double-coated film

[gbogatko]

I quote from "Pictorial Landscape Photography" (The Photo Pictorialists of Buffalo, 1921)

"Our own preference is for Orthonon plates [...]. There are now several other brands of the same type of plate -- orthochromatic and double coated, the emulsion being very considerably faster on the surface than in the lower layer."

I know Forte made a double-coated film (think ASA 100) claiming the same characteristics (a slow and fast coating), but alas, Forte is dead, and I don't have much left.

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

George

[BetterSense]

Xray film is double-coated.It works fine; I keep track of which side was toward the lens and basically ignore the other side.

[Mark Woods]

Double, and even triple layers, of a given emulsion is common in color film. There is a Red, a Green, and Blue layer, and with higher speed films multiple layers are used. In B&W, I don't know.

[Drew Wiley]

I wasn't impressed with that Forte film at all. Got a much longer scale and far better
acutance with things like Efke 25, Bergger 200, and Fomapan (Arista)200.

[Robert Hughes]

Xray film is double-coated.It works fine; I keep track of which side was toward the lens and basically ignore the other side.
"Double Coated" - does that mean two different emulsions on the same side of the base, or the same emulsion on both sides of the base? :confused: Color film is similar to the former: X-ray film is the latter.

[Dan Fromm]

Xray film is double-coated.It works fine; I keep track of which side was toward the lens and basically ignore the other side.High speed X-ray film yes, and it has low resolution. I have some fish radiographs made with the stuff and they're not as easy to read as they should be. Small fish, though, and very fine details. There are single-coated X-ray films with higher resolution.

[gbogatko]

"Double Coated" - does that mean two different emulsions on the same side of the base?

I believe that's what they are referring to -- one fast and one slow. Fast gets the shadows, slow constrains the highs, all this with red insensitivity, being ortho film.

George

[gbogatko]

Xray film is double-coated.It works fine; I keep track of which side was toward the lens and basically ignore the other side.

Ah. Where does one get Xray film. I assume one must cut it down to 8x10 or 4x5 size?

George

[Robert Hughes]

Ah. Where does one get Xray film. I assume one must cut it down to 8x10 or 4x5 size?

George
You could try CXS Online (http://www.cxsonline.com/text/detailpage.tmpl?command=showpage&sn=31453&sku=CXS8582777&location=10011001) - I bought some a box of 100, 8x10 sheets for use at about 25 cents a sheet. The emulsion is very fragile, you have to be careful not to scratch it. Search through the threads here; there was a lot of discussion last fall about this film.

[BetterSense]

I don't think xray films have the characteristic you are looking for. They have the same emulsion on both sides of the 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 (http://www.apug.org/forums/forum13/) website, particularly the B&W forums (http://www.apug.org/forums/forum37/). 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).