I have a question for any owners of the PL 42.5: Have any of you used a 67-58mm step down ring on your lens, with no vignetting wide open? I'm thinking of possibly picking up a Nocticron, but I'd like to be able to use all of the 58mm filters I have with it (two CPL's, a 3 stop ND, a 10 stop ND, two variable ND's). I'd be curious to know if a 58mm step down ring can be used without causing vignetting. If no one has tried this, could you measure the diameter of the front element? I'm curious to see just how much land there is between the edge of the front element, and the filter ring. From the best I can tell, it appears that there is at least 5mm of space between the edge of the element and the filter threads, so it should be able to accept a 58mm step down ring, but I'd like to have somebody actually measure the element to confirm my thoughts. Thank you in advance for your help!
The only scale I have is in inches but this amateur measures an outer edge of lens barrel to other outer edge is 2 11/16" with the edge of glass front element diameter is 1 3/4". I hope this helps. Bobby
@zensu, thanks for your help. 1.75 inches puts it at 45mm, well below 58mm. And I realized that the Nokton 42.5 f/0.95 uses a 58mm filter thread, so if an f/0.95 lens can use 58mm filters, then I should be able to use 58mm filters no problem on an f/1.2 lens, which is more than 2/3 a stop slower.
Unfortunately it's not that simple. The Nocticron has larger lens elements than the Nokton, due to being designed for higher performance and most notably higher cross-frame performance at wide apertures. You can't make the assumption that because a faster lens has a smaller filter ring, that you can therefore use a step-down ring. Very different lens designs here.
Lenstip has the Nocticron's front element size at 45mm. My best guess/measurement puts the "ridged" portion just outside of the front element at a diameter of about 58mm, so the step-down ring should be usable without any added vignetting.
