Differences in roll film/sheet film emulsions

[John Kasaian]

I'm curious as to why and what the differences are between like named emulsions for roll and sheet films. For example, the 'old' Tri-X sheet film was rated by kodak as iso 320, in 120 you could get either iso 320 or 400 and in 35mm only 400. I am curious because I just shot a roll of (new)tmax 100 in the family Olympus Stylus and WOW! I know tmax 100 sheet film has been used by some well respected photographers and am curious about the differences, if any, between the roll and sheet films having the tmax 100 handle before I throw caution to the wind and get yet another box of that expensive yellow stuff to play with. My question then, is: What difference is there between the roll and sheet versions of the new tmax 100? Anyone have a theory?

[Huib]

John,

I believe Tri-X is one of the last emulsions that is (or better: was) sold in two variations: the film labeled 'Tri-X' (400ASA) and 'Tri-X Professional' (320ASA). They share the same name but the emulsion is quiet different!. The Pro version has a long toe section.

AFAIK there are no differences in other emulsions (TMX/TMY/FP4/HP5/Delta 100, etc) between 35mm, roll and sheetfilm.

Huib

[Carl Weese]

You could try asking at the Kodak web site, but my impression is that TMax films are the same in roll and sheet versions. Tri-X is not just different in ei rating, the whole curve shape is radically different for the two films. Ilford films are consistent in roll and sheet versions, so at this point Tri-X may be the only film where this roll/sheet discrepency still exists.---Carl

[Mark Farnsworth]

Kodak says that TMAX developer should not be used with TMAX sheet film, and that TMAX-RS developer should be used instead. Maybe the emulsion is the same (I really don't know) and there are some chemical differences in the film base.

[Richard Knoppow]

Tri-X film is still sold in two different emulsions. The sheet film is very different from the roll film and 35mm version. Plus-X was the same but the sheet film version has been discontinued. I don't know why Kodak decided to market two very different films under nearly the same name other than they like to keep up trade names. T-Max emulsions seem to be about the same in all formats. Tri-X and Plus-X sheet film is very long toe film. The characteristic curve is upswept all along its length leading to exagerated highlight contrast. The roll film versions are medium toe general purpose films. Both Plus-X emulsions were avilable in 120 film under slightly different names. In years gone by Kodak has always had a long toe film available in sheet film, usually billed as a portrait film, but with different names than general purpose films of the same speed. Another confusion are the T-Max developers. These have nothing to do with T-Max film. Some people thought you had to use T-Max developer with T-Max film. Actually, both are general purpose developers and T-Max film can be developed in virtually any standard developer. One would have to get into the heads of Kodak's marketing people to know why they decided on creating all this confusion.

[John Kasaian]

Mark Farnsworth's observation that Kodak recommmends Tmax RS developer rather than Tmax for sheet Tmax(confusing, eh?) is what has me scratching my head. AFAIK, Tmax 400 film---the only Tmax sheet film I'm familiar with--- does nicely in D-76 which goes along with Richard Knoppow's statement. Perhaps Tmax developer isn't recommended for sheet film because of dilution, shelf life or other issues. Tmax RS is, I believe, the replenisher for Tmax developer so maybe it has more "oomph" in it to get depleted Tmax cooking again and this helps with sheet film development? What I know is that the new Tmax 100 35mm roll film in Tmax developer sure impressed me and I'd like to try to duplicate the results with sheet film if possible. Thanks for all the responses!

[neil poulsen]

I've called Kodak regarding TMax 100, Ilford regarding HP5, and Fuji regarding Astia, and all three say that there is no sensitometric differences between medium format roll film and sheet film for any of these products. The emulsions are the same, and there is a slight difference in the mylar base. But, this difference isn't enough to see in densitometer readings.

However, there is a significant difference between sheet film or medium format film when compared to 35mm film. 35mm film has a substantially thicker base that gives it a higher film-base plus fog level.

To save money, my method of developing sheet film and medium format film are identical. So, I use medium format film for all my calibrations.

As for recommending TMax original developer for medium format TMax 100 and TMax RS for sheet film, because of the differences in physical dimensions only, sheet film has a tendency to form a destructive discoloration when developed in the original TMax developer. The emulsions for these two films are identical. In fact, I was told by the technician who brought this problem to Kodak's attention, that this was the reason for formulating TMax RS. This discoloration can be scrubbed off. But if not scrubbed and the film dries, the damage becomes permanent.

[John Kasaian]

Thanks Neil! Another mystery solved! Thanks to all who responded!