Re: DIC On An Amateur Budget

Dear Mr Cunningham,

I have to disagree with you again.

Olympus not only builds a variable NA for 60x magnification but also
for 100x magnification. I own both of them and are very familiar with
their performance. They perform exceedingly well with Olympus' DIC.
I have given a link to pictures taken by me with the 60x in a
previous post.

I reproduce the links here. They have been tested and the images
are only a click away from you:

http://www.mikroskopie-forum.de/read.php?2,31059,31059#msg-31059
and at
http://www.mikroskopie-forum.de/read.php?2,32440,32440#msg-32440 .

Please look at the pictures and then tell me what is wrong
with the performance. I and the remaining readers of this long thread
will, I am sure, be most interested in your comments.

About mag and NA I may take you up another time. One thing at a time
is the best way to resolve a problem

GR




"Kevin Cunningham" <smskjv@xxxxxxxxxxxxxx> wrote in message
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"NoSpam" <NoSpam@xxxxxxxxxxxxxxxx> wrote in message
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Dear Kevin,

Again we do not agree. We had a difference of opinion regarding
the "twitching" of Pasteur's left eye. You thought it was due to his
use of a monocular scope. I am quite certain that the record shows
the Pasteur suffered a stroke at age 46 which paralyzed his left side
and I know that monocular scopes do not cause twitiching of any eye.

Now we have the issue of magnification versus NA. Of course
NA is an important parameter. But magnification plays an essential
role when one wishes to image an object of a given size upon film
or CCD of fixed dimension. When one addresses this issue one
can't do it without using magnification. This should be easy to
understand.

If one addresses resolution it is esssential to take NA into account,
but even then magnification enters, because the size of a resolution
element when projected upon film or a CCD depends upon the
magnification the resolution element undergoes.

Now this is all very obvious and is not really by itself part of this
thread which was, if I remember correctly, how one can have
low cost DIC for the observation of protozoa. One way to
lower the cost is to narrow the range of magnifications one
wishes to purchase into. One setup costs a lot less than
multiple setups and if one chooses the most useful one, one
can save money.

DIC components are purchased and installed according to
magnification. Please consult an Olympus spec ***. There
you will find that for example a Nomarski prism is sold not
by NA, but by magnification. I quote:
"U-DP40;Nomarski Prism for 40x UPLFL......."
Similar descriptions are given for all other magnifications.

In fact Olympus objectives have iris diaphragms which vary NA
over a wide range ( 0.65 to 1.25 for the 60x). The DIC setup is
exactly the same throughout this range.

In summary money can be saved by choosing a DIC setup
most appropriate for the task at hand. Magnification plays an
important role in determining what this setup should be.

GR.


Allow me to disagree with you. Magnification was not used by some makers
including Zeiss until approximately 1905. They used A, B, C, etc. While
mag is an easy way to point out what objective you are discussing it still
doesn't say much about what the obejctive does.

My training was primarly from Zeiss. Their point is well taken, NA gives
you resolution, there is no other way to define resolution, see Abbes
equations.

Now minor points, you aren't supposed to use variable NA objectives with
Nomarski. Olympus doesn't build a 60X that really works with their
Nomarski, I tried.

Thanks,

Kevin Cunningham
SMS




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