The noise is variation in the signal,
which prohibits your ability to discriminate between signals varying less than
this. Dividing the FWC by less than this does not add to the ability to detect
differences, even though technically the bit depth of the image could be
higher. Equally, dividing by greater than the noise results in “binned”
values in the bit range which could, technically, be accurately detected as
different values if the bit depth were greater. Typically, if a camera has a
noise of 7 electrons and a FWC of 21,000, then the dynamic range (your ability
to discriminate to signals of different intensity) is 3000. In this case, the
manufacturer would set the bit-depth at 12 (4096).
The offset is subtracted from the full
well capacity, this is set by the manufacturer (typically 50-200 counts in the
image).
There are many more detailed descriptions
of this in various books (Video Microscopy by Inoue and Spring for instance).
Hope this helps
Paul S. Maddox, PhD
Assistant Professor
Institute for Research in Immunology and Cancer
Dept of Pathology and Cell Biol, U. de Montreal
Courier:
2900, boulevard Édouard-Montpetit
Pavillon Marcelle-Coutu, Quai 20
[hidden email]
Ph: 514-343-7894
Fax: 514-343-6843
From:
Sent: Wednesday, July 23, 2008
10:46 AM
To: [hidden email]
Subject: Dynamic range of a CCD
Hi everybody,
I don't understand why the dynamic range of a CCD is
defined as the full-well capacity divided by the camera noise, and not minus
the camera noise.
Thanks a lot for your help,
Laurent.
___________________________________________
Laurent Gelman, PhD
Friedrich Miescher Institut
Facility for Advanced Imaging and Microscopy
WRO 1066.2.16
Maulbeerstrasse 66
CH-4058 Basel
Tel.: 061 696 43 38 / Cell phone: 079 618 73 69
| Free forum by Nabble | Edit this page |