Fomapan 100 reciprocity: excessive.

I've got an app for calculating reciprocity for long exposures, and in general it gives me accurate data. However, when it comes to Fomapan 100, it's way off. If I use the values it suggests, I get severely overexposed negatives. Like, 2-3 stops overexposed. I've often seen these values quoted here on Photo and elsewhere, and the app I use gives these exact same values.

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

I had measured a scene two days ago, giving an exposure of 15 seconds at f16. I made two exposures on 5x7" Fomapan 100: one for 2 minutes and one for 3 minutes. Both were severely overexposed. I could barely get a usable image out of the 2 minute sheet. (It took a lot of post processing tweaks to get this.)

So, the example times posted above were found here on Photo nine years back. Do any of you know if there are updates to the Fomapan 100 reciprocity data that are more accurate? Thanks.

@Ian Grant reported earlier that the reciprocity failure is nowhere near what even Foma themselves suggest. Hopefully he can chime in here with more details.

miha said:

@Ian Grant reported earlier that the reciprocity failure is nowhere near what even Foma themselves suggest. Hopefully he can chime in here with more details.

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Glad to know it's not just me effing something up, thanks. I hope Ian has something to offer.

retina_restoration said:

Do any of you know if there are updates to the Fomapan 100 reciprocity data that are more accurate?

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No, but like you, in my experience the reciprocity failure is overstated in the documentation. I've never done really long exposures on this film; up to a minute or two at most. It's been a while, but I would usually apply a correction of 1-2 stops at most.

I've always found reciprocity correction a bit of a moving target anyway, since the is strictly speaking not even across the frame. The high values suffer less than the low ones, so IMO a reciprocity correction would ideally take into account on which values the emphasis is in the image.