[3dem] Falcon 3 output

[Wim Hagen]

David,

The conversion rate for counting mode is mentioned in a datasheet of the camera, as a PDF file on some DVD that came with the camera/system.

Best,

Wim

> On 6. Jan 2023, at 19:06, Morgan, David Gene <dagmorga at indiana.edu> wrote:
> 
> Hi,
> 
> I have a stupid question about the MRC files output by our Falcon 3 camera.  I just acquired a set of movies in counting mode where the total dose should be on the order of 25 electrons/ A^2, spread over 22 frames.  My pixel size is just under 1 A, so my images should have on the order of 20 - 25 electrons per pixel.  At least the average over all the pixels after summing or motion correction should be close to that...
> 
> When I examine the MRC files output by EPU, I find the following min/max/mean for an example acquisition:
> file with fractions (22 frames): min = 0, max = -1, mean = -2 (obviously bogus values)
> fractions after recalculating min/mix/mean:  min = -23, max = 549, mean = 108.27
> summed image (non-motion corrected single frame output by EPU): min = 1239, max = 3809, mean = 2382
> My stupid question:  How do these numbers relate to what should be the counted number of electrons that hit the specimen?  
> 
> I suspect that I am seeing some stupid effect of an "average counts per electron" in these images, but I had previously (and I suppose foolishly) assumed that in counted mode images, one count would mean one electron...
> 
> Thanks for any input you can offer, and Happy New Year.
> 
> -- 
>     politics is more difficult than physics.
>                                              A. Einstein
> 
>             David Gene Morgan
>         Electron Microscopy Center
>              047E Simon Hall
>              IU Bloomington
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