double-coated film

[Don Dudenbostel]

I work in x-rays as an art form and have used x-ray film for many years strictly for x-ray purposes. Mammography film is single coated on one side and general purpose blue or green sensitivity x-ray film is coated on both sides of the film base but not double coated on either side. To my knowledge there is no double coating on any x-ray film on a single side only. X-ray film is generally very grainy and if you enlarge you may get a secondary image from the double sided emulsion.

[gbogatko]

Fortran 400 is listed here. http://www.eightelmphoto.com/paper.htm

I don't know if they actualyl sell it, though.

Yes. It's the 400 speed -- one layer at 50 ISO and the other at 400 ISO.
Forte, unfortunately, is out of business (unless a miracle occurred while I was asleep).

GB

[Bruce Watson]

Are there any other sheet films made out there that are 'double-coated' in this manner?

I would be shocked to find as few as two layers on any currently made film. It's not 1921 anymore. I seem to recall a thread over on APUG talking about this a few years ago. Most modern B&W films have at least 5 image forming layers IIRC. The layers have various characteristics that add together to give the film its spectral response, its dynamic range, its graininess characteristics, etc.

Color films have many more layers (more than 20 for some films IIRC), some image forming and some not (filter layers, etc.). The various image forming layers are themselves composed of sub-layers for the same reasons that B&W films have so many layers.

For more I suggest searching around the APUG website, particularly the B&W forums. Lots of good information there, and at least one participant is a retired Kodak engineer. There's even an Harmon/Ilford rep who participates (but doesn't seem to be an engineer).