At 11:33 PM +0000 6/11/03, olympus-digest wrote:
>Date: Wed, 11 Jun 2003 14:11:42 -0700
>From: Jan Steinman <Jan@xxxxxxxxxxxxxx>
>Subject: [OM] Re: 4/3rds, 16Megapixels?
>
> >From: Albert <olympus@xxxxxxxxxxx>
> >
> >Sony just coughed up 8 megapixel CCD's in a 2/3's " configuration. If
> >that is translated to 4/3rds which I think is suppose to be 2x the
> >surface area, then that's a 16 megapixel possibility?
>
>Possibly, but at what cost?
>
>Semiconductor yield goes down and cost goes up with the square (or even cube)
>of area.
The scaling law is the Poisson distribution: Flaws are randomly distributed.
Even one flaw kills the chip. Double the area of the chip, double the average
number of flaws in the chip. If the average number of flaws per chip is low
enough, then most chips will by luck be flawless. As the average rises, then
more and more chips are unlucky. What saves us is that many chips have more
than one flaw, allowing others to have no flaws. I suspect that for image
sensors, which are quite large, the average yield (fraction of the chips on a
wafer that are good) is low, perhaps 25 0f memory serves. The cost per wafer
is more or less fixed, so the cost per chip basically depends on the yield, and
one of the most closely guarded business secrets is the actual yield.
In this regime (~25% yield), changes in chip size have large effects on yield,
but the real law isn't so simple as the square or the cube.
>So if there is such a beast, expect it to cost 4-8 times as much.
>
>That's why you don't see any full-frame 35mm digitals fur under four grand or
>so -- the body and other electronics on the 10D and 1D are pretty much the
>same, yet the full-frame one costs 6x!
More or less true, although handling more pixels makes the body electronics
more expensive, because more storage is needed to hold a reasonable number of
images, and the speed of the electronics must increase (so image capture and
storage times remain reasonable).
Joe Gwinn
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