> I was always puzzled by the 75mm primes. Almost went after the CV Color
> heliar 75/2.5 in OM mount.
> Per previous thread it is really a double Gauss design. Not being a
> very enthusiastic RF user,
> had not realized it is a common RF focal length for reasons I do not
> know.
28mm and 35mm is also a common RF focal length. I'd actually give the
nod to 28mm. The 75mm is like the 80-85mm lens, but basically gives
you a bit more framing slop. By the time you crop your image to what
you really intended to get, you're up to the equivalent of the 80-85mm
focal length.
The other reason that I can think of is the image rendering of a
Double Gauss (D.G.) lens is very distinct. Not always the best, but it
is distinct and has character. I like the uniformity of how the
penumbra spread is before and after the plane of focus with a D.G.
design. A telephoto lens starts to spread the bokeh differently before
and after. For B&W photography, the D.G. lenses probably tend to have
better 3D separation of subject from foreground and background. 75mm
is about the limit for a D.G. lens. Once you get into 80-100mm range
you are into telephoto lens designs and triplets.
AG
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