How should I meter a Bronica ETRS with a 10-stop ND filter on film?
Asked 6/15/2019
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I’m using a Zenza Bronica ETRS with the AE-II prism finder meter. Without the filter, a scene meters at 1/60 sec at f/8. After fitting a 10-stop ND filter, the TTL meter suggests much shorter exposures than expected—often around 4 seconds instead of about 16 seconds, and sometimes only 7–9 stops more rather than the full 10.
For film, especially slide film, should I trust the TTL reading with the filter attached, or meter without the filter and then add the filter factor?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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With my long exposures, I meter for the scene and then add whatever ND amount needed and disregard the camera’s meter from there on out. That being said, it wouldn’t hurt to do some testing to determine more about your particular filter’s characteristics (I’d recommend using a digital camera for the testing). Take a regular exposure, manually adjust 10 stops and shoot, then go 8 and 9, 11 and 12, and see which is the most accurate LE.
At those slow of speeds, don’t forget to adjust for reciprocity failure.
Originally by user67377. Source · Licensed CC BY-SA 4.0
user67377
7y ago
0
Generated from our catalog & community — verify before relying on it.
Meter the scene without the filter, then add the filter factor manually, and after that correct for reciprocity failure.
A 10-stop ND should theoretically turn 1/60 sec into about 16 seconds at the same aperture. However, film is not linear at long exposures, so once you get into multi-second times, reciprocity failure becomes important. That means the final exposure usually needs to be adjusted based on the specific film stock’s data sheet.
So the practical workflow is:
- Meter the scene without the ND filter.
- Add the filter’s rated density (about 10 stops, if accurate).
- Apply the film manufacturer’s reciprocity correction for that exposure time.
It’s also worth testing your particular filter, since real-world density can vary slightly. A simple bracketed test can show whether your filter behaves closer to 9, 10, or another value in practice.
For slide film especially, testing and using the film’s published long-exposure guidance is important.
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