[3dem] Zeiss SCAI/ ZI Photoscan discontinued

[Steve Ludtke]

We originally used an in-house modified glassless holder, and in fact, that's
what we used on the 4A GroEL structure. Eventually we had too many problems with
films that weren't flat, and built some glass holders using the FH869 holder as
a base. We found that, while they were ok, there was variation in quality in the
Nikon glass holders, and one would observe focus variation across the film. By
carefully measuring the MTF across the film, and using varying numbers of pieces
of scotch tape, with epoxy once optimized, we managed to get a glass holder that
had very good performance across the film. You do lose some fraction of the
film, perhaps 10-15%, but we simply accept this limitation.

----------------------------------------------------------------------------
Steven Ludtke, PhD              |        Baylor College of Medicine
sludtke at bcm.tmc.edu             |     Associate Professor & Co-Director
stevel at alumni.caltech.edu       | National Center For Macromolecular Imaging
V: (713)798-9020                |    Dept of Biochemistry and Mol. Biol.
F: (713)798-1625                |
                                |             Those who Do, Are
http://ncmi.bcm.edu/~stevel     |         The converse also applies

On Thu, 15 Nov 2007, James Conway wrote:

> Steve,
>
> > We turned our Zeiss off about 3 years ago and haven't used it
> > since. We now use
> > a set (they only cost ~$1k each) of Nikon 9000's. With a properly
> > machined
> > holder (the ones they ship require some minor modifications), we
> > found that they
> > outperformed our Zeiss in most respects. There is also a
> > publication by Typke
> > describing some technical evaluations of these scanners.  Whenever
> > a new
> > consumer grade scanner with apparent technical specifications that
> > would make it
> > useful to cryoEM comes out we evaluate it, and so far none of the
> > other
> > available 'consumer' grade scanners has performed as well as the
> > Nikon (even
> > though on paper some look better).
>
> I would use the Zeiss, but I can't justify the cost - even
> maintenance is more than the Nikon! - so I bought a Nikon. I also
> bought the glass-cover holder which allows the film to fit without
> modification, and holds it flat. Of course, you can only scan about
> 1/2 of the area, but turning the film around gives you up to 2/3 the
> total area. The Zeiss, at least, gives you the whole film in one
> file, and I thought the later ones (like I had in Grenoble) were
> better than the early ones (like we used in Alasdair Steven's lab at
> the NIH).
>
> Did you ever try out the glass holder in the Nikon 9000?
>    FH-869G  "Film-Holder 869 Glass-covered" for medium format
> negative film
> If you haven't seen it, an image is here (can't find one on the Nikon
> web site):
>
> <http://www.bhphotovideo.com/c/product/218836-REG/
> Nikon_9241_FH_869G_120_220_Strip_Film.html>
>
> I would be interested to hear more of your holder.
>
> Best regards,
>
> James
> ----------------------------------------------------------------------
> James Conway, PhD.,
> Department of Structural Biology
> University of Pittsburgh School of Medicine
> Biomedical Science Tower 3, Room 2047
> 3501 5th Ave
> Pittsburgh, PA 15260
> U.S.A.
> Phone: +1-412-383-9847
> Fax:   +1-412-648-8998
> Email: jxc100 at pitt.edu
> Web:   http://www.pitt.edu/~jxc100/
> ----------------------------------------------------------------------
>
>
>