Digital creation of analogue negatives for alt-process

As some of you may know, I've built and been using a digital UV light projector for making alt-process prints with good results for a fair few months now. However there are limitations to the process.

The main issue is that the LCD blocks a huge amount of light, about 96-97% of the UV light never makes it past the LCD screen even when it's set to maximum transmission. In the best case this just means long exposure times, but for some processes the results are non-linear with exposure, and below a certain light energy there's no effect at all. For example when carbon printing using DAS with the current system my shadow densities are pretty poor because past a certain depth there's just not enough UV energy to harden the gelatin any more, and there's really nothing I can do about that.

Another issue I've encountered is image persistence or burn-in like CRT computer TVs used to get. In theory this should be reversible, but I'm really having trouble getting rid of a ghost image from a previous test pattern and it's ruined a print I just tried to make. I think I might be able to prevent this in the future, but for now I'll probably have to replace the LCD screen which isn't cheap.

These two problems have me thinking of alternatives. I still want to be able to edit and print from digital files because that's my workflow, and I still want to use my projector as I don't want to deal with having an inkjet printer for making digital negatives (I've got one and it's always been a pain). My projector is basically a UV enlarger, with an LCD screen where the negative would be, which makes me think that I could replace the LCD screen with a film negative and get a significant performance improvement. This is because a film negative would block far less light than the LCD screen, I'd probably get an order of magnitude increase in light, which means much faster exposure times and much greater energy for processes like DAS carbon. It's also more robust as there's no chance of LCD screen burn-in and I can always make a new negative if one gets damaged.

So the question is, how to get a film negative while using a hybrid process? My thought is that I can put the same type of monochrome LCD screen I'm currently using in the projector in front of an LED panel and literally take a photo of it with my 4x5 camera and some B&W film. I could then develop the film and put it into the enlarger for printing. It's more steps in the process and more work, but maybe not that much harder and would significantly improve my exposure times (and eliminate the chance of burning another LCD screen). The film should easily be able to resolve the detail in the LCD screen (which is the equivalent of about 32 megapixels) and the resolution of the screen is already fine for pretty large prints, so the film copy of the screen should also be fine (actually the grain the film adds would probably be an improvement).

For those of you who do alt-process prints fully analogue, what are your suggestions for film stock, developer, and exposure/develop settings to get a good density range for alt-process? With the LCD screen I can use calibration curves to change the contrast of the scene that gets exposed onto the film, so I'd be more interested in getting a high enough density range for carbon as a baseline which I can dial back for other processes if needed. I currently use FP4+ as my 4x5 film of choice and I have rodinal and LC29 but happy to give anything a shot.

AndrewBurns said:

For those of you who do alt-process prints fully analogue, what are your suggestions for film stock, developer, and exposure/develop settings to get a good density range for alt-process?

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As you know, this is about the only part of your question that I can answer, since my own thinking is also pretty much stuck at the same point as yours. https://tinker.koraks.nl/photograph...e-of-digital-output-for-alternative-printing/

My preferred sheet film at the moment is Fomapan 200 (usually exposed at ca. 100) developed in a non-staining developer, I presently use ID62 in a replenished system and I don't control development time etc. very strictly. Dilution from the concentrate is around 1+2 (but that's also uncontrolled) and I develop for 5 minutes or so, sometimes 6, at room temperature in a tray with an agitation cycle every 30 seconds. When the negatives are dry, I have a look at them, maybe measure some densities, and usually then proceed to intensify them using chromium intensifier (permanganate can also be used) if they are for DAS carbon or salt printing. For the redeveloper I either use ID62 or sometimes a staining developer like pyrocat, but that gives a massive UV density boost and can produce challenging highlights esp. for DAS carbon because the stain also floods the space between the grains.

FP4+ is also an excellent choice. Really, you could use pretty much any film, but higher-speed films like HP5+ and Fomapan 400 can be challenging or may not work well at all due to a sloping gradient and high b+f.

You should be able to make an exposure with your LCD enlarger onto 4x5 or 8x10 film to make the digital-to-analog step. I wouldn't not bother with the camera in this setup. Just 'print' on the film as you'd do on paper. Use visible light; wavelength doesn't matter much. You can calibrate/linearize as you see fit.