Digital BW, The Print

Steve,

 
> There is a discussion here about the optimal pixel size under digital
> image sensors:
> 
> http://www.normankoren.com/Tutorials/MTF7.html
> 

Yes, that site has a lot of good information.  However, I was wondering more
about what fundamental limits might exist on the technology.

I suspect that companies like Canon have looked at fundamental limits in
making their long term plans.  So, aside from the factors that affect one's
choice given today's technology, it would be interesting to see an analysis
of where a practical end point of sensor shrinkage is. 

Canon fabricates its own semiconductors, I believe.  As such they probably
are, in at least the fab division, up to their eyeballs in these problems.
I don't think any other camera manufacturer has a fab.

The diffraction limit of light is one obvious problem.  The semiconductor
industry has fought this battle for years, but they have been able to avoid
the limits imposed by the wave length of visible light by going to UV light
and even non-glass optics.  The camera manufacturers will not have these
options.  So, I'd guess this imposes a practical limit on how small a sensor
of a given resolution can be.

There is also what I think is referred to as "shot noise."  The particle
nature of light causes, among other things, the sensors to detect not a
smooth ramp of increasing exposure, but the steps caused by the quantum of
each photon hitting the sensor. The quantum nature of light appears to
result in significant problems, including noise, as the cell size decreases.
This in combination with optical diffraction, will probably put a lower
limit on the cell size.  Of course, it may be so small that it will have no
impact on any living photographer.

Probably a more practical current factor will simply be the economics of
making a full system of lenses and accessories for any particular sensor
size.  This will probably cause there to be discrete plateaus.  I would
guess Sigma and Tamron will follow Canon.  If they see Canon making specific
lenses for a sensor size, they may assume it will be a significant enough
standard to invest in making third party lenses.  Then again, Canon might
predatorily sucker the third party manufacturers into wasting lots of
development money on what turns out to be a very fleeting, "false" standard.
It would be fun to be a fly on the wall of the decision making bodies here.
I sense there is a lot of gaming that could be going on.

Paul
www.PaulRoark.com