Red Filter Factors

[Sirius Glass]

I am working on figuring out the filter factors for black & white film and black & white IR film without wasting the two rolls of HIE film and some rolls of Rollei IR 400 film.

By the way, how do I get rid of "Download from the table?"

Filter Number	Filter Factor
23A	2 2/3
25	3
29	4
72	?

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[Andrew O'Neill]

For the 72, I give 5 stops more exposure when using Rollie IR. How old is the HIE? I've got some sheet film from the late 60's. EI 12 for the #25. No clue how to get rid of the download from the table...

 

[Sirius Glass]

So start with

Filter Number	Filter Factor
23A	2 2/3
25	3
29	4
72	5

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[Svenedin]

For Rollei IR I use 4 stops more exposure with an R72. This has worked consistently well for me but I’m aware than many people use 5 stops. I think this may have something to do with differing developing times for this film. The dev times from massive dev chart are very different to those printed on the inside of the Rollei IR box (or at least they are on the boxes I have). The reason I arrived at the +4stop filter compensation is that my Olympus OM4-Ti can meter through the filter (with the EI set at 400) and the photos turned out well. By taking the filter off I could tell the camera was adding 4 stops. I used this on my rangefinder 120 cameras (which can't meter through the lens) and those photos worked out well too. For safety's sake I would suggest bracketing with +4 and +5 stops. Remember to take at least one picture on the roll without a filter at EI 400 which is a check of proper development. I've never used HIE so can be of no help with that.

 

[David A. Goldfarb]

No idea why it says "download," and I can't get rid of it, but it doesn't seem to be hurting anything. If someone wants to download the red filter factor table, they could paste it into their field notebook or put it into their filter wallet.

 

[MattKing]

If you click on the "Download", the browser will download to your computer the table in Excel format.

 

[Sirius Glass]

If you click on the "Download", the browser will download to your computer the table in Excel format.

Ok, that explains it. Thank you. Have not slept for nights worrying about that.

 

[Sirius Glass]

So what I have gathered is that filter factors for the R72 filter when using HIE, Iflord SFX and Rollei IR 400 films is: