Using Formapan 400 for 20 second+ Exposure ???

BADGER.BRAD

BADGER.BRAD

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Hello Everyone,

Right before anyone points out the obvious yes I know my camera/film combination is not great but two things, I have some Formapan 400 120 film and only two cameras to use it in a 1931 Kodak Box Brownie and a Holga. I will be doing this for just a bit of fun along side using digital. I'm thinking the Box Camera !. I Exposure will be something like 15 to 20 seconds so is there a rule of thumb IE: 2/3 times exposure. I will of course try a few exposure times. The shots will be wide angle Astro.

Thanks all.
 
Apparently, Foma 400 in 120 has a hilarious reciprocity failure plot.

10 seconds metered requires 50 seconds of actual exposure
15 seconds metered requires 98 seconds,
20 seconds metered requires 137 seconds.

See here, post 5 for full table. Not sure if this is official, but it's the first credible result I could find :)
 
Thanks for that Jonathan,I had hears it was quite bad but have never really done long exposure with film at all, the table should at least give me an idea !
 
Just have fun with it, sometime reciprocity can be useful, a bit like adding a ND filter
 
I always find "add two to three stops" if you get into long duration exposures works quite well.

The times look silly, but when you're considering a doubling of time each... time... 20 to 137 (using Jonathan's example above) is about 2.5 stops, with 80 seconds to 160 seconds representing just one stop of light - which isn't that much considering it's over a minute duration. If you have a film with good latitude (no experience with Foma 400) you can get fairly rough & ready with it.
 
Foma reciprocity is a joke as indicated above, I have tried and it really does need those very long times, I suggest shooting what you have in better light.
 
I would do as much research as you can & then bracket it & write down the details for each exposure.

That's what I've done with some old 35mm Agfa? stuff but I've not yet finished the roll to see how the shots turned out. That was star trails. The best I could find was 'similar' films which suggested to double the exposure so that's roughly what I done.
 
LeeRatters said:
suggested to double the exposure
Click to expand...
IME it's not that simple, especially for >5s exposures. Most reciprocity curves are some power of exposure time so whilst for short times there is not a huge difference, by the time you get up to 20s for Forma 400 the exposure is nearly 7x the metered value. Even something like FP4+ is starting to deviate from doubling at >20s and below 5s needs quite a bit less than double.
 
BADGER.BRAD said:
Hello Everyone,

Right before anyone points out the obvious yes I know my camera/film combination is not great but two things, I have some Formapan 400 120 film and only two cameras to use it in a 1931 Kodak Box Brownie and a Holga. I will be doing this for just a bit of fun along side using digital. I'm thinking the Box Camera !. I Exposure will be something like 15 to 20 seconds so is there a rule of thumb IE: 2/3 times exposure. I will of course try a few exposure times. The shots will be wide angle Astro.

Thanks all.
Click to expand...

sirch said:
IME it's not that simple, especially for >5s exposures. Most reciprocity curves are some power of exposure time so whilst for short times there is not a huge difference, by the time you get up to 20s for Forma 400 the exposure is nearly 7x the metered value. Even something like FP4+ is starting to deviate from doubling at >20s and below 5s needs quite a bit less than double.
Click to expand...

Well I went by a bit of Google & the details on the Lightmeter App in the Reciprocity Calculator part. I have the settings saved & have bracketed so when developed I should have an idea.

The App also lists Fomapan 400 - it says a 15 second exposure needs to be 1m 38s which a 2.7 stop adjustment. 15 minutes needs a plus 2.9 stop adjustment. Strangely enough, when you get up to a silly 3 hour exposure, it only needs a 2.1 stop adjustment and longer exposures from that drop even more.
 
sirch said:
Foma reciprocity is a joke as indicated above, I have tried and it really does need those very long times, I suggest shooting what you have in better light.
Click to expand...
I agrre with at. But long exposures are not impossible, a couple of hours?
 
I always treble the time with foma at least. It's a film you just cant over expose.
 
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