used to be six light-sensitive emulsions used in an RA4 paper: three sets of two emulsions. Together, these sets were tailored in such a way to create nearly perfectly tracking Cyan, Magenta and Yellow dye images. By this tracking, I mean that the response curves of the color layers are nicely parallel, which prevents color crossover.
Two things happened, however. Firstly, digital exposure systems like Durst Lambda and Océ Lightjet came along. These expose RA4 papers with digitally modulated lasers. Given this digital control, an inherent match between the response of the RA4 paper and a color negative is no longer necessary – there is no negative anymore, after all. Moreover, even if the color response curves of the paper don’t track very well anymore, this can be corrected in the digital exposure, and such corrections can quite simply be embedded into an ICC profile so they’re always applied automatically to every print being made. Simply put: color RA4 paper just doesn’t have to be quite as good anymore in terms of crossover performance than it used to. Other parameters such as hue purity and chroma are still very essential, as is batch-to-batch consistency, aging properties etc. But crossover is just less of a concern because it can be ‘corrected away’ digitally.
The second thing that happened has always been happening, and that’s a continuous pressure to reduce costs. RA4 paper is a volume market and a commodity, and all sorts of market pressures, including competition between Kodak and FUJIFILM (but not limited to this) constantly press engineers to conceive of ways to get similar performance at lower costs. Given the digital story above, one possibility a number of years ago was to reduce the number of color emulsions in each color layer from two to one. The technical cost of this intervention was that color layer tracking was no longer quite as perfect – in fact, it has become quite compromised by the old standards before the advent of digital. The economic cost, however, was worthwhile. And the technical drawback actually wasn’t much of a drawback at all, because the flexibility of digital exposure could still achieve the same overall performance of the exposure-paper system.
The net result is that if you look at the color response curves of these papers today, they look more like this:
The main difference is that the steepness (gamma) of the green/magenta layer curve is no longer in line with the other layers. I think the toe and shoulder behavior are also different, but I’m not entirely sure on this. As said before, for digital exposure systems, this is not a problem. The ‘new’ papers have been in use for years already, ICC profiles are available from FUJIFILM and it’s evidently possible to make fantastic prints on these papers – at least when used as intended by the manufacturer.
For optical printers, like myself, this means that these papers will exhibit a magenta/green crossover. Since it is an actual crossover, there’s no adjustment of light source wavelengths, filtration settings etc. that will make the problem go away. The only way to work around this is to create a color correction mask that brings the curves back in line with each other. Personally, I’m not quite prepared to go that far. Color masking, especially to get it right, requires extensive calibration using panchromatic film, and for me, that’s a cost-prohibitive and overall unattractive (i.e. excessively boring/tedious) endeavor.
So does this mean that this is the end of the road for optical color RA4 enlargement? Well, yes, and no. Yes, in the sense that the current generation of FUJIFILM papers simply is no longer suitable for optical enlargements with high requirements on excellent color accuracy. It’s still fine for this in its intended use, i.e. in digital exposure systems – evidently. It’s also conceivable to make these papers work magnificently with supplementary color masking, if one is willing to face the effort and costs involved of doing so.
And there’s the slight possibility that not all papers in the market have undergone this change. For instance, Kodak Alaris still explicitly mentions optical enlargement as a possibility for their papers. At least, in the datasheet that Google retrieved, which dates back to 2017. This still leaves a number of unanswered questions: is this information still accurate? Now that Endura paper manufacturing is in the hands of Sinopromise and Kodak has no direct involvement in it anymore, are they still maintaining this optical printing compatibility? And this compatibility, how good has it been over the past years anyway? The fact that you can expose a paper under an enlarger doesn’t mean its color rendition will be dead-accurate – and the Kodak datasheet isn’t specific on the actual performance.
Another, and more relevant source of light at the end of the tunnel, is that for all intents and purposes, it’s evidently still possible to make very nice prints even on FUJIFILM ‘digital’ papers using an optical enlarger. I’ve burned several rolls of their ‘new’ papers, and the prints are really nice. Are they perfect? Well, evidently not – it’s impossible that they would be! But they’re very nice as they are, satisfying to make, and they look perfectly natural. The crossover that inevitably is there, is not necessarily disastrous. And for me, that’s more than enough reason to keep printing RA4 color in the darkroom from time to time.