[3dem] magnification question

[Farzad]

Dear all,

This is a constant discussion topic between the users of microscopes. It
always used to take one complete session of my classes to discuss about the
significance of "magnification".

The magnification is a real measure but it does not have any numerical
significance for us. It is like asking how much is the current inside a
lens!

Let's consider the magnification as a name, i.e. a string type value, for a
certain optical configuration of the projection system. Let's name 100000x
james and 50000x jones. Nothing happens.

The important measure is the pixel size for the digital image recording
systems and the image dimension (real image width for example) in the
analog formats.

Historically it was a place of debate in the Philips EO (later fei and
nowadays TF) microscopes. The magnification was changing depending on the
viewing plane: lower for camera rolls and higher for sheet films. But in
older Zeiss EMs we never had this consideration.

Hereby, I also draw your attention to the following standard:

ISO 29301:2017, Microbeam analysis — Analytical electron microscopy —
Methods for calibrating image magnification by using reference materials
with periodic structures

It is a precise method for calibrating the magnification in TEMs, however
it may not be very easy to implement. The previous version was not
practical at all,  especially for lower magnifications and I hope they have
addressed the issues with the previous version in the newer one.

So in general, the term magnification is just for internal use. It is just
for describing a lens configuration, and finally it changes from the sensor
to your printer to your monitor.

Best Regards,

Farzad Hamdi,

University of Halle



On Tue, Jun 23, 2020, 19:50 Morgan, David Gene <dagmorga at indiana.edu> wrote:

> Hi,
>
>
>     Does anyone happen to know whether the magnifications reported by a
> Talos Artica are supposed to be "mag on the viewing screen" or "mag at the
> film plane"?  We clearly have a serious issue with the calibrated
> magnifications on our microscope, but I just recalibrated it and got more
> or less the same lousy magnifications.  I'm trying to understand our
> issues, and knowing what the microscope thinks it is reporting would be
> helpful.  Thanks in advance.
>
>
> --
>     politics is more difficult than physics.
>                                              A. Einstein
>
>             David Gene Morgan
>         Electron Microscopy Center
>              047E Simon Hall
>              IU Bloomington
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