To Filter, or Not to Filter (CV 12mm f/5.6)

[phutro]

Hullo all! Just made the leap to an RF system (Bessa R4A) and had a question about the 12mm. I know it vingettes, but would placing a UV filter on it (protection purposes) cause even more? Anyone have any idea / examples?

Regards,

 

[stompyq]

which version of the 12mm?

 

[phutro]

The new m-mount.

 

[Tom A]

You need the 67mm filter and if would not add to the vignetting. It is a 12 mm lens and it has edge fall off - though far less than one expects. If you want to correct for it -you need a filter with a graduated center spot to compensate (probably cost almost as much as the lens!!!!). I have tried it and found it useless. The edge darkening is remarkably modest for a lens with a 127 degree coverage!
If you scan your images - there are programs that can assist in minimizing vignetting - though I have never bothered to use them. The view of a 12 is dramatic enough that the slight vignetting actually helps "centering" the image.

 

[phutro]

Thank you!

 

[bigeye]

Ultra-wides suffer from natural vignetting or fall off from the radical bending of light - can't get away from it, except with a 'center filter' which has a graduated ND spot in its center to balance light values with the darker corners.

Mechanical vignetting is the obstruction of coverage by a filter or hood, a bit different.

The ever handy Ken Rockwell covers it here (scroll down). I agree with him too, I don't bother with it.

- Charlie