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Matt,

do you mean detector voltage or gain? Which system are we talking about?

Regarding the photomultiplier and the influence of detector voltage, this
might be of interest:
http://en.wikipedia.org/wiki/Photomultiplier

The offset, to my understanding, is just a threshold that defines which is
the lowest intensity that will be displayed. So ideally the lowest signal
should be placed on the first intensity level (1).

Michael


> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>  Hi,
>
>  I am constantly playing around with the gain and offset settings on our
> confocal but I feel I should actually know what is actually happening to
> the hardware in order to raise the image gain.  I know that the
> photocathode in the PMT coverts photons to electrons which are multiplied
> as the electrons contact the dynodes, so does raising the gain increase
> the number of electrons and if so how does this happen? But I have no
> idea how the offset is generated.
>
>  Best wishes,
>
>  Matt Pearson.
>
>
>     --  Imaging Technician Cell Biology Division Institute of
> Ophthalmology University College London EC1V 9EL 020 7608 6857
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