[MacDV] Digital SLRs

[Danny Grizzle]

On 1/1/03 1:38 PM, "Richard Brown" <richard at go2rba.com> wrote:

> With
> the digital cameras like the S1, you do not want to change lenses
> too often, as it is simply way too easy to get dust related artifacts
> on the CCD, which are only visible when viewed on a computer
> screen, which in turn means you do spend some time cleaning
> the CCD as a preventive measure in the field, else suffer more
> (unnecessary) work in Photoshop. This dust related problem
> happens even when you're CAREFUL.

Olympus E-10 & E-20 literature makes a big deal about the advantage of a
fixed lens in digital photography, and claims that conventional CCD elements
present a honeycomb surface which tends to catch & hold microscopic dust
particles. Cleaning the CCD in digital SLR cameras is a major, major issue.

I'm curious exactly how the Sigma SD9 dust barrier works. Would it be
possible to put the CCD in a sealed compartment, with an optically clear
barrier well forward of the CCD, so as to throw any dust present completely
out of focus?

In the late 60's, Canon used to make a SLR camera called the Pellix which
used a fixed semi-silvered surface in place of an instant return mirror.
This "pellical mirror" passed light both to the viewfinder and to the film
simultaneously. Later, they incorporated a refined version of this concept
into a special purpose pro SLR, a Canon F1 modified with a non-removable
high speed motor drive (something like 9 fps).

Many motion picture cameras have contained similar optical blocks, to allow
simultaneous SLR viewing and film exposure. The potential tradeoffs would
appear to be image quality, lower viewfinder brightness, and less light
available for exposure.

At any rate, it would appear that an optical assembly could be sealed to
prevent dust at the image plane, the point of focus. Or is the optical block
in HiDef video cameras an impediment to image quality?

BTW - the conclusion of the dpreview.com review for the the Sigma SD9
faulted the camera for sloppy quality control, with dust present on the CCD
of a brand new camera.

Danny Grizzle