Originally Posted by europanorama
Need to know which lens-50 or 75mm is nearest to the film-plane.
The nodal point of the 50 obviously is 25mm closer...
If you want to know the rear element distance, the 50mm has the very short rear lens to film plane distance characteristic for Biogon type lenses - I'll measure that on occasion.
Never had a 75mm - but if the Internet is right, it is another Biogon type so that its distance will be a bit bigger (probably less than the 50:75 ratio - you'd have to get the image circles into the calculation as well). Besides, from pictures (where the outer surfaces look flat rather than strongly curved) I do suspect that the common belief that it is a Biogon clone might be way off the mark - it looks more like a generic (Super Angulon type) large format wide (Zeiss also made a few large format wides of similar type, which they marketed as Biogon, causing some confusion between Biogon brand and Biogon type), whose geometry would be very different.
As far as the mount distance is concerned: How do you propose to measure it, given that it has no proper flange? Breech lock mounts generally need some calibration block inserted in place of a lens to create a artificial reference point for measurements - and I am not aware of anybody (presumably apart from Mamiya service) owning such a thing.