Re: magnification of 250

On Aug 19, 6:54 pm, "helio" <forbid...@xxxxxxxxx> wrote:
"Fred" <mb...@xxxxxxxxxxx> wrote in message

news:20f318a1-26e9-46db-b339-0a0a548e08b1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

To follow up on what Heini was saying.  The resolution of the human
eye is about 0.2 mm, give or take a few tenths.  A 1000x magnification
gets you to 0.2 micrometers.  The resolution of the microscope,
limited by diffraction of light, is a bit more than 0.2 micrometers.
So magnifications above 1000x are useless, empty magnification, except
for specialized cases as outlined by Kevin Cunningham.  As he
emphasized, the Numerical Aperture of a microscope objective
determines resolution, not the magnification.

Now I understand what heini was saying about 1000X magnification, thanks.
And I imagine that is not easy for physicists to cheat the laws of
diffraction :)

Helios,

There is a rule of thumb that a lot of people use, never have more
than 1000 times the NA as magnification. There is a limit at around
1.4 - 1.45 NA if you are using conventional immersion media so you
shouldn't have more than 1,400 power.

Some powers are just popular, 40X for instance. If you tried to sell
a bio objective that was 60X rather than 40X you would have some
problems, every one selling 60X objectives sells 40X objectives.
Popularity is the primary reason why some powers are sold and some
aren't. For instance the NC 40X isn't popular even though it's
necessary. See any hematology dept.

Making an objective has a lot to do with making one that will sell to
users.

Thanks,

Kevin Cunningham
SMS
.

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