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Mark,

    By my reckoning it's after 4 in the morning in Auckland - what are
you doing replying at this hour?  (By the way, I'm in Taiwan, not Oz).

                                   Guy

Optical Imaging Techniques in Cell Biology
by Guy Cox    CRC Press / Taylor & Francis
     http://www.guycox.com/optical.htm
______________________________________________
Associate Professor Guy Cox, MA, DPhil(Oxon) 
Australian Centre for Microscopy & Microanalysis, 
Madsen Building F09, University of Sydney, NSW 2006 

Phone +61 2 9351 3176     Fax +61 2 9351 7682
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-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]]
On Behalf Of Mark Cannell
Sent: Friday, 17 June 2011 2:41 AM
To: [log in to unmask]
Subject: Re: averaging vs. accumulation for noise reduction - is there a
difference?

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It also depends on how the readout  bandwidth is controlled for
different scan speeds...

Cheers
On 16/06/2011, at 5:26 PM, Stanislav Vitha wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> *****
> 
> Hallo,
> this is a very basic question, but I cannot figure this out from what
I have 
> been reading, so a simple explanation for a non-physicist would be
much 
> appreciated:
> 
> Is there a real difference in the improvement of the signal to noise
ratio 
> between frame averaging (or accumulation) and longer dwell times
(slower 
> scan) for a point-scanning confocal witrh a PMT detector?
> 
> For instance, using single point scanning confocal, 12-bit
acquisition.
> 
> a) averaging (or accumulating) 5 frames, 4 microseconds per pixel
> b) acquiring a single frame, 20 microseconds per pixel
> 
> Assumptions: 
> no saturation of the detector;
> stable environmental conditions, no focus drift, etc
> 
> Would it matter (for the dfference between the two scenarios) if it
was analog 
> detection or photon counting detection?
> 
> I will run this little test later, but I am curious what you think. 
> 
> I thought that at least for the photon counting mode, the two
important 
> factors would be the dark counts and the total number of counts
detected, so 
> whether it is acquired in one scan or in 5 scans, it should be the
same. My 
> camera expert here insists that the averaging scheme will give better
noise 
> suppression.
> 
> Thanks!
> 
> 
> Stan Vitha  
> 
> Microscopy and Imaging Center 
> Texas A&M University

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