how do you mount filters on unthreaded lenses?

[Brian Ellis]

Except with polarizers, you don't need to physically attach the filter to the lens with anything. If you did the Lee "snap-on" system that Darren mentions, which I used for quite a while, wouldn't work because that system doesn't hold the filter perfectly tight up against the glass and yet it works fine.

So just buy 4" square filters. Hold them by the corner with one hand in front of the lens, maybe just lightly brushing the outside metal rim of the lens or without even touching the lens, and trip the shutter with your other hand. Just don't push or shove the filter firmly up against the rim of the lens, if you do you might move the lens a little. Just get the filter up in front of the lens.

Works fine, I've been doing it for years ever since I looked one day at my Lee "snap-on" system and realized that it wasn't holding the filter tightly against the lens, there was a slight amount of space between the filter and the lens. So I figured I could do as well holding the filter by hand and dispensing with the rubber band and snap-on filter holder, which I've done. So I still use the Lee filters, just not with their holders.

[Sanjay Sen]

I use the Cokin P Series Universal Adapter Ring on those lenses that do not have filter threads.

(It becomes a problem on barrel lenses for which I use a piece of cardboard as the "shutter" as it won't block the light completely before I withdraw the dark slide.)

[Erich Hoeber]

I've added threads to my unthreaded lenses by glueing step-up adapter rings to the front of each with hot-melt glue. Very sturdy and easily reversible. I've standardized on 77mm filters. As others have mentioned, a Lee gel-snap and 4x4 filters are also a workable option, but personally, I found it to be a pain.

[David A. Goldfarb]

Clip on 3" square filter holder. Mine was made by Voss and has two barndoors--$15 used from KEH.

Lee Gel Snap for 4" square filters.

Tape.

For a couple of lenses, I've also epoxied a 3" filter holder to the back of the lensboard, though it's better in general to put filters in front.

Sinar filter holder on my Sinar.

Linhof compendium shade with 4" filter slot on my Linhof.

I've also used little spring clamps like pony clamps for doing things like clipping a 4" filter to a center filter with oversized front threads.

[jmcd]

I have one of the SK Grimes slip on filter mounts that accepts commonly sized screw-on filters, and I like it much. It is well made, and much in character with the lens.

[Gene McCluney]

I shoot fast, and a lot. I change lenses a lot...on my 5x7. I just hold the gel filter in front of the lens. Works for me.