Does any of the Illex lenses have filter threads, the few that I owned didn't? The only threads on any of mine have been where then element retaining ring was threaded in, what I do is buy on old rubber lens hood, strip the rubber off and use gaffers tape to secure the threaded portion to the front, so I can use standard filters...
I have the 161mm Ilex. Same for me - no threads. Buy a filter (or filters) that roughly fit the front of you rlens, and do like me, carry a small roll of black electrical tape to hold the filter in place.
Black electricians tape is almost as good as gaffers or duct tape, but smaller and lighter to carry when backpacking
Hi Allan, I double checked my Illex 190mm f4.8 acuton lens in a copal 1 shutter and it does not have any threads for using threaded filters. Also, I believe it may be a convertible lens. Yours maybe a convertible one too! Jon