At 10.19 fm 98-04-21 -0400, Jeff Reece wrote:
>Dear Martin:
>
>I think using the words "virtually never" to describe the occurence of
>12-bit confocal S/N is certainly appropriate if the manufacturers refuse
>to give users this option.
Good afternoon.
I should like to comment on this issue from a technological point of view.
I sometimes met the attitude amongst life-scientists "The more bits-the
better". This simple relation is, unfortunately, often wrong.
We've studied this problem by computer simulation as related to
quantitative CSLM measurements applying ratio-imaging dyes and published as
a "further result" in Cell Calcium 22(4):287-298, 1997. To tell it in a
nutshell: As long as the number of detected photons per pixel is less than
256, it does in principle not make any sense to have more than 8 bits
(since an eight-bit value, i.e. a one-byte integer, defined as an unsigned
char can max. be 255 = pow(2.0,8.0) -1 ). Also, the human eye is, as far as
I know, on the "limit of its specification" with 256 grey-values (hence,
b/w screens usually display grey values 0-255). If, however, the numbers of
detected photons per pixel exceed 255, and if the detected pixel intensity
values are converted to floats or even doubles BEFORE any further
processing of the raw-data images is done, even an algorithm as
noise-enhancing as the ratio-imaging algorithms does NOT depend in any
noticeable way on whether the raw-data images have been detected digitizing
into 8bits, 12bits, 16bits, a.s.o.
Best regards,
Johannes Helm
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Paul Johannes Helm
Mail Address: Institute of Basic Medical Sciences
Department of Anatomy
P.O. Box 1105 - Blindern
N-0317 Oslo
Norway
Visiting Address: Institute of Basic Medical Sciences
Department of Anatomy
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N-0372 Oslo
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Voice: +47 22851159
Fax: +47 22851278
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WWW: http://www.uio.no/~jhelm
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