Archived posting to the Leica Users Group, 1999/12/10

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Subject: [Leica] Re: Digital Photography(slightly OT)
From: Jim Brick <jimbrick@photoaccess.com>
Date: Fri, 10 Dec 1999 08:48:35 -0800

What the guy didn't say is that it takes four 3x3 micron cells to make up a
single color pixel on a digital sensor. 3+3=6, 6x6=36 sq. microns. Hardly
even close to what film can do. Average grain size in high resolution film
is 1 square micron. 1 vs 36... big difference. And there is about 10
billion silver halide molecules in this grain that can individually be
converted to silver via development. We have, right here in house, some 6
megapixel Philips sensors. They do not even come close to 35mm film. I
posted a long dissertation on grain size, latent image, developer action a
while back. It is clear that a complete technological change will have to
happen for digital to be as good as film. To come close to 35mm film, a
digital camera would have to produce a raw RGB file of 65 megabytes. The
sensor size would have to be 256 megapixels in size. Not likely with
current technology.

If you want to make the best digital prints, use film, scan the result on a
very high resolution scanner, then go to print via LightJet, Iris, high end
Epson, etc.

Jim



At 11:30 PM 12/9/99 -0500, Andrew S Jordan wrote:
>For you digital photo enthusiasts, the latest research development - fresh
>from the annual semiconductor device conference- is attached.
>
>regards, Andrew Jordan
>
>
>
>----------------------------------------------------------------------------
>---------------------------------------------------------------
>
>
>
>    www.cmpnet.com
>The Technology Network
>
>
>Philips CCD rivals 35-mm quality
>By Peter Clarke, EE Times
>Dec 9, 1999 (9:04 AM)
>URL: http://www.eetimes.com/story/OEG19991209S0012
>
>WASHINGTON  Digital still cameras could rival the image quality of 35-mm
>film photography within a couple of years due to a charge coupled device
>(CCD) image sensor with over six million pixels developed by Philips
>Semiconductors (Eindhoven, Netherlands). Herman Peek, a senior scientist at
>the company, presented a paper on the prototype device at this week's
>International Electron Devices Meeting. "This is the largest number of
>pixels and the smallest pixel size for a digital still camera ever published
>in the world," Peek said during the presentation of his paper.
>
>Although the prototype sensor is monochrome, and the use of red, green and
>blue filters would reduce resolution to 2 million tricolor pixels, Peek said
>the small size of individual light sensing elements, 3-micron x 3-micron,
>would allow such a sensor to rival small format film photography.
>
>"We are approaching the grain size of film, which is about 2 microns
>diameter, but image quality is also determined by the quality of the lens.
>The same thing effects CCD."
>
>Images produced using the sensor and displayed by Peek, albeit through an
>overhead projector system, were indistinguishable from images obtained from
>film. Individual hairs could been seen on the heads of head-and-shoulder
>portraits, which prompted congratulations from the audience.
>
>Peek said he expects to see a similar high-resolution CCD sensor in
>production within about two years, although it might include fewer pixels.
>"I don't think we will go to more pixels," he said. "We are already asking,
>'Is six million too much and are we adding cost unnecessarily?' Perhaps five
>million or four million is the right amount."
>
>For a 2/3-inch format, Peck showed that the pixel size was on the limit of
>lens resolution, although the device could also be used for lens-less
>applications.
>
>The Philips CCD is built using a 0.5-micron CCD process operating at 14
>volts and has an active area of 2,048 active lines and 3,072 active
>measuring 9.11 mm x 6.07 mm. The sensor has a dark current of 800
>picoamperes/centimeter2 and a dynamic range of 63 dB. In his paper, Peek
>also discussed how novel techniques had been used to overcome problems with
>dark current suppression.
>
>The development of a high-resolution sensor using CCD technology represents
>a fight back by the technology against a challenge it faces from lower cost
>CMOS image sensors, which also allow the possibility of including signal
>processing and logic circuits on the same die.
>
>"CCD will always be expensive in comparison with CMOS image sensors," Peek
>said. "CCD can't compete with CMOS on price but it can on quality, and image
>quality is very important to consumers."
>
>Copyright 1998 CMP Media Inc.