View Full Version : EFKE PL100 Reciprocity?
Does anyone know where I can find a chart that has reciprocity times for this film? I've been simply doubling times for 1 second and longer, but I'm sure it may be more than that the further away I get from 1. Thanks for any help!
David A. Goldfarb
4-Dec-2003, 10:46
Reciprocity is pretty similar for all old-tech panchromatic films (+1 stop for 1 sec., +2 stops for 10 sec., +3 stops for 100 sec.). A reciprocity chart for a film like Tri-X should give you some good starting points.
Modern films like T-Max and Delta films have different reciprocity characteristics.
tim atherton
4-Dec-2003, 11:04
"Modern films like T-Max and Delta films have different reciprocity characteristics"
Although according to the manufacturer the reciprocity characteristics of the Delta films and the older FP4/HP5 are identical?
Michael Kadillak
4-Dec-2003, 11:07
Ilford has a reciprocity curve listed within their webpage for FP4. Since PL100 and FP4 are both old emulsion based products, I recently contacted Ilford and their tech department told me that the following relationship is what they recommend for reciprocity correction:
Corrected Time = Metered Time ^1.48
Raise your meter time to the power of 1.48.
Seems to work well for what I am working with for PL100.
Cheers!
Jim_3565
4-Dec-2003, 13:51
It's been a while since I've done a least squares regression, so I'm not sure how this fits a x^1.48 curve, but this table has proven quite accurate for me. PL100 has a terrible reciprocity charcteristic, so if you're going to be doing a lot of long exposures, I'd use 400TMax.
This table also applies in my experience to both Bergger BPF 200 and to JandC Classic 200.
Meter / Exposure Given (All times in seconds)
1 / 2
2 / 5
4 / 15
8 / 35
10 / 50
20 / 120
30 / 195
40 / 300
50 / 405
60 / 525
70 / 600
80 / 825
90 / 1005
100 / 1200
Jim_3565
7-Dec-2003, 20:55
If you want to use the x^y method, try Metered^1.55=Exposure Given.
Patrick Ingram
31-Dec-2003, 15:33
This is now an old thread, but for what it's worth.... the "+1 stop for >1 sec, +2 stops for >10 sec, etc." works out to 2 x t^1.301, where t is the time indicated by the meter (and "x" means "times"), if you interpolate it in the natural way. You can check that this gives the "right" answer for t=1, 10, 100.
Gary L. Quay
21-Jan-2006, 07:11
I know that this is a really old thread, but in case anyone is interested, jandcphoto.com has the reciprocity times for this film in their tech data section.
--Gary
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