Panasonic 7-14 Filter Revisited

A lens that can't use filters is missing out on a lot, especially with polarizer and ND filters. When I bought my 7-14 it was with the intention of coming up with some sort of filter holder. After reading about some solutions I decided to try my own instead of copying others. One design goal was to be able to use the filter at 7 mm without vignetting (in retrospect close to impossible or at least extremely difficult).

Looking at the lens it appeared that in order to minimize vignetting the filter must be kept as close to the front element as possible, maybe 2 mm away for some margin of safety. Since the front element moves while zooming the filter holder would have to reference from the moving portion of the lens.

The front element never extends past the shorter (horizontal) portions of the built-in hood so I used that dimension to start with. About 10 mm spacing is sufficient to keep the filter from ever touching the lens element. An outer diameter of 65 mm fits nicely into the hood, the inner diameter should be as large as possible while still providing sufficient strength (and capability of being machined). About 1.5 to 2 mm thickness looked like it would work and should be machinable in plastic or metal.

I found a piece of 64.5 mm plastic tubing with a 2 mm thickness so it required little machining. Other options are a 2.5" plastic pipe fitting or 2.5" OD metal tubing. Once the OD and ID were right I trimmed the piece to 10 mm thick. A lathe was used for making the part, this should be something that any shop can make for not too much $$$. Some of the online shops should be good at this, I can provide a drawing on request.

The polarizer/ND glass should be as close to 65 mm as possible too. A Hoya 67 mm Super CIR-PL polarizer is the perfect diameter! This is an older filter, hopefully they are still the same size. The filter came out of the ring easily, just unscrew a retainer ring.

The filter needs to be attached to the spacer, I thought of silicone adhesive but plain old Scotch tape around the edge seems to work ok. I also used some tape to get a snug fit for the spacer inside the lens hood. It won't fall out but can still be rotated although it is best to orient the polarizer before inserting it into the lens.

Vignetting does not occur before 8 mm and even at 7 mm it is not bad, just a bit in the corners. I consider the project a success!

The parts.

The completed filter, it works better than it looks.