Looking for low reciprocity failure 35mm B&W film for daytime long exposures

[Eggvillan]

I know that Acros was the king.... but im just getting started with trying this out, and i'd prefer to (a) pay less than $15 a roll, and (b) become familiar with something that is still produced.

I'm getting various ND filters, and (i think) i understand the basic process... but then there's the reciprocity failure issue to deal with. If im looking to take exposures of a minute or more, what should i be using? I've seen really mixed recommendations, and im having trouble finding understandable charts for different films. Right now im leaning toward Tmax 100, but i cant find a reliable chart, and thought i'd ask the community for advice.

i mainly shoot on tri-x 400, but i know that it has terrible reciprocity issues.... help!

 

[Nodda Duma]

Acros was pretty much it for good reciprocity in B&W

 

[Tom Kershaw]

I would have thought T-Max 100 or ILFORD DELTA 100 could be made to work well.

 

[Europan]

The Schwarzschild or reciprocity function is sometimes plotted as a curve.
You have the energy amounts needed for equal density on the ordinate and a time scale on the abscissa.

Seen that?

 

[Svenedin]

Ilford have published reciprocity data for their films and I have found them very good. You do need a scientific calculator but if you have an iPhone the scientific calculator is found by launching the calculator app and holding the phone in landscape orientation.

https://www.ilfordphoto.com/wp/wp-content/uploads/2017/06/Reciprocity-Failure-Compensation.pdf

 

[Old-N-Feeble]

The thing about reciprocity failure is, though the exposure can be compensated for, the contrast increases. This may be of benefit or detriment. Too, who wants to wait an hour when another film will record the image in 10 minutes? If contrast must be compensated for and development significantly decreased then sensitivity decreases a bit also. Then even more exposure is necessary. It's far simpler to use a film like Acros. It's a damn shame it's no longer available. My guess is remaining stocks of Acros will skyrocket in value.

 

[removedacct1]

T-max 100 is pretty good as far as reciprocity goes. For example, 30 seconds becomes 49 with reciprocity factored in. That's very reasonable.