<aniramca@[EMAIL PROTECTED]
> wrote in message
news:5b818771-9c68-48b0-8b3a-cb3f61760252@[EMAIL PROTECTED]
>I read some info about the 51 point AF system for the new Nikon D300.
> The dpreview showed a graphical presentation on the locations of those
> 51 points within the targeted digital frame (approximately covers 2/3
> of the square, centered in the middle of the frame). Could someone
> provide a little more detail about this 51 point system?. I may be a
> little confused about this concept against the exposure metering in
> some old digital cameras.... averaging or spot metering. I guess that
> this is not about the light exposures, but instead it is about the
> distance measurements from the object(s) to the sensor plate. If the
> later is correct, then how do they manage to get a razor sharp picture
> if you have to average the distances over 51 spot locations? Or, did
> the camera actually take average distances from those 51 locations? I
> guess you cannot have 51 different focused distances to the sensor and
> each measured distance will be registered into a single 2D plate, can
> you? Or, I may miss something completely and more fundamental here? I
> think that taking average distances over 51 points will not definitely
> work to produce a razor sharp image on the main focus/target area,
> unless each of those 51 points have identical distances (or close to
> identical distances) to the sensor.
> Thanks for discussion and comments.
More likely that the uP reads the various distances, decides which are
the near ones (and thus likely the subject(s)) and adjusts the focus
point for those, possibly adjusting exposure by aperature at the same
time to ensure sufficient depth of field to cover them all.
--
Woody
harrogate three at ntlworld dot com
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