Use two threaded circular filters at once and you run a terrible risk: they might get stuck together. It happened to me when I was using a neutral density filter and a circular polarizer. Here’s how I got them unstuck.
A quick bit of research on how to unstick two filters turned up a few techniques that didn’t help. If your filters aren’t stuck too badly, they might work for you, but they didn’t for me. I tried:
- Just twisting the filters really hard. They didn’t budge at all.
- Using kitchen gloves for better grip. Again, the filters didn’t move.
- Tapping around the edge with your finger or a knife handle. I’m not sure how this is supposed to work, but it didn’t.
Thankfully, I found one solution that worked an absolute treat. I took my two filters and popped them in the freezer for 15 minutes.
When I took them out, the two filters detached easily. The metal obviously contracted a tiny amount in the sub-zero temperatures, which let them spin freely. The filters were totally unharmed; the only thing to show they’d just come out of the freezer was a small amount of frost on the glass.
If you’re in a similar situation, just stick your filters on ice for a few minutes. It should do the job.
The Nuclear Option
And, if it doesn’t work, there’s always the nuclear option: sacrificing a filter.
Decide which filter is less valuable (either because it’s scratched and scuffed, or just cheaper to replace), and very, very carefully, break it with a chisel, glass breaker, or other similar object. Without the glass in the filter, you’ll be able to use pliers to get a proper grip on the metal ring and unscrew it from your unbroken filter.
Have you unstuck two filters that were stuck together? Let me know what worked for you. I’m sure I’ll need to do it again.