Speed difference between Acros II, TMX, and Delta 100 at same CI?

[Stephen Benskin]

Process promptly?

I have several studies that show significant speed differences between fresh exposure and film that has sat for several months between exposure and processing.

The test is straightforward. I put a sensitometric exposure on every other roll of film I roll as I load the cassette.

Then before processing I pull a strip of film from the loader and put a fresh sensitometric exposure on it.

Process in the same tank for the same time, I get two completely different contrast indexes and speeds.

The obvious lesson is: Process promptly.

Then you get the most speed and contrast.

The corollary is: give greater exposure and process to higher contrast index if you feel like you might delay processing

Process promptly?

I have several studies that show significant speed differences between fresh exposure and film that has sat for several months between exposure and processing.

The test is straightforward. I put a sensitometric exposure on every other roll of film I roll as I load the cassette.

Then before processing I pull a strip of film from the loader and put a fresh sensitometric exposure on it.

Process in the same tank for the same time, I get two completely different contrast indexes and speeds.

The obvious lesson is: Process promptly.

Then you get the most speed and contrast.

The corollary is: give greater exposure and process to higher contrast index if you feel like you might delay processing.

It's part of latent image keeping. ISO 6 has it in 5.4.1 Conditioning of specimens. "The processing shall be completed in not less than 5 days and not more than 10 days after exposure for general purpose films, and not less than 4 hours and not more than 7 days after exposure for professional films." The old standard had a hold time longer than 2 hours as the effect tends to plateau after a few hours. The standard also stipulates the samples be kept at 23oC +- 2oC at a relative humidity of (50 +- 5)%.

 

[Keith Tapscott.]

Makes sense, Perceptol typically loses a stop in speed, give or take.

He may have gone over to digital imaging now.
I think he used a mamiya rb 67 and a Sinar F 4x5.
The latter he used FP4 Plus at a low ISO rating of around E.I.32-40, again he used diluted Perceptol.

 

[DREW WILEY]

Pan F was designed to accommodate about the same luminance range as color slide film. Yeah, you can tweak the contrast a little during development, but it does best when you seek out subject matter of limited brightness range, or else artificially illuminate it in that manner.

The best developer for Pan F I've used is a special tweak of PMK pyro, rating the film at 25. It's not a particularly versatile film, so I seldom shoot it. But I do have a good number of superb prints made from Pan F 120. It has its own special look.

Acros is quite different, even in spectral sensitivity. Too bad it's no longer available in sheets.