On 11 March 2012 07:28, P. J. Alling <webstertwenty...@gmail.com> wrote: > > I'm sorry, by their ages past naming convention, Ektar should by rights be a > slide film. I didn't realize it was a reversal film. >
EktaXXXX wasn't a naming convention reserved just for transparency film such as Ektachrome. Other products used the "Ekta" prefix, among them Ektacolor, Ektapress, Ektaprint, Ektaflex, as well as the Ektar colour negative film already mentioned. BTW, I hate to play the Grammar Nazi, but slide films and reversal films aren't opposites, they are one and the same. You must have meant "negative" when you wrote "reversal". Simply explained, practically all emulsions are natively negative. Slide films have a reversal step during processing. Hence, slide film is called reversal film. There are (were) a very small number of natively positive products. Ilfochrome (formerly Cibachrome) is the one which most people will know. It is a dye destruction process, where the exposing light breaks down Azo dyes and renders them unable to be developed, leaving colour density only in unexposed areas. Dyeline paper (the newer alternative to blueprint paper) was a simpler type of the dye destruction where the dye in the white areas was destroyed by UV exposure while the remaining unexposed azo dyes were developed by ammonia vapour, to become the black lines of architectural drawings. Lastly there was a rarer process called autopositive or auto reversal. These materials had been exposed to the "point of reversal", a point of gross overexposure where any further exposure actually reduced the latent image density, i.e. more light = less density. This material was definitely a lab material, not a general photographic film. It had very poor tonal characteristic but was useful in graphic arts processes. regards, Anthony -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
