Infrared Film Reciprocity Failure Tests

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Just putting this here for information really. No idea if anyone will find it useful...

I've done a bunch of testing with some IR film and a Zomei 10 stop 720nm deep red IR filter.

I totally screwed up the SFX test to get any serious results, but based on what I did get and a bit of guesstimation, I was quite surprised to discover that the Ilford datasheet is probably right about raising your base exposure to the power of 1.43 Just putting it here so that perhaps @ChrisR can check his app to see if it says the same.

Base Exp : +10 Stops : Ilford SFX 200
1/250............ 4s ............ 8s
1/125............ 8s ............ 20s
1/60 .......... 15s ............ 1m
1/30 .......... 30s ............ 2m
1/15 .......... 60s ............ 6m

And here's the Rollei results. Basically took a range of exposures from a base starting point (Base exposure, then filter on and +10 stops at +0, +1, +2 & +3)

Base Exp : +10 Stops : Rollei 400 IR
1/250............ 4s ............ 8s
1/125............ 8s ............ 20s
1/60 .......... 15s ............ 45s
1/30 .......... 30s ............ 2m
1/15 .......... 60s ............ 6m

I'm actually quite surprised by how close they both are. Which is handy because it's less to remember. The Rollei 400 IR has a ton of latitude, so you could easily just arbitrarilty slap 2 stops on anything over a 4s base time and be done.
 
Just putting this here for information really. No idea if anyone will find it useful...

I've done a bunch of testing with some IR film and a Zomei 10 stop 720nm deep red IR filter.

I totally screwed up the SFX test to get any serious results, but based on what I did get and a bit of guesstimation, I was quite surprised to discover that the Ilford datasheet is probably right about raising your base exposure to the power of 1.43 Just putting it here so that perhaps @ChrisR can check his app to see if it says the same.

Base Exp : +10 Stops : Ilford SFX 200
1/250............ 4s ............ 8s
1/125............ 8s ............ 20s
1/60 .......... 15s ............ 1m
1/30 .......... 30s ............ 2m
1/15 .......... 60s ............ 6m

And here's the Rollei results. Basically took a range of exposures from a base starting point (Base exposure, then filter on and +10 stops at +0, +1, +2 & +3)

Base Exp : +10 Stops : Rollei 400 IR
1/250............ 4s ............ 8s
1/125............ 8s ............ 20s
1/60 .......... 15s ............ 45s
1/30 .......... 30s ............ 2m
1/15 .......... 60s ............ 6m

I'm actually quite surprised by how close they both are. Which is handy because it's less to remember. The Rollei 400 IR has a ton of latitude, so you could easily just arbitrarilty slap 2 stops on anything over a 4s base time and be done.

Interesting! I put the SFX exposure times into Reciprocity Timer, assuming they were metered times, no filters, no exposure compensation, no bellows factor (just to make it work). It gives me the results:

4s ............ 8s
8s ............ 21s
15s ............ 51s
30s ............ 2m 21s
60s ............ 6m 41s

I reckon the differences from your results are less than a third of a stop, ie bang on! Great job of testing there...
 
Not sure I'll ever use this Ian, but respect where it's due for the scientific approach. :ty:
 
:agree:
 
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