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Old 23rd October 2019, 06:53 PM
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DaveInElland DaveInElland is offline
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Default Fomapan 400/100 Reciprocity

I’ve just been looking at the reciprocity table provided with my Fomapan 400120 film

Exposure (seconds) 1 Lengthening of exposure 1.5x
Exposure 10secs - 6x
Exposure 100 secs - 8x

Not a great deal of information and not very nuanced either. I find it difficult to understand that 1 9 seconds becomes 13.5 and then 10 seconds becomes 60!

Clearly I’m missing something here so does any one have any experience of reciprocity failure with Fomapan 400 or indeed F100?

TIA
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Old 23rd October 2019, 10:42 PM
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Dave, haven't used F400, but the reciprocity failure on Fomapan 100 is not linear- it just falls off a cliff. I found a good chart which I printed and laminated for my bag.
I'll try to find the link, but basically:
Metered Required
1s 2s
5s 20s
10s 80s
30s 5mins
1min 12mins

I work in low light quite a bit, and Fomapan's reciprocity chracteristics can be a challenge. However, treat it as a good news/bad news thing. In poor light, which is often rather flat, different prts of the scene can actually be affected to different degrees. My impression is that it can actully pep up the contrast somewhat.
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Old 24th October 2019, 06:21 AM
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Quote:
Originally Posted by skellum View Post
Dave, haven't used F400, but the reciprocity failure on Fomapan 100 is not linear- it just falls off a cliff. I found a good chart which I printed and laminated for my bag.
I'll try to find the link, but basically:
Metered Required
1s 2s
5s 20s
10s 80s
30s 5mins
1min 12mins

I work in low light quite a bit, and Fomapan's reciprocity chracteristics can be a challenge. However, treat it as a good news/bad news thing. In poor light, which is often rather flat, different prts of the scene can actually be affected to different degrees. My impression is that it can actully pep up the contrast somewhat.
Wow! So I wasn’t being dumb! I guess this would be good for those wanting to play with long exposures then on the upside too? I was doing some more digging last night and the phrase “falling of a cliff” did crop up a few times and as your figures show it’s not linear either.

Thank you - appreciated!
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Old 24th October 2019, 07:23 AM
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This is the table I found and have used with Fomapan 100.



Bill
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Old 24th October 2019, 07:55 AM
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Default Fomapan 400

Thanks Bill, using that title in the search engine also turned up this for 400 film. Excuse the quality, doing this on my phone whilst sat on a wall waiting for one of the grandsons to turn up at school!

FWIW, I was doing some more digging about last night and the consensus over many forums etc is that these are excellent everyday films, have a death defying reciprocity graph but that this can have some benefits in terms of contrast and, ironically, getting longer exposure times for long exposure work.

Thanks as always everyone!
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Old 24th October 2019, 07:59 AM
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Quote:
Originally Posted by Bill View Post
This is the table I found and have used with Fomapan 100.



Bill
Cheers Bill, hope you are well Sir, did you find the times quoted gave reasonable negatives?

One of the other things I noted was that many of the keyboard warriors had fancy algebra but very few were posting anecdotal evidence from real life usage and although this is subjective rather than objective it offers a better feel I think for real life picture making
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Old 24th October 2019, 08:36 AM
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This is one of the things I am going to have to take into account, as I shoot astronomy and this is most interesting
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Old 24th October 2019, 09:48 AM
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Quote:
Originally Posted by DaveInElland View Post
Cheers Bill, hope you are well Sir, did you find the times quoted gave reasonable negatives?
Good Morning Dave, Quite well Thank You.

The negatives I got using the times from the table are fine. FYI I only use Fomapan 100 in my 5 x 4 camera so have littler experience of 120 or 35mm films. I use it while I am getting to grips with the camera but intend to move to Ilford films when I (think I) know what I am doing.

Bill
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Old 24th October 2019, 11:17 AM
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Some years ago I did some practical reciprocity tests with Fomapan 200, I'd already done speed and development tests a year earlier.

My experience was that the reciprocity wasn't as bad as Foma's tables indicate. However what's often forgotten is other issues can cloud reciprocity.

First I shoot Fomapan 100 & 200 at half box speed, and second B&W films actually have two ISO speeds Daylight and Tungsten this can be as much as a Stop with some films.

These days few people use Tungsten lighting but , and few years ago it was quite common to use Tungsten studio lighting and there were Tungsten balanced slide films.

FP4 has a Dalight ISO of 125 and Tungsten ISO of 80, EFKE 25 had a DAylight ISO of 50 and a Tungsten ISO of 25. Ilford no longer list the Tungsten speeds of most of their films but they do state 125 is the Daylight ISO for FP4. The HP5 datasheet alludes to differences in speed with Tungsten lighting in the filter factor section of the 1996 datasheet.


Fomapan 100 & 200 35mm & 120 films have similar spectral response to FP4 so will have a lower EI in tungsten lighting, 2/3rdss of a stop slower in Tunsten lighting.

Now my tests were made in low light (daylight) with a whole roll of 120 Fomapan 200, bracketing in 1/2 stops. I was interested in the 1 second to 10 second range. At one second I needed 1/2 a stop increase and 10 seconds 1 stop increase. that compared to Foma's data of x3 1.5 stops increase at 1 second and x8 3 stops increase at 10 seconds.

However that's in low daylight, with Tungsten studio lighting you need to add in the extra 2/3rds of a stop, and household lighting has a lower colour temperature tahn Studio lighting and that will also increase Reciprocity and then we get into the sorts of figures Foma suggest.

It's best to do some tests, that can be as simple as making some notes and bracketing.

Ian
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Old 24th October 2019, 11:32 AM
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Lostlabours Lostlabours

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Some years ago I did some practical reciprocity tests.................

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I find people like you amazing, I would never have the ability/skill to do such things
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