T3D Re: T3D Re: digital camera resolution

[michaelk@xxxxxxxxxxxxxxxxxx (Michael Kersenbrock)]

> Just taking the base numbers, I think there is something fishy here.
> Supposing we accept the guy's 40 lpmm in a 35 mm camera (fair if you
> have any depth of field) then the image has 24*36*40^2 or 1,382,400
> pixels.  If we take a 640 x 480 camera and throw in Nyquist (you have
> to have two pixels to image one black and one white bar) you have 340
> x 240 or 81,600 pixels of the same nature as the 35 camera's pixels.
> (Probably I should have done this the other way - multiplied the 35
> camera's resolution by two to get the digital camera pixel equivalent.)

And if one reads that article in EDN that I referenced a while ago,
one sees that the digital camera's "pixels" often are black-magic 
computation based ones.  Example: One of the cost savings used in some of 
them is the use of VCR CCD's instead of camera CCD's.  The VCR CCD's are
produced in volume and are cheaper.  Difference is that 
the VCR ones have long aspect ratio "pixels", so they manipulate the data to
get three picture pixels out of one "CCD pixel" in its long-direction.  
Another example:  How does the color information get captured?  In the
best case, they have filter stripes and the number of pixels is essentially
one third of those on the CCD chip because it takes three to capture each
of three primary colors.  But some use two colors and "fake" the third in
software.  Some use black-magic formulae to conjure up the colors from other
partial acquisitions, biasing the colors in what they perceive to be that
which is desirable by the users (well, I guess the film makers do this too).

This isn't to say that the high end ones can't be very good, especially the
"scanner" technology ones that work only for still-photographs.  However
that article is very enlightening.  Of course, it's mostly Kodak technology
and may not be applicable to every camera at all price ranges, but it 
definitely causes one pause.  :-)

They're getting there, but I suspect it hasn't happened yet.


Mike K.


> 
> John B
> 
> 


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