View Full Version : Reciprocity calculation for Delta 100 and Delta 400

18-Dec-2008, 11:19
A while back I found on these forums (or APUG) a nifty calculation for reciprocity for FP4 and HP5 (same calculation) that made the use of a table unnecessary, and is more specific. Does anybody have one for D100 and D400? I have one for Tmax 400- would D400 be the same, being a tabular grained film? I thought speed would enter the equation, but apparently not for FP4/HP5.


18-Dec-2008, 22:40
Have a look on Ilford's website. They have reciprocity graphs for all of their films. Someone had commented that the "one size fits all" Ilford graphs were not reliable. I asked the question on Ilford's website, and the reply was that Ilford's engineers stood by the graphs. So, if the calculation you have works for FP4+ and HP5+, check the graphs to see if they're similar enough to also work for D100 and D400.
I can't find the question and answer quickly, but Ralph Barker (who I think is a moderator here) is also involved with the Ilford site and was the one who got the info for me from Ilford.

18-Dec-2008, 22:54
Here is the website. Click on technical information, then the films you're interested in. They are PDF files containing the reciprocity graphs.


19-Dec-2008, 14:27
Well, I'm stumped then, because the graphs are all identicle for FP4, D100 and D400. I used the calc for FP4 for D100 for the same scene, same time, same filtration and the neg was at least 2-3 stops over exposed on the proof sheets. I've not used D100 before so there may be a flaw in my system, but I'm pretty confident in my proof time. That leaves my EI (I'm using 50) or dev time. I was confident in both until I saw these negs proofed..... I was hoping that the Delta films had a reciprocity similar to TMax (much better), thus explaining my overexposure.

19-Dec-2008, 21:31
Sorry I don't have an answer, but perhaps if no one else has an explanation you can ask at the Ilford website. I believe Ralph Barker, the moderator there, has access to the Ilford technical people.


Joanna Carter
20-Dec-2008, 01:35
I moved from Delta 100 to Fuji Acros because I wanted to use Quickloads and found that Acros had a much flatter reciprocity curve. Since Delta 100 and Acros are both T-grain films, maybe the Acros curve would be a better fit?

Michael Rosenberg
20-Dec-2008, 10:09
You will have to test the film/developer combination to determine reciprocity correction. I found that for D100 I needed no reciprocity correction up 4 min. when developed in XTOL (1:2 dilution). This differs from what Howard Bond published in PT some time ago; Patrick Gainer expanded on what Howard had found and published in PT and on the UnBlinkingeye web site. On my tests I photographed in my studio using ND filters to get longer exposures.

I have also heard that Acros does not need reciprocity correction in XTOL (1:2) up to 2 minutes.

I found that TMY2 uses the same reciprocity correction for 100T in XTOL (1:2).