Surely reprocity adjustments are more easily controlled by adjusting the exposure time rather than changing the apature. I know I'm new to LF but that's how I have been managing it with MF cameras for as long as I can remember.
Perhaps I'm missing the point here?
Anyone used Fomapan sheet film?
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richard littlewood
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Rob. I reckon you are right to use extended times with reciprocity. All that f22 vs f4 with the same time stuff is right also. I'm usually an FP4/Delta user, and I like to think I have reciprocity under control with MF and LF, but using a different film - as I am going to do now with Fomapan - means doing sodding tests! Why I'm putting myself through it, I dont really know - especially as the Foma seems to need longer times in that area.
Reciprocity is a ticklish issue, and I've been after some Foma advice on the web - Ian seems to be looking into this, and this weekend I am too, and I'll probably run through half a dozen sheets and establish a few workable times and let it be known what I've found out. It's a shame film makers dont do more scientific tests themselves - I mean Ilford and Foma reciprocity times all seem open to question. It wouldnt take much for them to publish a decent set of findings under a few different circumstances, rather than the set figures that can be totally misleading as no one is sure how they arrived at their figures.
I know film users are supposed to test and test their materials, and most of us do, but film makers are in a great position to ease that particular path.
Enough of this ranting, I'm off out to enjoy a bit of sun!
Happy Easter!
Reciprocity is a ticklish issue, and I've been after some Foma advice on the web - Ian seems to be looking into this, and this weekend I am too, and I'll probably run through half a dozen sheets and establish a few workable times and let it be known what I've found out. It's a shame film makers dont do more scientific tests themselves - I mean Ilford and Foma reciprocity times all seem open to question. It wouldnt take much for them to publish a decent set of findings under a few different circumstances, rather than the set figures that can be totally misleading as no one is sure how they arrived at their figures.
I know film users are supposed to test and test their materials, and most of us do, but film makers are in a great position to ease that particular path.
Enough of this ranting, I'm off out to enjoy a bit of sun!
Happy Easter!
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IanG
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I wasn't suggesting the same light levels in my example, rather how there's potential for big discrepancies in Reciprocity tables.
Conventional wisdom, in articles & books etc states that reciprocity can be partially avoided by using a wider aperture - i.e. Using an 1/8th @ f5.6 instead of 4 seconds @ f32 - same overall exposure avoids reciprocity. Howard Bond's article is testing with a step wedge and he's varying aperture against shutter speed
So the theory is that reciprocity is dependent on the choice of shutter speed/aperture used as well as the light level.
But in practical situations the spectral quality of the light can also change at low light levels, so this is another variable, and then there's the effects of filters etc.
The initial tests I made were at EV6 (350 lux) and EV3 (44 lux), I chose these levels because they are on the low side of the typical daylight & artificial light levels found in most buildings. EV3 required a 100watt bulb to be turned down on dimmer switch. These tests were made for a specific project being undertaken by by a photography student, new to LF, who is using Fomapan200.
The next tests are at EV3 & EV2 to see the effects of varying aperture with shutter speed, they are developing as I write. Then later some night shots.
Ian
Conventional wisdom, in articles & books etc states that reciprocity can be partially avoided by using a wider aperture - i.e. Using an 1/8th @ f5.6 instead of 4 seconds @ f32 - same overall exposure avoids reciprocity. Howard Bond's article is testing with a step wedge and he's varying aperture against shutter speed
So the theory is that reciprocity is dependent on the choice of shutter speed/aperture used as well as the light level.
But in practical situations the spectral quality of the light can also change at low light levels, so this is another variable, and then there's the effects of filters etc.
The initial tests I made were at EV6 (350 lux) and EV3 (44 lux), I chose these levels because they are on the low side of the typical daylight & artificial light levels found in most buildings. EV3 required a 100watt bulb to be turned down on dimmer switch. These tests were made for a specific project being undertaken by by a photography student, new to LF, who is using Fomapan200.
The next tests are at EV3 & EV2 to see the effects of varying aperture with shutter speed, they are developing as I write. Then later some night shots.
Ian
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IanG
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Surprisingly the 2nd test shots show remarkably little difference between the EV3 shots, which ranged from 2 seconds @f4 through to 1 minute @ f22
In fact Fomapan 200 seems to be behaving almost like Tri-X in Howard Bond's tests.
At EV2 @ f22 the correction needed was 1 stop, 4 minutes instead of the metered 2 minutes. The film is used at 100 EI and developed in Pyrocat HD 1+1+100 for 12 minutes @ 20°C. Metering was with a Pentax Spotmeter V and checked with a Profisix SBC.
Ian
In fact Fomapan 200 seems to be behaving almost like Tri-X in Howard Bond's tests.
At EV2 @ f22 the correction needed was 1 stop, 4 minutes instead of the metered 2 minutes. The film is used at 100 EI and developed in Pyrocat HD 1+1+100 for 12 minutes @ 20°C. Metering was with a Pentax Spotmeter V and checked with a Profisix SBC.
Ian
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Jonathan Perkins
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richard littlewood
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Just a quick up-date. Did a test with Fomapan 100, and found it iso 50, and dev'd in ID-11 1+2 in a Jobo for 8 mins, whereas I would do FP4 iso 80 for 10.5 mins. Very decent negs, and not unlike FP4. Not tried it yet in really contrasty light, like full sun, but I imagine reducing development a little there. Also did a metered 30 sec exposure (daylight with nd filters) and the best neg was exposed for 1.5 mins, dev'd for 8 mins, with no nasty contrast issues. It's decent stuff.