How do I prevent light leaks and reflections when using ND filters for long exposures?
Asked 2/28/2019
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2 answers
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When I shoot long exposures with an ND filter in a holder, I sometimes get visible reflections or flare in the image. It seems like stray light may be entering through the gap between the lens and the filter/holder. Is there a good way to reduce or prevent this?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
4
For starters you could put the filter in the closest slot, to close the gap a bit.
If it's still noticeable, I'd try some black electrical tape over the gap.
Remember to take it off again before you put it away for any length of time. It's the kind of tape that's easy on/off to start with, but gets horribly slimy if you forget it for 6 months.
Potentially it could simply be light coming through the filter, rather than from the edges, so you still may not eliminate it entirely.
If it is coming through the filter itself, you could experiment using each of the 3 slots on the filter holder & see which gives the least noticeable result.
...and xiota's idea of a lens hood could work if the light causing the interference is coming from out of frame. I've never tried putting a hood over a Cokin, but perhaps someone does a matte box that may fit in one of the slots??
Ouch - if you have the money - Cokin Matte Box, Model Z360 with an Integrated Z-Pro Filter Holder
Originally by user57929. Source · Licensed CC BY-SA 4.0
user57929
7y ago
0
Generated from our catalog & community — verify before relying on it.
Yes. This is usually caused by stray light leaking into the filter holder and reflecting off the back of the filter.
Try these fixes:
- Put the ND filter in the rear/closest slot of the holder. This minimizes the gap between lens and filter and often reduces the problem a lot.
- Check whether your filter holder has a light-blocking gasket or sealing accessory. Some systems include gaskets that cover the gaps around the filter.
- If needed, block the gap with a temporary cover such as black electrical tape or even a soft lens bag/dark cloth over the holder. Don’t leave tape on long term, since adhesive can get messy.
- Test different slots if your holder has several; sometimes one position shows less reflection than another.
- If strong off-axis light is hitting the front of the filter, a hood or makeshift flag can help, but from the symptoms described the main issue is likely light entering from behind the filter, not through the front.
In short: use the rear slot first, then add sealing/covering if needed.
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UniqueBot
AI7y ago
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