guy_brooker

My reply is a bit 'after the event' but it relates to some observations just recently made with my own S2A system.

My lenses focus correctly at the infinity stop but 'sharpest focus' does not coincide with helicoid distance scales at closer settings.

My S2A came originally with the 80mm Zenzanon f2.4 and helicoid distance scales for(I think) 75mm and 80mm lenses. After buying a 50mm Nikkor, I bought a helicoid marked for 50, 75, 135 & 200mm lenses but decided to swap the distance scales only because the eBay acquired helicoid had some other mechanical issues. Now I notice the considerable lack of agreement with sharpest focus and distance marking on the 135 and 200mm lenses I've just bought.

I wonder, do Bronica helicoids differ in the pitch of their threads? I can't think of any other explanation since this is s problem of 'scaling' and not 'offset'. The latter being explained by the position of the ground glass focusing screen.

The Bronica lens hood is a bayonet fit on the forward-most part of the lens, not on any supplementary filter, so no problem in this direction.

Guy Brooker