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Re: Reciprocity Factor (Ilford)

Posted: 12 Nov 2021, 12:13
by Mick Fagan
Walter, you mentioning David Vestal brought back quite few memories of many magazine articles I somehow managed to read; usually in the local library as I couldn't afford American photographic magazines at the time.

Quite the print worker and I clearly remember a mammoth testing program he did on B&W papers and the major differences between graded paper and multigraded papers.

Well it may be raining all the way to Sydney, but I definitely know it is raining like crazy down here, flooded streets and trees down everywhere. I met up with three people yesterday and we discussed the recent big storms, one lost power for 6 days, the second power and gas for 9 days while the third lost power for almost 2 days. We also lost power, but we are fortunate enough to have house batteries and we weathered the storm unscathed.

Back to the testing, the Bergger Panchro 400 is looking good, but I don't think I'll use it, normal development D76 1:1 17 minutes at 20ÂșC, however FP4+ is looking really good with a half stop developer increase and using Ilford's reciprocity formula. This chart which is really a factor chart, leaves drawn charts for dead. So easy to use, providing one has a mobile phone calculator and uses the appropriate formula, you're in business.

Metered time of 5 seconds, corrected time of 7.598051.... I used 8 seconds and just for once I remembered to pack my Seiko stop watch which I picked up last century when the local primary school switched over to electronic stop watches for $2.00; mechanical marvel.

As for stand development, not really a fan of it. I had a brother who extolled the virtues of stand development in the 70's and he tried hard to get me to give it a go. I did and I don't think I've used it since.

Re: Reciprocity Factor (Ilford)

Posted: 29 Dec 2021, 09:09
by Mick Fagan
Well due to (almost) forseen conditions, the proposed gathering didn't take place, so no photographing the building. There is always next year..... :)

Just as a matter of interest, I did a long exposure using FP4+ with a metered exposure of 8 seconds. Using the Ilford calculation factor from their chart the corrected time is 13.7370469...... I used 14 seconds. Pretty good negative ensued, so this Ilford reciprocity compensation chart seems to be very good. Which it should as it comes straight from the horses mouth, but sometimes one wonders.

Maybe next year I'll get a go and possibly post something?

Re: Reciprocity Factor (Ilford)

Posted: 01 Jan 2022, 13:01
by Walter Glover

Given the definitive time calculation I gather you used the stated P factor of 1.26 and calculated? I'm looking at using XP2 Super with the suggestedd P factor of 1.31. Nice to get a clue that it's within coo-ee. At least Ilford advise the factor whereas Kodak suggest you burn some film testing.

Frohes neues Jahr!

Re: Reciprocity Factor (Ilford)

Posted: 01 Jan 2022, 13:19
by Mick Fagan
Walter, I think their reciprocity chart is one of the best things for the film photographer to have in their arsenal, so easy. I have a friend who doesn't have access to the web or anything like that, he pretty much uses HP5+ in 35mm format.

I gave him the formula for HP5+ in very large written format as he is legally blind. I know that he used it successfully for HP5+ for an approximate metered time of 6 seconds on his inbuilt camera meter then switching to manual and the corrected time he had very good success.

I thought about the XP2 factor and wondered if that would work for normal C41 film, maybe not with three and in some instances four layers of different emulsions on the film; but one never knows.

Ein Gutes Neues Jahr to you too! :D