[3dem] phosphur thickness and CCD resolution
Bill Tivol
tivol at caltech.edu
Mon Apr 28 15:44:09 PDT 2008
On Apr 10, 2008, at 1:59 PM, acheng at scripps.edu wrote:
> Does anyone have any idea how much resolution loss we might get when
> the CCD camera sensitivity is increased by about two-fold?
>
> We recently replace the CCD chip and the phosphur on top of our
> 4k Gatan
> camera. Gatan technician said that the phosphur is thicker, and we
> observe that our camera sensitivity has gone up. The question
> would be
> whether this will affect the MTF or the usable resolution of our
> camera by
> similar factor, worse or not as much.
Dear Anchi,
When we measured this--crudely; we just looked at how many pixels it
took to go from bright to dark across an edge--we found ~50% increase
in point-spread width. Whether this makes usable resolution better
or worse depends on several factors, such as S/N, image contrast,
whether the pixel size is small compared to resolution, and other
properties of both specimen and camera. In our case, we found better
results with a brighter screen, but YMMV.
Yours,
Bill Tivol, PhD
EM Scientist
Electron Cryo-Microscopy Facility
Broad Center, Mail Code 114-96
California Institute of Technology
Pasadena CA 91125
(626) 395-8833
tivol at caltech.edu
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