[3dem] Falcon 3 output
Morgan, David Gene
dagmorga at indiana.edu
Fri Jan 6 10:06:39 PST 2023
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:
1. file with fractions (22 frames): min = 0, max = -1, mean = -2 (obviously bogus values)
2. fractions after recalculating min/mix/mean: min = -23, max = 549, mean = 108.27
3. 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
812 856 1457 (office)
812 856 3221 (3200)
https://urldefense.com/v3/__http://iubemcenter.indiana.edu__;!!Mih3wA!E-FcoZUZdcr3llQ_tQ7nra_aC45SHHOofl5vsdk4RilKOYWBacUzdW1K8BzGLp3U7LbXIfTjwt3E1eA8hKRTl-Y$
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