In message ,
Alan Browne wrote:

Steve wrote:

I hope this isn't a silly question. Is it impossible or too expensive to
turn the sensor on and off or something instead of a mechanical shutter?
Just wondering.

In addition to the other replies I believe the camera manufacturers also
use the shutter as a black reference to measure sensor native noise.

For "noise reduction mode" for long exposures; yes. For normal
purposes, cameras may use blind pixel borders on the sensor. The 20D,
for example, has a vertical strip of 74 pixels wide on the left side of
the image, and a horizontal strip 12 tall on the top. The data from
these is where the JPEG engine and RAW converters get their black values
from (and they serve a s a noise sample as well). They are actually
contained in the RAW .cr2 file, and black is left with the offsets still
in them and in the exposed image (average is typically 128.2 to 128.4).

The Nikon D70 "electronically" shutter flash syncs up to 1/500 which is
on the "closing" side of the cycle, and I think that should be standard
on all high end DSLR's.

1/500 sync would be great; it would reduce the ambient softness when I
use flash fill with long focal lengths.
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John P Sheehy