A.S.
Member
I'm considering the 50/2.8 Elmar-M as my compact summer daily, but would prefer more than a 6 blade diaphragm. Is it possible to replace its diaphragm with that of a donor lens'? If so, what sort of specs would that lens need to have?
Swapping Diaphragms
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rfaspen
[insert pithy phrase here]
Very unlikely. An email to Don at DAG Camera Repair will provide the definitive answer.
Phil_F_NM
Camera hacker
No.
And yes.
The Leica 50mm lens is a nominal focal length of 51.6mm across all the designs with the exception of the DR Summicron which is 51.9mm. That is in your favor. That said, the lens is designed to put the nodal point 51.6mm from the focal plane but has nothing to do with the physical size of the lens from one design to the next. For example, an SMC Takumar 50mm f/1.4 has a nominal focal length of 51.6mm as well. But it is a retrofocal lens AND it is huge in comparison to the Elmar. The aperture's physical opening in relation to the lens' size is going to be different from the f/stop. Although the lens is a 50mm, at f/2 this doesn't necessarily mean the aperture is 25mm across. It is a representational number that is more arbitrary when actually measuring physical dimensions.
So to simply find a donor lens with 7 good aperture blades isn't enough. You have to know the physical dimensions and match T stops between your lenses to get the same performance.
All that said, you could do it with enough money.
Phil Forrest
And yes.
The Leica 50mm lens is a nominal focal length of 51.6mm across all the designs with the exception of the DR Summicron which is 51.9mm. That is in your favor. That said, the lens is designed to put the nodal point 51.6mm from the focal plane but has nothing to do with the physical size of the lens from one design to the next. For example, an SMC Takumar 50mm f/1.4 has a nominal focal length of 51.6mm as well. But it is a retrofocal lens AND it is huge in comparison to the Elmar. The aperture's physical opening in relation to the lens' size is going to be different from the f/stop. Although the lens is a 50mm, at f/2 this doesn't necessarily mean the aperture is 25mm across. It is a representational number that is more arbitrary when actually measuring physical dimensions.
So to simply find a donor lens with 7 good aperture blades isn't enough. You have to know the physical dimensions and match T stops between your lenses to get the same performance.
All that said, you could do it with enough money.
Phil Forrest
A.S.
Member
Don would certainly be the final step in this realization.
Thanks, Phil, for the insight. Perhaps the original f/2.8 Elmar blades would be an option, but not the 10 blade diaphragms of the Voigtlanders that I already have available to me.
Thanks, Phil, for the insight. Perhaps the original f/2.8 Elmar blades would be an option, but not the 10 blade diaphragms of the Voigtlanders that I already have available to me.
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