Re: 25 MP sensor of Sony

frederick wrote:
Kevin McMurtrie wrote:
The need for levels per pixel goes down as the resolution goes up. Don't forget that even really good printers may have only 1 to 3 bits per ink. 25mp is 318 ppi on a 13" x 19" print. You're doing it wrong if 12 bits per pixel at 318 ppi starts to posterize.

I'm not sure if we're on the same track here.
Posterisation (in printing) or from integer rounding when editing an image file isn't the issue.
Highlights that would be blown with 12 bit data can sometimes be recovered from 14 bit files - if they aren't too far gone. I've seen samples from D3 and 1dIII with amazing results.
Alternatively - or as well - many newer models of dslr are offering "highlight preservation" modes, that do some of this for you automatically by underexposing slightly, then boosting shadows and mid-tones in-camera for jpegs (or changing default settings for OEM raw converter saved in raw file metadata)
Having more data in the highlights in the correctly exposed 14 bit raw file in the first place is an advantage over that method as you have more room to move at both ends (presuming that the sensor is capable of recording that depth of data).
I think I have that more or less right, but I'm sure it will be corrected by someone...

The argument that 12 bits is enough challenges the assumption:
"presuming that the sensor is capable of recording that depth
of data." Consider the signal that will saturate a sensor cell,
so that more light will not increase the change. If a signal
1/4096 as large is significantly less than the absolute noise,
then 12 bits can cover the sensor's dynamic range.

Roger M. Clark has argued that the dominant noise is "shot
noise," which is in the light itself; even a sensor that counts
photons perfectly would have this shot noise. As sensor cell
size gets smaller, so does the limiting signal-to-noise ratio.
The signal is proportional to the sensor-cell size, while the
noise is proportional to the square root of the signal.
(Technically, photon arrival is well-modeled as a "Poisson
process".)

Thus the smaller the cell size, the fewer bits needed to cover
its dynamic range. I have not examined the numbers as well as
has Roger, but putting out the signal from a 5.94?m sensor cell
beyond 12 bits of precision is a bit like saying the Earth will
be four and half billion years old next Tuesday.

Capturing bright highlights and dark shadows in the same shot
is a different issue from the bits needed to cover a cell's
dynamic range. On the bright/dark range problem, Fuji's "Super
CCD HR" is a brilliant sensor design:

http://www.fujifilm.com/about/technology/super_ccd/index.html


24.8 megapixels measured to 12 good bits would be astonishingly
good. Well, technically good, on those issues. I do realize that
the shortcomings of my own photographs have little to do with
the fidelity of my cameras.


--
--Bryan
.

Relevant Pages

  • Re: Megapixels and noise
    ... is photon noise, and we need higher QE and deeper full wells ... 16-bit A/D simply is not going to provide any improvement. ... your figures for the sensor are correct, ... the sensor could have a dynamic range ...
    (rec.photo.digital.slr-systems)
  • Re: ISO 200000 ?
    ... Doesn't suggest that you can achieve 3e read noise in a sensor fitted to a dSLR. ... That way you could select the ISO after the event, and improve the effects that you are showing in your shadow assessment page. ... Compare that to your device saturation of 20 photons, which can have a maximum dynamic range of 20. ...
    (rec.photo.digital)
  • Re: 25 MP sensor of Sony
    ... Consider the signal that will saturate a sensor cell, ... 1/4096 as large is significantly less than the absolute noise, ... so does the limiting signal-to-noise ratio. ... camera is also afforded to a 24 MP camera. ...
    (rec.photo.digital)
  • Re: 25 MP sensor of Sony
    ... Consider the signal that will saturate a sensor cell, ... 1/4096 as large is significantly less than the absolute noise, ... then 12 bits can cover the sensor's dynamic range. ... so does the limiting signal-to-noise ratio. ...
    (rec.photo.digital)
  • Re: Casio extends dynamic range of small CMOS sensors to 96dB
    ... thereby extending their dynamic range. ... well capacity are could be wrong, adding noise. ... Regarding fast moving subjects, this is not an application for this ... my point is that it will be a special purpose sensor. ...
    (rec.photo.digital)