What is this fascination with iso6400?

Started Feb 11, 2013 | Discussions thread
Detail Man
Detail Man Forum Pro • Posts: 16,688
Re: What is this fascination with iso6400 ?

John Sheehy wrote:

DigitalPhilosopher wrote:

EDIT 2: Like someone said, would 600.000-something ISO be enough? Or will we suddenly discover we need 1 million?

1 million is not far-fetched at all. In fact, the only reason I can't get a usable, small web-sized ISO 1 million from my 6D is because of the banding noise; horizontal lines running across the image. If I took some opaque black paint and covered a few hundred columns of pixels on both edges of the sensor, I could use the data from these masked areas to get rid of most of the banding noise. The camera only uses less than 100 masked pixels on the left edge of the image, and that simply is not enough to remove banding at ISO 1 million.

Some day we may have commercially available cameras that are photon counters, and then ISO 1 million will be much more usable than it is today.

Hi John,

The input-referred noise of the MOSFET source-followers that act as unity-gain voltage amplifier buffers the photo-sensing material in photo-sites is not outstanding (compared to JFETs or bipolar transistors). Lower Drain-Source voltages (and operating currents) and lower Gate-Source input currents help matters somewhat - but only so much. Perhaps to something a bit better than 80 dB SNR.

Basically true for decades, since their initial development. Such performance characteristics would seem to imply some upper limits on the amount of post-amplification that is practicable.

What "quantum leaps" (in semiconductor noise characteristics, and/or system architectures) could overcome the basic limitations presently imposed by the very first "link in the chain". How would a "photon counter" substantively differ from the presently existing system architecures ?

DM...

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