Printing optically on Kodak Supra Endura Digital paper.

Typical halogen enlarging bulbs have a brief phase of startup color temp which differs from both the stabilized color and the final second or so of fadeoff. Short bursts can be unpredictable, even in a cumulative sense. It's a different ballgame than pulsed xenon or laser exposure.

Putting aside reciprocity failure, I had thought that an additive head with narrow band RGB filters would be better than a subtractive head, as it would more closely mimic the RGB characteristics of a digital laser printer. I understand Drew's point re: shifts on startup and fadeout, and due to heat during exposure, but I am willing to bet these are minimal and somewhat consistent. This seems to leave the main theoretical problem as being potential crossovers due to much longer than designed-for exposure times. I am about a week away from having the time to test this, but it should be interesting.

Putting aside reciprocity failure, I had thought that an additive head with narrow band RGB filters would be better than a subtractive head, as it would more closely mimic the RGB characteristics of a digital laser printer. I understand Drew's point re: shifts on startup and fadeout, and due to heat during exposure, but I am willing to bet these are minimal and somewhat consistent. This seems to leave the main theoretical problem as being potential crossovers due to much longer than designed-for exposure times. I am about a week away from having the time to test this, but it should be interesting.

I found this thread here:
https://www.photrio.com/forum/threa...mise-of-kodak-supra-endura.53931/#post-787586

If you read through it, you get the impression that optical printing works, but with a bit of crossover especially if fleshtones are optimised. Also, as predecessor papers had no reciprocity failure for exposures up to ten minutes, it is unlikely that their "improvement" would also. We shall see.

I have not used this paper but a few years ago I bought a Kodak paper called Royal Digital (it was the middle of the line) and it worked fine. I used the RA-4 RT chemistry at room temp for 2 minutes with good results.

I know someone who built a big rheostatic version of an additive colorhead using about 30 bulbs. It was a chore to use. It's like chasing your tail once the narrow-band filters overheat. My own additive colorheads run cool, using "sandwich" or "trimmer" dichroic filtration. But the feedback circuitry is ca mid-90's and temperamental. There is an option, but it's expensive and involves the even bigger headache of sine-wave control which can only be done as long as the necessary specific software is available, which generally ain't long! Durst intended to convert their 8X10 colorheads to additive, but then abruptly closed their entire commercial division. The components ended up in six additive aerial film enlargers at the NSA. But those run quite hot and need the filters replaced every six months - expensive! Designing a good additive colorhead is much more difficult than a conventional subtractive unit. Beseler sold a couple of additive models once, but soon flaked on warranty coverage.

I havent used "Digital" kodak paper but I used Fuji DPII wich is intended for digital exposure. It works fine with my halogen lamp and filters. Exposure time is somewhat shorter if compared to norma crystal archive. The paper has a higer contrast and saturation. I would give it a try if you like that paper

First of all, he's contemplating making 30X40 inch prints, which is a significantly greater magnification than 8X10 etc. And we don't even know what film format is involved. So until he tries his own test strips, it's hard to say if he has the gear to make it work or not. I ordinarily print 30X40's from 8X10 film, which is only a 4X linear magnification. But if this was done from small format film, the magnification difference would involve either multiple f-stops of difference or unrealistically long times. Whole new ballgame. We don't even know the kind of enlarging lens hypothetically involved.