Fomapan 100 Sheet Film Reciprocity

[IanBarber]

I appreciate there has been lots of talk about this subject but I was wondering just how accurate the Fomapan Data Sheet is when it comes to reciprocity.

15 seconds metered time = 2min 15 seconds, 6 seconds metered = 30 seconds according to their chart. Has anyone gone to town to test these and if so what are your conclusions.

Thanks

 

[Andrew O'Neill]

I have always found manufacturer's data to be a bit over the top. I find it hard to believe that 2:15 is required for 15".

 

[pdeeh]

Ian grant has posted on this very subject. have a search in his posts

 

[IanBarber]

Ian grant has posted on this very subject. have a search in his posts

I thought he had mentioned it but wasn't sure if he actually posted any correction times based on his testing

 

[pdeeh]

use the Google forum search rather than the basic forum search. I can't remember if he posted a set of revised times in detail though.
I've used plenty of Foma and found that recip isn't incredibly bad. I also found the best way to find out was to sacrifice some film to testing.

 

[IanBarber]

How did your times compare to the data sheet on the fomapan website

 

[pdeeh]

as I recall about 4 to 6 or 8 x metered time in dusk or
heavy wooded type light. but I'm relying on memory, plus I am not a zoneista and I don't get worked up about exactitude in exposure.
(I'm trying to say, I'm not a trustworthy source if precision is important to you)

 

[Ian Grant]

I tested Fomapan 100 & 200 for reciprocity a few years ago for a member here who I helped when he used LF for his Photography Degree course. It was nowhere near the official datasheet.

Now I'd tested the true film speeds as being half the box speed and based on that at 1 second reciprocity was 1/3 to 1/2 a stop extra exposure and at 10 seconds a stop. that's worked perfectly for me for 8-9 years I've been using Foma films 120 and sheet film.

With sheet film you need to watch the extension factors as well.

Ian

 

[revdoc]

This film's reciprocity failure is pretty bad. I worked out the required exposure corrections using the following formulae, and they've proved to be bang on.

http://farm8.staticflickr.com/7005/6804638225_1c1356ae7c.jpg

Here are some generic results that will give you an idea of the results of these formulae, where the LHS is metered exposure and the RHS is the corrected exposure:

1s = 2s
2s = 7s
4s = 21s
8s = 59s
16s = 2m 32s
32s = 6m 17s
64s = 15m 15s
128s = 36m 13s

I do a certain amount of pinhole photography, so I've used these for very long exposures, and the "100 seconds max" doesn't seem to apply in this case.