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I am experimenting with shooting on infrared film for the first time.

I have IR B&W Rollei 400 ISO film, Canon AE-1 camera, 28 mm wide lens, Hoya R72 filter. Would I set my camera to 400 ISO or what should I set it to? In general, what is the rule of thumb I should follow when using this filter?

Thank you

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I suspect metering will not be useful in that situation. The metering responds to visible light, which the filter blocks. The metering does not respond to infrared, which the filter passes. I think you are on trial and error.

This article (with some experience) says compensate to about 9 stops down

http://www.markcassino.com/b2evolution/index.php/rollei_ir_400_first_impressions

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Perhaps the proper question is, what is the filter factor for the R72 filter. (how many stops of light does x filter block ) i am sure there is a general filter factor known for the filter but i do not know it. I would shoot the film at its rated ISO ( unless i have tested the film with my development and determined that another ISO gives better results ( I.E. 320 provides better negatives given my equipment and processing ) i would not change the ISO setting unless i could not get the f stop i needed for the shutter speed i require or vise versa, or the amount of light is not sufficient for recording an image. Bottom line, i would test that filter with that particular film to determine what the best ISO is for you. ( test with each film you would use that filter with.)

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The R72 has a filter factor of 16. Now a filter factor is a multiplier. We use this value by multiplying the exposure time without filter. Thus if the exposure time without filter is 1 second, then 1 x 16 = 16 seconds with the filter mounted. Alternately, the published ISO without filter is divided by the filter factor. If a film is rated at ISO 400 without filter, then 400 ÷ 16 = 25. A world of caution, while the math method described is accurate, the revised ISO for any filtered film is likely different and can only be determined by trial and error. Use this math method as a starting point.

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