Can be done but would need specialist equipment to do it
Do a google search for "slides from digital files" to see a list of people who offer the service, seems a bit pricey bu could be worth it is you were going to use them a lot.
I think, Postdog, you will find transparencies (slides) are created from positive film, there is no negative like you had/have with photographic prints. The slide film is developed as a positive image.
Yes is is possible to print a computer image onto film, otherwise Computer Generated films like Toy Story would never have reached the cinema.
Thanks to all. I think I shall have to either go down a different route to present the images, as postdog says, or I might just try putting them one my monitor screen and photographing them with a 35mm SLR camera loaded with slide film; a bit crude, but I don't want to spend a fortune on this project.
I bought a. Epson V200 scanner with a slide adapter and I've copied all my slides onto the computer. It was easy to set up and to use. It cost about �70 which was alot cheaper than commercial companies would have charged to transfer them for me. The enhancement software is very good, not only with transparencies but digital photos.
Sorry, just reread your question and realised I've talked twaddle.
You can get transparency acetate film to use in your printer however, I used to make acetates for the OHP when I was teaching this way.
Thanks cc1, but I have used your method of printing on acetate from photoshop; it's ok for large sheets which can then be used in an overhead projector, but when the image is reduced to 35mm the quality of a printed, rather than a photo image, is very poor - there just aint enough dpi. I guess I'm trying to do what you first suggested only in reverse, and I was hoping someone had come up with a magic solution.