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Christophe,

I believe the Andor EMCCD cameras have a feature that allow you convert pixel counts directly to photoelectron counts (or photon counts if you indicate the emission wavelength). It's called count-convert mode, or something like that. 

If you can't get that to work, Nico Stuurman has outlined a very simple procedure to directly measure the e-/ADU value of your camera using MicroManager (any image acquisition software can be setup to do the same thing):

http://valelab.ucsf.edu/~MM/MMwiki/index.php/Measuring_camera_specifications

With the EM gain set to 1, I suspect that you'll get something between 5-15 e-/ADU, depending on the pre-amp setting you've chosen. At least, those are the numbers indicated on the calibration sheet of the camera I'm using.

Cheers,

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



On 2013-09-03, at 9:03 AM, Christophe Leterrier wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> *****
> 
> Hi,
> 
> I'd like to evaluate the localization precision for single molecule
> experiments. I need to convert the acquired signal into a number of
> photons, using knowledge of the camera gain. Anyone would know what is the
> typical gain (I mean the e-/ADU gain before taking into account the EM
> gain) for an Andor Ixon 897 camera, using the 10 MHz readout and the gain
> set to 1?
> 
> I'll try to ask Andor for my specific camera but that would be great to
> have a number to try and see if my calculation is not too far off.
> 
> Thanks,
> 
> Christophe
> 
> --
> Christophe Leterrier
> Researcher
> Axonal Domains Architecture Team
> CRN2M CNRS UMR 7286
> Aix Marseille University, France