EFKE PL100 Reciprocity?

[RF]

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]

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]

"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]

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]

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]

If you want to use the x^y method, try Metered^1.55=Exposure Given.

[Patrick Ingram]

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]

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