Making positive transparencies from negatives?

[benrains]

I imagine this is pretty easy question to answer, but what are the best ways to make b&w positive transparencies from existing film negatives? I'm not looking to create enlarged positives, although I suppose the process would be similar, but rather 1:1 copies. The idea of contact printing to regular sheet film had initially crossed my mind, but I thought I'd check to see if there's something else more suitable.

[Greg Lockrey]

First, the negative image is developed but the undeveloped silver halide salts are not removed by fixing. The negative image is removed by bleaching with a solution of potassium permanganate and sulfuric acid, which is removed by washing and a clearing bath containing sodium metabisulfite or potassium metabisulfite. The remaining silver halide salts are re-exposed to light, developed and fixed, and the film washed and dried. I may have more in the morning but I have to dig out my old notes from 20 years ago.

[benrains]

Greg, that sounds like a way to make positives from an original shot. (Which is still good to know. :-)

In my case I already have processed negatives that, in addition to making regular contact prints on paper, I'd also like to contact print onto film (to make a positive transparency). I'm just curious to know what sorts of film are well suited to being printed onto. Preferably it'd be one with a very clear film base, and ideally it'd have low enough sensitivity to light to allow time for darkroom manipulations like dodging and burning.

[Robert Hughes]

Try some slow speed ortho film for contact printing.

[benrains]

Try some slow speed ortho film for contact printing.

Thanks. Checking the ortho lithography film offerings on Freestyle and their accompanying descriptions, this sounds exactly like what I need.

[JRFrench]

Im not sure you want litho film, isn't that really high contrast? Something like the Rollei Ortho 25 from freestyle or something should be good. You can use a normal film like FP4 but you have to handle it in total darkness and the exposure will be fairly short. Safelight handling of ortho film will be very welcome, and its cheap.

As for processing a negative into a positive, Greg was on the money: http://www.darkroom.ru/info/manuals/ilford_reversal_processing_manual_eng.pdf

[domaz]

There is a bunch of resources on APUG about how to develop regular film as B&W slides. Just contact print them on regular film and go through one of those processes and you are good to go. They are not easy processes though- require mixing your own bleach etc..

[Robert Hughes]

The previous 2 posts are assuming the OP wants to make reversal slides, but in post #3 he says he has previously processed negatives and wants to make positive transparencies from them - essentially a negative of a negative.

Another way to handle this could be to scan the negatives, reverse to positive in Photoshop and print to transparencies. That would save a buncha film.

[Mark Barendt]

I think I read somewhere that one of TMax 100's design criteria was for this type of duping, Delta 100 would probably work too.

You biggest challenge will be defining the right exposure.

[Jim Michael]

Lith film is nice because of the clear transparent base (no blue or other tint like you often see in TX etc.) and it's nice and slow. It's high contrast if you use a high contrast developer (something with a lot of hydroquinone IIRC) but if you use a developer like HC110 etc. should be pretty normal tonal range like your original.

[benrains]

Quoting from Freestyle's description of their Arista-II Ortho Litho film:


It is an excellent quality graphic arts film that is a replacement for Kodak Kodalith Type III Ortho Litho Film. When developed in standard A/B Lith film developer, this film will yield high contrast (black & white only).

Develop in diluted form of standard B&W paper developer to obtain continuous tone results for use in creating enlarged negatives for contact printing.

Arista-II Ortho Litho Film is also used by many photographers for use in creating highlight masks for fine art printing and for creating enlarged negatives, in a two-step process, for contact printing and alternative processes.

Continuous-tone results can be achieved by using a dilute working solution of standard paper developer. Dektol 1:7 or 1:9 is a popular dilution to achieve continuous tone results. Ethol LPD, Agfa Neutol, Clayton Extend Plus, Clayton P-20, Nacco Printol, or any of our Arista and Arista Premium Paper Developers are also recommended. Your individual optimal dilution and developing time will vary based on your desired results.

I actually know some people who shoot this as a cheap continuous tone LF film and process it in diluted Dektol. In that application it has the disadvantage of being slow and not being a particularly good continuous tone film, but I don't expect that will be a problem for creating a good positive from being contact printed. Its reduced sensitivity to light should allow me to make test strips like I would with b&w paper to find the right exposure.

At some point I may play around with developing my original shots as reversal film, just for the sake of experimenting, but in most instances I'd rather have the negative be the "master" so I can still easily print it on photographic paper.

[Mick Fagan]

I used to make about 10 or so B&W negatives from colour transparency film each week. The film of choice was TMax 100, we developed it normally and we then could make B&W prints from the negative.

The negative was reversed, but we just enlarged through the back door. I would suggest you use 4x5" film as it is quite stiff, quite cheap, quite good. Other larger formats are usually more expensive if you are thinking of projecting onto B&W film, then it just isn't as sharp as a contact print emulsion to emulsion.

We also used to make B&W transparencies doing exactly the same thing, but starting with a B&W negative, contact printing under an enlarger onto a darkened easel (black paper).

Develop normally and take it from there.

Basically we used a heavy sheet of glass and the 4x5” film was registered by using the easel and some tape for positioning.

The real problem is dust, we used compressed air religiously for everything, then switch off the lights, whack the film down emulsion to emulsion, glass on top, hit the button, pull out and develop. Sometimes I also used air in total darkness when placing the unexposed film down, a bit hit and miss, but generally worked well.

An enlarger is a good source as you can time the exposure accurately, removes another variable.

We actually used roller transport for film developing so we had the film developed and dry inside about 15 minutes. Neg onto the light box, make an exposure discussion/decision/guesstimation and do another neg.

This was over 20 years ago so the TMax film of today will be different, but it was about the best around for this stuff at the time.

Mick.

[Vlad Soare]

I did that several years ago with dental x-ray film, developed in paper developer. It was sensitive to blue light only, so it worked fine with my safelight (light orange).

[Mark Sampson]

The traditional film for making b/w trransparencies from b/w negatives is Kodak Fine Grain Release Positive (7302) film. Basically a paper emulsion on film, it's designed for making release prints of movies, and is/was made in sheets as well as 35mm (5302). IIRC it's blue-sensitive and develops in Dektol 1:2. It's been a long time since I used it, though, and I can't say if Kodak still offers it.