In article <4tqo71$fkc@nntp4.u.washington.edu>, zeming@u.washington.edu says...

> I notice more and more modern lenses sacrifice
>field curveture for other features (wider
>zoom range, higher sharpness..). How important
>is the field curveture for normal photography?
>I'm sure it'll be very noticeable in macro
>or copy photography, but in a more common
>situation, say a head&shoulder portrait or even
>weaker, a group portrait at a 10ft
>distance and f/5.6-8, will it be a issue
>at all? My concern is, with a lens of high
>field curveture, areas away from certer don't
>even focus on the film plane, therefore making a
>larger dot in the image (softened). What's
>the point of sacrificing field curveture to
>get higher resolution then?

What an interesting question! This is an often
overlooked area (I suspect due to the fact that
most high-quality lenses don't have noticeable
field-curvature, and the poor lenses that do
are used by people who don't care (or who don't
notice it), or shoot primarily photos that don't
show it. In Nikkor lenses, among the rather large
number of them that I have used, only a few have
shown it: some samples of the 55mm f3.5
Micro-Nikkor (!!), the 135mm f2 MF (very slight
amount, just enough noticeable at infinity focus
to spoil the otherwise exceptionally sharp lens
for aerial-photography use at wide apertures),
and the 28-50mm f3.5 zoom (rather noticeable
field curvature, but a very sharp lens over the
whole field otherwise). All samples of the
Zeiss Planar 75mm f3.5 (!!, also!) on the Rollei
twin-lens also showed considerable field-curvature
that made most photography at apertures wider than
f11 difficult (the lens is sharp over the whole
field even wide-open, but just not in the same
plane). If you never shoot a horizon, a large
group photo, flat copy work, distant scenes
at wider apertures, or other relatively flat
subjects, you may not be bothered by it - but
it does limit what kind of photos you can take
at wide apertures, not something I willingly
accept.
Hope This Helps