On 2012.09.21 17:34 , Martin Brown wrote:
On 21/09/2012 21:43, Alan Browne wrote:
On 2012.09.21 03:12 , Martin Brown wrote:
On 20/09/2012 16:47, Wolfgang Weisselberg wrote:

So there's no variation in noise between camera types, sensor
technology and pixel sizes? There's no different JPEG denoising
between cameras?

Cameras making JPEG files are only writing the JPEG stream. There might
be tiny differences in the exact sensor demosaicing code but that will
largely be hidden when the file is saved JPEG 2x1 chroma subsampled. I'd
give better odds for recognising a full RAW file with all the sensor
calibration info still in it.

What W said is the real point of it: what leaks through the physics into
the image - raw or JPG - will fingerprint the camera design. Look at
enough image samples and it comes out.

Sensor noise might allow you distinguish a few *very* old and thermally
noisy cameras but that is about all. The odd camera has insane default
settings usually oversharpened which would also be easy to spot.

Given the statistical methods used by them even new "quieter" cameras
will in the end give up their signatures - even via JPG.

Not a chance after JPEG encoding.
Too much of the noise signature is lost.

It may be compressed into a narrower range and some will disappear in
the JPG encoding, but some will remain (all JPG's show noise from the
camera). As such enough sample images from a given model will reveal
noise attributes traceable to that camera model (or range of cameras
with the same sensor/a-d/n-r chain).

--
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