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Old 26th November 2019, 06:33 PM
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Martin Aislabie Martin Aislabie is offline
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Default Is anyone using Ilfords new receprocity formula ?

Hi guys

Has anyone else any experience with using Ilfords new reciprocity formula ?

Actual exposure = x^y

Where X = straight meter reading

And Y = exposure factor

HP5 = 1.31
FP4 & Delta 10 = 1.26
Pan F & D3200 = 1.33
Delta 400 - 1.41

I have been using the new exposure calculation on some seascapes on HP5 and have ended up with some surprisingly long exposure times resulting in reasonably dense negatives.

I was wondering what other peoples experience has been ?

Martin
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Old 26th November 2019, 07:14 PM
alexmuir alexmuir is online now
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I’ve tried it, but the results I get from the calculation seem to be quite short compared to the old recommendations. For HP5, 4 seconds equates to 6, and 10 to 20.
I’m not great at keeping notes, but I developed a roll of 120 HP5 last week which had a couple of indoor still life shots. They were certainly exposures of over 1 second, and most likely in the range of 4-10 metered. The exposures were corrected on the new basis, and the negatives look fine. The film speed used was 400 with the negatives developed in ID11 for the recommended time.
Alex


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Old 26th November 2019, 11:37 PM
Svend Svend is offline
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Hi Martin,

Is the new formula you're referring to the same as what was discussed here last year?
http://www.film-and-darkroom-user.or...iprocity+chart

There isn't anything more recent than that, is there?

I did use Ian's chart (post #7) last weekend for a roll of FP4, but haven't developed the film yet. Won't be long, and I will report back and let you know how it turns out. Initial impression was much like yours -- some very long exposure times. I didn't keep notes as it was a sketchy place to shoot -- downtown Detroit, abandoned factory....we weren't lingering too long, as you can imagine... Hope the film turns out.
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Old 27th November 2019, 08:46 AM
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I've used it with a roll of HP5 Plus and it seems to work fine.

Bill
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Old 27th November 2019, 09:15 AM
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I used it shortly after it was announced some time ago and found it worked just fine. When I need to use it again I will take some notes to be sure.
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Old 27th November 2019, 09:22 AM
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I posted a graph of Ilford's new data here

Ian
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Old 27th November 2019, 09:27 AM
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In your graph, Ian, I take it the black line is the old general recommendation from Ilford?
Alex


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Old 27th November 2019, 10:15 AM
Lostlabours Lostlabours is offline
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Yes, that black line is the old recommendation. I've added it here as it's relevant.



It's worth remembering that all films actually have two ISO speeds Daylight and Tungsten, FP4+ is ISO 125 Daylight, ISO 80 Tungsten. This also affects exposure in some lighting conditions where thee light colour temperature has dropped, (warm evening sunlight).


Ian
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Old 27th November 2019, 10:49 AM
Anon01 Anon01 is offline
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OK, Can I ask a question please is it relevant to me.

I am used to shooting digital, with a lee big stopper which needs an extra factor of 10 for exposure, in other words

A shot of a normal 1/60th will be 15 seconds etc.

How will I calculate it then using Ilford FP4 or HP5 please remember I am NOT technical


??????? are these right to use

https://mkaz.com/film-reciprocity-tables/

https://apps.apple.com/gb/app/recipr...er/id459691262

https://play.google.com/store/apps/d...ocity&hl=en_GB

Thanks



.
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Old 27th November 2019, 11:36 AM
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If you type “reciprocity timer” in the App Store’s search function it’ll bring up an app that does the calculation for you according to film type. If you look for “Lee filters” in the App Store it’ll show you a calculator that works out the exposure for the big stopper.

I haven’t used either so can’t recommend them but they look handy.

Hope that’s of some help.


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