Heliopan Infra Red filter 695greenspun.com : LUSENET : Large format photography : One Thread
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 (400 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. However this was hopelessly underexposed, in fact there was no image whatsoever. So after a couple of further tests I ended up with 1.1/2min. @ f16 in bright sunlight! Now I know panchromatic material dosen't respond normally to such deep red filters but this was still a suprise to me. Best regards,
-- Trevor Crone (email@example.com), March 30, 2001
Trevor, The thing to remember with infrared film is that it is sensitive to both visible and infrared wavelengths, as you probably know. The SFX film is not a true infrared film, it's red-sensitive, just barely into the infrared region. That 89B filter blocks a lot of visible light (just look through it and you'll see how much), so you would get very little exposure, as you've discovered. If you used Kodak High-Speed Infrared you could work with much shorter exposure times, because the 89B and even the 87C, a visually opaque red filter which looks black, will transmit all the infrared exposure. You can't meter for that with conventional meters. When I've tested Kodak HIE with a variety of filters, I have found that there is only a two or three stop difference between no filter and the 87C, bizarre as that sounds. If you want to know the settings for this combo, I can look up my notes for you. Unfortunately Kodak has stopped making the 4x5 HIE - it's only available in 35mm.
-- Sandy Sorlien (firstname.lastname@example.org), May 05, 2001.
Thanks Sandy. I've just finished testing SFX200 with the Heliopan 695 and I've hand some excellent results. With this filter SFX200 produces true IR effects, white foliage, dark skies and the films sharpness is superb and fairly fine tight grain structure. I found that a five stop adjustment to be about right (in effect this brought the film speed down to about 6 ISO). I was getting exposures of around 3 to 4 seconds at f22 in bright UK sun (important shadow readings was placed on zone 3) I was using the 120 format in 6x9 and 6x12 Horseman backs. I just wish this film was available in 4x5 sheet.
-- Trevor Crone (email@example.com), May 07, 2001.