Efke/MACO IR820 exposure index

Does anyone have some experience to share regarding how to expose this film with a deep red filter? I'm planning to use a Hoya R72 filter, and meter before installing the filter. I'm estimating that I should be using an effective film speed of about 6 -12 ISO. Will be daylight exposure, 35mm. As it will be my first experience (experiment?) with this film, I do plan to bracket +/- 2 stops.
Development plan is Rodinal 1:25, 8-9 minutes. Advice???

Bracket and take notes.

I use an 89B and rate it at either 1.5 or 3

My first attempt of ISO 3 through a 720 nm filter (such as the R72) was underexposed. 1.5 - 3 will be a safer bet than 6-12.

I'd take a few reads through the data sheet for this film, and go out and try some test rolls. You can get to it from the Freestyle Website.

The main thing is that how to expose it depends on the amount of IR present in the composition.

The filter factor for the R72 is 32x, requiring opening five stops. IMO, this only works on a bright clear day with a speed-enhancing developer. I consider the film to be a 25 or 50 film with a normal developer like HC-110 or D-76, and then I apply the filter factor.

Unfortunately, bracketing with this film proves to be expensive. Shooting 6x7 is just as expensive per shot as shooting a regular black and white film in 4x5 size (about a buck a shot). As such, I would try it out in 35mm for testing before spending the bucks on the larger formats.

More like 3 ISO and as said above, Bracket. 2F/2F's statment of useing a speed enhancing developer is a good one. I am useing Diafine for this film.

I hope you don't run into (there was a url link here which no longer exists)

Jason

I rated it at 1/2. Keep in mind that bracketing to the thin side may not be satisfying. Film rarely improves with under exposure.

I've had pretty good luck with the EI 6-12 range in evening light, when the amount of IR relative to visible light is high, but for midday it's probably a couple of stops too optimistic.

Diafine does work nicely with this film, although I'm not sure if I get a speed increase---I use it more for highlight compensation, because it seems to keep the highlights from fusing into a big mass of white and so makes the Wood effect less visually outrageous.

-NT

Travis Nunn said:

Bracket and take notes.

I use an 89B and rate it at either 1.5 or 3

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that's what I do too. what he said is a good start but you've got a different filter.
During mid day 4 sec@22 works for me as a starting point. Don't forget reciprocity if you get into longer exposures with this stuff, not that you will with 35mm.