[Leica] Re: For those who think film will be dead...

[Alexey Merz <alexey@webcom.com>]

>Jim Brick:
>> Current semiconductor chip geometry = .18 micron
>> It could possibly go to .1 micron.

Anthony Atkielski:
>>Hmm... see below.

>> To put things in perspective, the volume of an "average"
>> silver halide grain is .0000000000001 cubic cm.

>That's a cube that measures 0.00001 centimeters on a side, 
>which is 0.1 micron. Hey... that's the same size as the 
>semiconductor components you mentioned above!


Frankly, these considerations are not really germaine to a 
discussion of detector resolution because the smallness of a 
CCD pixel is limited by the need to store a relatively large 
number of electrons. From the modern microscopist's bible:

"The diodes in consumer-grade 2/3 inch CCDs usually range from 
about 7 to 13 um in size and hold a stored charge of 50,000-
150,000 electrons. A rough calculation of potential-well storage
capacity may be obtained from the area of a diode multiplied by
1000. For example, a diode of dimensions 10 x 10 um will have a 
full-well capacity of about 100,000 electrons."

(Inoue & Spring [1997] Video Microscopy: the fundamentals. 
2nd ed. New York: Plenum Press. ISBN 0-306-45531-5.)


In other words, without substantially degrading the dynamic 
range of the CCD, current technology provides no obvious way to
make CCDs with pixels smaller than 5-10 um in diameter. 
And it is extremely difficult to make very large CCDs inexpensively; 
moreover, doing so will impose the same requirements for large 
heavy lenses (with big image circles) as medium format film does. 

So make your choice: the dynamic range of CCDs or the resolution
of silver emulsions. Choose the latter, and film wins. And remember - 
film is improving at least as fast as CCDs are. 

The bottom line is that Moore's law governs digital image STORAGE
and MANIPULATION but NOT digital image ACQUISITION. We are already 
surprisingly close to the theoretical resolution limits for compact,
handheld digital CCD still cameras.

- -Alexey