My lab (unfortunately long closed) used to make all it's internegs by enlargement on to sheet film, however they had the best copying set up available, essentially a De Vere 5x4 head used as a light source with a copy camera above it. You do see these for sale sometimes.
I have to disagree with Bob here as this gave the highest possible quality internegs, it was also used to make 5x4 transparencies from 35mm Kodachromes etc.
I missed the part about the OP wanting to do contact prints, I am just addressing making negs from slides for enlargement.
Well Ian my labs did both ways , the easier way is to enlarge to a 4x5 sheet, the harder way is to contact, but IMHO and those of our clients were the contact internegs were vastly superior. one less optical projection if you want to think about that.
Making contact internegs is a pain for dust control and we had lots of little tricks for that. Worth the effort.
Now I still hope you send me those fix formulas , and when I get over there I am still welcome for a spot of tea eh.
Originally Posted by Ian Grant
I don't think you will have any trouble using Ortho film...just filter to get the greens where you want them. While I like the contact interneg process, I'd try the enlargement process first to see if it works good enough for you. My only problem with Ilford's sheet film in ortho is where do you get it?
For pos/neg or neg/pos, I would always contact print and then make the final neg or pos by projection.
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Using ortho film, the red colors will come out very dark. I did this sort of thing back in the 1960's using Kodak's Gravure Copy Film (an ortho slow-speed emulsion). It works fine by projection. Contact printing will work, too. I did it for an enlarged negative for B&W photo christmas cards.
I might have used Dektol developer. For a negative that will be contract printed, developer isn't so critical as getting your exposure and contrast right. If you plan to enlarge, then developer will matter more (because grain structure will matter more).
Slow speed film is useful for this sort of thing, so if you go for panchromatic film, Efke 25 might be advisable because of its slow speed.
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First of all you turn your easel 90 degrees so it can accept 4x5 film instead of 5x4 (which I've never
seen - perhaps it has something to do with which side of the Greenwich Meridian you're on) - but
seriously ... To do high-quality work you need an actual vacuum filmholder on the baseboard and a
lens suitable for duplicating. I use Apo-Nikkors rather than general enlarging lenses for this purpose.
Everything must be exceptionally precise, and your light source should be quite even. Choice of film
can be any number of things, but if you choose ortho it not a lot different than shooting ortho outside, except that it will be slower under a tungsten light source and be slightly skewed unless you
balance your colorhead to a cooler Kelvin temp resembling daylight. Takes a little practice, but in principle this is pretty simple conceptually.
Lots more advice! Many thanks. Premortho - Ilford Ortho is available in the UK from Silverprint.