Step ring for 40.5 to 39mm?

[scottgee1]

My RF kit is, by design, based on 39mm filters. I'm considering adding a 40/2.0 Rokkor which uses 40.5.

Would a good, i.e., thin step ring cause noticeable vignetting? Not much I'm thinking as the difference is on 1.5mm which means .75mm all around.

Or am I missing something . . . ? 😕

TIA!/ScottGee1

 

[richard_l]

When I got my 40mm Rokkor, I looked for such a step-down ring but was not able to find one. It will either vignette (cut off the corners) or not vignette. I think it would probably not vignette, since 39mm filters can be used on the 40mm Summicron-C without vignetting. Anyhow, I ended up buying a few 40.5mm filters for my Rokkor. I figured that such a fine lens deserved its own filters. 🙂

I wonder whether it might be possible to wrap the threads on a 39mm filter with teflon tape so that it can be screwed into the Rokkor. I've been too lazy to try that.

Richard