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Gabor,

I think the reality is that a fluorescence microscope (especially operating in the confocal mode) is actually a very inefficient light filtering device. There is a passage from a book chapter written by Kennith Spring in the book Digital Microscopy (3rd Edition) that states:

"The geometric constraints also imposed by the numerical aperture of the objective lens as well as the inevitable losses in the optical train of the microscope lead to a loss of 80% or more of the original fluorescence signal. Depending on the properties of the detector, the resultant electronic signal may represent as little as 3% or as much as 16% of the total fluorescence emission.”

As you say, the exact value depends on the detector, the optics of the system, etc.

Cheers,

John Oreopoulos
Staff Scientist
Spectral Applied Research
Richmond Hill, Ontario
Canada
www.spectral.ca


On 2013-11-07, at 7:33 AM, Csúcs Gábor wrote:

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> To join, leave or search the confocal microscopy listserv, go to:
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> 
> Dear All,
> 
> I made a quick search but found nothing really useful. My question is the
> following: does anyone have some data/literature how efficient microscopes
> are in detecting the photons of a fluorescent sample? Obviously the NA and
> the QE of the camera (plus the performance filters/dichroics) are
> important factors but taken e.g. A single molecule experiment with a 1.49
> NA objective and a back-illuminated EM-CCD what ration of the emitted
> photons really reach the detector? Of course the transmission of the
> objectives and other lenses in the microscopes can vary but is there still
> an estimate?
> 
> Thanks     Gabor