[3dem] scanners

[Steven Ludtke]

Hi. We generally acquire and test any new scanner that comes out and  
claims a resolution
sufficient for use in cryoEM. Recently we tried both a Canoscan 9550  
and an Epson 750 pro.
Neither of these scanners were in even the same ballpark as the Nikon  
8000-9000's. In
particular, the MTF was atrocious. On of the important aspects of the  
Nikon is its ability
to physically adjust the focus of the scanner head. In most respects  
the Nikons match
or exceed the capabilities of the Zeiss (but not all). Neither the  
Canon or the Epson
current generation scanners are even vaguely useful for cryoEM work.  
We're using one
of them to scan gels now, though  :^)
----------------------------------------------------------------------------
Steven Ludtke, Ph.D.
Associate Professor
Co-Director National Center For Macromolecular Imaging
Dept of Biochemistry and Mol. Biol.
Baylor College of Medicine
sludtke at bcm.edu
stevel at alumni.caltech.edu
http://ncmi.bcm.edu/~stevel



On Jun 12, 2008, at 7:20 AM, Philip Koeck wrote:

> Hi again,
>
> so far I've had 1 suggestion other than the Nikon 9000 and that was  
> the
> Epson V750.
>
> I've looked at the technical specifications of the Epson on the  
> internet and
> found some strange things.
>
> There are several values for optical and hardware resolution and the
> hardware resolution differs between the x- and y-direction.
> How should one understand that?
>
> If I take one of the numbers (6400 dpi) that would mean a pixel size  
> of 3.97
> micron, which seems very small for a commercial scanner.
>
> Are the physical CCD-pixels rectangular? What does that do to the  
> MTF in x-
> and y-direction? Has anybody measured that?
>
> Is it possible to scan with the same scan-step in x- and y-direction  
> and how
> accurate is that?
>
> How many physical pixels does the CCD-array actually have?
> A very large scan-area is reported, but how is that achieved, by
> de-magnifying optically or by swathing as in the Zeiss SCAI?
>
> Does anybody have measurements of the geometric accuracy and/or the  
> spectral
> S/N-ratio?
>
> Thank you for your patience (if you've read this far),
>
> Philip
>
>
> Philip Koeck
> Karolinska Institute
> Dept. of Bioscience at Novum
> tel: +46 8 608 9186
> fax: +46 8 608 9290
> web: http://www.csb.ki.se/users/philip/philown.html
>
>
>
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