Posted by
Zoon, Peter on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Precisely-driving-several-devices-from-IgorPro-through-National-Instruments-board-possible-tp4907273p4913370.html
Dear John,
When people measure single molecule they tend to report in terms
of detected photons, probably because the amount of detected photons is a
parameter that (co)-defines the quality of the fluorescent probe they
use.
And if one
uses an APD detector you obtain a photon/s signal and then there is of course
also the method of single photon counting as a method to measure fluorescence
lifetimes.
Of course
that what is being measured are indeed photo-electrons, but some people tend to
correct the number of actually detected photons for detection
effiency.
Kind
regards,
Peter
________________________________
Dr. P.D.
Zoon
Nederlands Forensisch Instituut
Afdeling Microsporen
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web: forensischinstituut.nl
The recent release of the Photometrics EMCCD "eVolve" camera which
has the ability to output images with pixel values that correspond to
photoelectron counts (instead of arbitrary digital count units) has me wondering
a bit something. The idea behind this camera, as I understand it, is that having
images reported in terms of photoelectrons instead of counts (ie: an absolute
scale vs a relative scale) will allow a better comparison of image data between
labs around the world, and even for single user comparing images acquired with a
particular microscope from day to day. Seems reasonable to me and sounds like a
pretty good idea. What I'm confused about is that I've seen some papers in the
literature, mainly those that deal with single-molecule studies, that report
image data in terms of actual photons detected. Is there a difference, and more
importantly, can someone explain to me the advantage of using photon counts vs.
photoelectron counts?
(No commercial interest for Photometrics)
John Oreopoulos, BSc,
PhD Candidate
University of Toronto
Institute For Biomaterials and Biomedical Engineering
Centre For Studies in Molecular
Imaging
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