Has anyone used the Heliopan IR filter 695 (Wratten 89B) with Ilford's SFX film? If so could you please give me some indication of an exposure factor.
As a matter of interest I just ran a quick test with some Polaroid Sepia film (4 00 ISO) and the indicated spot meter reading (not made through the filter) gave me an exposure (allowing for Heliopan's exposure factor of x60) of 1/2 @ f22. Ho wever this was hopelessly underexposed, in fact there was no image whatsoever. S o after a couple of further tests I ended up with 1.1/2min. @ f16 in bright sunl ight! Now I know panchromatic material dosen't respond normally to such deep red filters but this was still a suprise to me. Best regards,