# Thread: Reciprocity calculation for Delta 100 and Delta 400

1. ## Reciprocity calculation for Delta 100 and Delta 400

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.

Tim

2. ## Re: Reciprocity calculation for Delta 100 and Delta 400

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.

3. ## Re: Reciprocity calculation for Delta 100 and Delta 400

Here is the website. Click on technical information, then the films you're interested in. They are PDF files containing the reciprocity graphs.

http://www.ilfordphoto.com/products/...essional+Films

4. ## Re: Reciprocity calculation for Delta 100 and Delta 400

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.

5. ## Re: Reciprocity calculation for Delta 100 and Delta 400

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.

http://www.ilfordphoto.com/photocomm...um/default.asp

6. ## Re: Reciprocity calculation for Delta 100 and Delta 400

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?

7. ## Re: Reciprocity calculation for Delta 100 and Delta 400

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).

Mike

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