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Focal reducers for crop sensor DSLRs
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PostPosted: Tue Nov 11, 2014 2:35 pm    Post subject: Focal reducers for crop sensor DSLRs Reply with quote
Is there any reason why a focal reducer can not be made for crop sensor Canon, Nikon etc DSLR cameras?

I expect the mirror could be an issue with a normal one, but you can get lensed adapters for most body/lens combinations eg MD/Nikon, FD/EOS etc, could these be combined to make a good reducer?

In theory?


PostPosted: Tue Nov 11, 2014 2:59 pm    Post subject: Reply with quote
As far as I know, any FL shortens the register distance considerably (that's why an FL-adapter is always shorter than the corresponding normal one). And shorter register distances don't go along well with mirror boxes.


PostPosted: Wed Nov 12, 2014 1:42 am    Post subject: Reply with quote
I surmised this and thats why I mentioned the extra element similar to the ones in FD/EOS for example.


PostPosted: Wed Nov 12, 2014 7:06 am    Post subject: Reply with quote
I think it could even be possible to make a EF-EF-S reducer. And reducer for M42, Contax/Yashica and other lenses with longer register distances. For FD to EF-S camera I don´t know, that would need probably a new optics design concept.

For the EF lens to EF-S body one would need a Bravais lens system, which allows magnification change without altering the position of the lens and sensor. This special adapter has to fit inside the free space between camera mirror and back lens - and should have no EF mount - no tube, no change of distance between sensor and lens.
This space constraint could be a big problem. Furthermore is could be impossible to construct one adapter working with all EF compatible lenses.

A bit information about Bravais lens systems:
http://www.globalspec.com/reference/73838/203279/2-6-bravais-system


PostPosted: Wed Nov 12, 2014 10:11 am    Post subject: Reply with quote
ZoneV wrote:
I think it could even be possible to make a EF-EF-S reducer. And reducer for M42, Contax/Yashica and other lenses with longer register distances. For FD to EF-S camera I don´t know, that would need probably a new optics design concept.

For the EF lens to EF-S body one would need a Bravais lens system, which allows magnification change without altering the position of the lens and sensor. This special adapter has to fit inside the free space between camera mirror and back lens - and should have no EF mount - no tube, no change of distance between sensor and lens.
This space constraint could be a big problem. Furthermore is could be impossible to construct one adapter working with all EF compatible lenses.

A bit information about Bravais lens systems:
http://www.globalspec.com/reference/73838/203279/2-6-bravais-system


Difficult, but not impossible if a 'new optics design concept' were implemented.


PostPosted: Wed Nov 12, 2014 10:29 am    Post subject: Reply with quote
philslizzy wrote:
I surmised this and thats why I mentioned the extra element similar to the ones in FD/EOS for example.



The question then is if such an extra element would deteriorate the quality too much.


PostPosted: Wed Nov 12, 2014 10:40 am    Post subject: Reply with quote
LucisPictor wrote:
..
The question then is if such an extra element would deteriorate the quality too much.


Due to the image reducing it could be possible without the lower image quality we know from those image enlarging teleconverters in normal FD-EF mount adapters. Most of these FD-EF adapters with ~1.26x teleconverter seem to have very cheap lens-systems inside.
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