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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.
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.