I have just uncovered my Cokin IR (opaque red) filter. Can anyone remind me how many stops should I allow when using this. I seem to remember something like 8 or 10. It will be on Ilford SFX Film nominally rated at 200ISO.
Hi John, is that the Ilford dedicated SFX filter? If so, I got very good results with +4 stops. Mind, I suppose it depends how you dev the film. I used D76 for 10.5 mins 1+1. Good luck.
I bought the film at the same time as the filter as a special offer and they came bundled together. The filter mount is embossed Cokin but the filter itself is a gelatine sheet. I used it a while back and have forgotten how many 'stops' to allow. I seem to remember 6 or 8 but I may be mistaken. I also remember developing it 1-1 in ID11 for the time recommended by Ilford. That worked out fine for me.
Yep, you're using the SFX filter. Mine also came bundled with a roll of SFX. The SFX tech sheet gives a filter factor of 16(4 stops). I got my dev. times wrong. I actually used Ilford's recommended time for D76 of 14.5 mins 1+1.
Filter factor of 16? Well in old money that should be 8 stops! An ordinary yellow filter with a factor rating of 2 was one stop. An orange with a factor of 4 was 2 stops. A red (normal not IR) was 6 = three stops so 16 should be 8 stops. Or is there something I have not taken into account?
Hiya John. Filter factors double up for every 1 stop increase. Filter factor 2 = 1 stop 4 = 2 stops 8 = 3 stops 16 = 4 stops
