Besides cross-processing, colour transparency film has another way of creating an image that is different. You may be familiar with B&W infra-red film. This gives an "other-worldly" effect by recording the infra-red light reflected by the subject and, depending on the filter used, some of the visible light as well. There has been a colour reversal infra-red film around for some time. Used mainly by the scientific and medical world, it needed the old Kodak E4 process, run only in a few specialist labs and as a kit, and was very expensive. It was incompatible with the E6 process, not least because it can strip the emulsion off E4 film. Kodak has now brought out an Ektachrome infra-red film that can be E6 processed. Since we humans can't see infra-red, the processed image changes infra-red to red, red to green and green to blue. A yellow filter needs to be used over the camera lens to stop blue light getting through and fogging all three layers, so blue appears as black. Different filtration could give some interesting results, just so long as not too much blue gets through. I've not tried cross-processing this new film and it may not work.
Want to see the slides you shot straight away? Polaroid make several "instant" 35mm slide films, covering B&W, colour and blue and white (yes, blue, for title slides and some special applications). They need a special little Polaroid processor and are not cheap. The colour films are interesting because they do not develop a dye image. Instead they use a much older method of a very fine screen of red, green and blue filters over a black and white film.
I mentioned last time that Kodak Direct Duplicating film doesn't work in the same way as normal. It's used for making B&W copy negatives without the need for an intermediate positive or reversal processing. It makes use of the Herschel effect discovered by Sir John Herschel. He found that a latent image in a silver halide could be destroyed by exposure to red light or infra-red radiation. Later it was found by others that the effect could be dye sensitized so that an overall fog could be destroyed by light, an effect known as sensitized Herschel Reversal.
With thanks to Guy Selby-Lowndes for the information in the last paragraph.
© Barry Leighton FRPS