I have a confession to make: I destroyed my first Triple Bandpass TB550/660/850 filter (great for Aerochrome experiments) trying to get the glass out of the filter ring. Yes, that’s how it goes sometimes when you try things (and are a bit mindless and overambitious like me). But that is in the past. I was able to buy a new one, a little smaller, but that’s even better.
My intention then and this time was to take the glass out of the ring to put it behind the lens. With the ring, the whole thing protrudes too far, so the mirror hits the glass – and you want to prevent that.
So how does that work, disassemble a filter? Actually, it’s very simple: Get some protection for the glass that you can put between the ring structure and the glass – this can be a round piece of cardboard or a small cloth. Then take something with which you can unscrew the glass holder. Actually all glass filters have a relatively simple construction, so you can unscrew a ring to get the glass free.
I used a pair of scissors. Put the two blades into the small recesses in the filter ring (look at the small gap in the ring in the picture). Put them there, then turn them counterclockwise (with the scissors tightened) until the ring is wrung out.
After that you have a round piece of glass that you can stick behind the lens. Of course, this does not work with all lenses, but with most.
The big advantage of this technique is that you don’t have to buy filters with large diameters (which in this case would have cost me several hundred francs). And in this way, the filter is also better protected.