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Ronan
17-Jan-2024, 11:41
Hello Kind people of LFP! I am shooting a new project tomorrow with a 47mm xl on my ebony SV45TE. I have a centre filter IIIc 4x. Can you tell me how many stops to compensate using this with 160 Portra and im using a flash. THANK YOU!
Michael R
17-Jan-2024, 11:55
Schneider’s indication for the IIIc is 2 stops. Incidentally that’s what 4x means.
Ronan
17-Jan-2024, 12:50
Schneider’s indication for the IIIc is 2 stops. Incidentally that’s what 4x means.

THANK YOU!!!

So I rate 160 film at 50iso?
Corran
17-Jan-2024, 13:08
40, or perhaps 25-32 as many rate Portra more like 100-125 EI.
Ronan
17-Jan-2024, 13:13
40, or perhaps 25-32 as many rate Portra more like 100-125 EI.

Thanks! yes i usually rate it about 100!

gent!
phdgent
17-Jan-2024, 23:33
Here are some technical publications by Schneider:

245681
245682
Ronan
18-Jan-2024, 14:32
40, or perhaps 25-32 as many rate Portra more like 100-125 EI.

just double checking, I did a test on my digital camera, 100iso it lowest it goes. I have to fire my flash 1200w twice to get the right exposure at F22. So if i want to expose at 25iso to compensate for my filter I pop the flash 8 times? Thank you
Corran
18-Jan-2024, 14:42
That should be correct. No reciprocity issues like film.
Ronan
18-Jan-2024, 16:34
That should be correct. No reciprocity issues like film.

Well i am shooting film but i dont think you get reciprocity with flash as I am filling it with short bursts of light?

Thanks all again, the stress shooting sheets that cost almost 20 euro each now!

:(
Kiwi7475
18-Jan-2024, 18:47
Well i am shooting film but i dont think you get reciprocity with flash as I am filling it with short bursts of light?

Thanks all again, the stress shooting sheets that cost almost 20 euro each now!

:(

Actually reciprocity failure happens both on long and on very short exposures. However modern films only exhibit issues on the short end when the exposure is below ~1/5000 second, most even less than that, so you should be fine with a flash unless you’re using really exotic, very high speed flashes.
Ronan
19-Jan-2024, 13:01
Actually reciprocity failure happens both on long and on very short exposures. However modern films only exhibit issues on the short end when the exposure is below ~1/5000 second, most even less than that, so you should be fine with a flash unless you’re using really exotic, very high speed flashes.


This is very technical information thank you! Hope the exposures were ok, shot ten sheets pretty much blind. I did my best! :)