On Mon, 30 Sep 2002 10:49:58 -0600, "John Sparks" wrote:
>"Neuman - Ruether" wrote in message
>news:3d9a9684.14200959@newsstand.cit.cornell.edu

>> But the 21mm Nikkor f4 non-retrofocus had far more
>> flare-tendency and illumination corner roll-off than
>> the sharper retrofocus 20mm f2.8 Nikkor does... It
>> does not surprise me that a "somewhat retrofocus"
>> design could have the best mix of design compromises,
>> since both design types (retro/non-retro) offer
>> advantages/disadvantages...

>A retrofocus wide angle lens always has less illumintation falloff than a
>non-retrofocus lens. The light rays exit the lens more perpendicular to the
>film. For the same reason, a retrofocus wide angle also projects circular
>objects near the corners of the image closer to a circle than a
>non-retrofocus lens. With current technology for coating, designing and
>manufacturing lenses, I doubt there are any real advantages of a
>non-retrofocus lens anymore.

I mostly agree with the first (some retrofocus WA designs,
though, show about as much illumination roll-off as some
non-retrofocus designs...), disagree with the second
(assuming equal format, angle of view, linear distortion
and flat film - a rectangular projection is a rectangular
projection, regardless of method used, all else being
equal...), and partially agree with the third (it is still harder
to design for low linear distortion with flat field with
retrofocus designs, and VERY few retrofocus designs
show really low linear distortion...).