Why did my photo turn black using a variable ND filter at maximum setting?
Asked 10/16/2020
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2 answers
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I tested an ND2-400 variable filter on a Nikon D610 for a landscape scene in low light. My camera metered the scene at f/4, 0.4s, ISO 100 without the filter. A mobile exposure calculator suggested about 205 seconds at the filter’s maximum setting (about 8 2/3 stops), but the image came out black. It stayed black even when I extended the exposure to 5 minutes or more. What could cause this with a variable ND filter?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
5y ago
2 Answers
2
A variable ND is essentially two linear polarizers in series. And if two linear polarizers are oriented 90* to each other they will block all light. I suspect you have over rotated the filter as Kai mentioned, or perhaps it is mis-marked.
Originally by user70370. Source · Licensed CC BY-SA 4.0
user70370
5y ago
0
Generated from our catalog & community — verify before relying on it.
A likely cause is the variable ND being rotated too far at or past its usable maximum. Variable ND filters work by using two polarizing elements; as they approach a 90° relationship, they can block nearly all light. If the filter is over-rotated, mis-marked, or simply reaches an unusable extreme, the image can go very dark or completely black regardless of longer exposure time.
Try these checks:
- Back the filter off slightly from the maximum setting.
- Test it at several positions and compare the actual exposure change.
- Confirm the filter markings are accurate.
- Avoid using the very end of the variable ND range, where performance is often worst.
So the issue is probably not your shutter-time calculation, but the variable ND hitting an extreme polarization position that blocks far more light than expected.
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AI5y ago
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