Are low-speed, sheet films harder to make than roll fims?

[mcfactor]

Are low-speed, sheet films harder to coat than roll films? I know that Pan-F cannot be made into a sheet film, is the same true of Rollei Pan 25?

I've recently made the move up to 4x5 from 6x7 and I feel like the amount of low-speed films decrease in inverse proportion to the film size. Right now there's pretty much efke films and rollei ortho. I would love to see Rollei pan 25 in sheets.

 

[Ian Grant]

There's never really been any demand for slow sheet film, the research into slow ultra fine grain films came about with the growth in use of miniature camera, which was how they used to describe 35mm film & cameras.

Commercial photographers who formed the vast bulk of sheet film users where perfectly happy with films like FP4, Plus-X and their forerunners.

It's really about the degree of enlargement required when shooting 35mm or Roll film compared to 5x4 and larger formats.

Ian

 

[mcfactor]

Its true that there has not been as much of a demand for slow sheet films. however, faster film is a newer invention, slow films have been around much longer. and until very recently there were many, many more options.

I guess what i was really asking was if an emulsion is already developed, is it that much harder to coat it on sheets, e.g., rollei pan 25. I know that the answer is 'yes' for Pan-F, so if it is 'yes' for Rollei Pan, is there something about slow-speed films that makes them harder to coat on sheets?

 

[tim_walls]

I suspect - though I'm open to correction - that it's not so much 'harder' as 'different'. Since any difference means expense getting the process right, there needs to be enough demand to justify the cost.

It would probably be cheaper for the manufacturers to just post a ND filter to all the people who want slower sheet film

 

[David A. Goldfarb]

As I understand the situation at Ilford with Pan F, when the film was last reformulated, it worked with roll film base, but didn't with the sheet film base (perhaps due to some chemical interaction between the subbing for the base and the emulsion or maybe the coating speed has to be different for different base thicknesses--some technical reason along these lines), and the market for Pan F in sheets (which I would really love to have myself) wasn't large enough to justify the additional research required to adapt the Pan F emulsion to the sheet film base. So I don't think it's harder, per se, but that the film would be first developed for the most obvious market (smaller formats), and then it would be a matter of seeing how easy it would be to adapt it for other uses.

 

[keithwms]

I don't see why it would be harder, it's just inherently more of a financial risk to roll out a product that isn't in high demand and which may thus sit on the shelves to the point of expiration.

There are, of course, slow sheet films like the orthos but these are used more for duping than direct shooting.

The slowest I've used for LF b&w was 5x7 tmax100, though I decided that it was more valuable as a duping film. Fp4+ gives me absolutely no reason to go slower in 4x5 and larger and the extra stop of speed does come in handy. Personally, I've not seen any reason to go pyro with ~ISO 100 sheet films 5x7 and larger, I've only been interested in that for the small (3.25") sheets. Then again I don't enlarge to billboard size like some people! And apparently my eyes aren't so discerning.... (slight sarcasm)

There is of course velvia 50, perhaps the slowest colour sheet film available in all the standard sizes... 64T is another notable slow LF sheet film still available. Both these E6 films can enlarge spectacularly and I have been playing with enlarging them to larger b&w sheet film.

And referring to the massive dev chart, there are plenty of slowish films that can be pulled a stop or two...

 

[Ian Grant]

Perhaps we are overlooking the obvious.

In the 20's and 30's as films improved their speeds increased, demand was for higher speeds and increased quality to make hand held photography more practical. So a modern 125 ISO emulsion like FP4+ is the equivalent of the 1930's Selo FP (Fine grain Panchromatic) of about 28 ASA.

Even in the few years I've been using film there has been a very significant increase in the quality of emulsions and the latest Tmax400 is vastly superior to the FP3 125 ASA film I started with.

Ian