Re: Why not make the sensor larger?

Alfred Molon wrote:
But for instance in CMOS sensors charges do not have to travel a couple of cm along a row of pixel in a CCD manner - they can be addressed individually. The Janesick article does not state that readout times for individual CMOS pixels are huge (in fact no figures are provided).

In any case, the proof that my suggestion actually works is the fact that a such a multiple read sensor actually exists:

http://www.toshiba.com/taec/news/press_releases/2007/assp_07_466.jsp

Also have a look at the PDF white paper at
http://www.techonline.com/learning/techpaper/197700819

This device (or one very much like it) was already
discussed in the newsgroup. Let's see, 96 dB
with 2.2 micron pixels? 96 dB is magically exactly
what 16-bits is (and note you would need at least an 18-bit
converter to deliver 16 bits of real dynamic range).
And 72 dB is 12-bits, as if anyone really believed
2.2-micron pixel cell phone cameras actually delivered
12 bits of dynamic range. Then let's talk photons.
To get 96 db of dynamic range, you need to collect
enough photons: 65535*(read noise in electrons).
So if read noise matched the current lowest read noise
consumer dcams available (~3 electrons in Canon 1D Mark III
if reports prove out; ~3.9 electrons in 30D, 1D Mark II),
then the little cell phone 2.2-micron pixels need to collect
at least 3 * 65535 = 196,605 photons. Typical pixel
storage is 1,000 to 2,000 electrons per square micron,
so the Toshiba technology is over 40,000 electrons/sq. micron.

What's fishy about this report? The previous thread on this,
if I remember correctly, concluded the marketing department
got carried away converting A/D bits and didn't
focus on reality. We'll see when (if) the device
actually shows up on the market and eclipses top
end DSLRs with large pixels with dynamic ranges that
currently don't quite reach 72 dB (12 bits).

Roger
.

Relevant Pages

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