Jeff Keller wrote:
> Bringing back an old subject ...
>
> This is the first time I've seen a ray diagram that sort of shows why
> the camera body might need to have a larger lens mount for a
> telecentric lens for a __particular sensor size__.
>
> However since the sensor is smaller than a 35mm frame it doesn't
> really imply that the four-thirds mount has to be as large as a 35mm
> lens, The rearmost lens element is still smaller than the sensor.
>
> <http://www.four-thirds.org/en/about/benefit.html>
>
So you are an engineer charged with designing a lens mount for not yet
extant lenses that are to be telecentric for a certain sensor size.
Maybe there are some lenses in the design stages, but you are designing
a new standard that will, with luck, support many future lenses, many
not designed by Oly. So you really know nothing except sensor size and
telecentric lenses coming along.
So what can you do but assume that, worst case, you need room for a lens
element with a clear diameter equal to the diagonal of the sensor, held
just clear of the movement arc of the mirror. So you take that diameter,
add for supporting structure, focus helicoid, etc. then add a little for
safety.
If you are any sort of thoughtful student of historical camera design,
you will be aware of the many advantages Canyon got with the extra large
diameter of the EF mount and will be generous with the "safety margin".
Also, the illustration you linked to is not of a fully telecentric lens.
The edge rays aren't perpendicular to the sensor plane. So the words and
the illustration are not in agreement. Think either existed in that form
when the lens mount was being designed?
Moose
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