Lens Resolution (was 'Nikon Multiphot brings $3,550')

[lauriek]

This is especially obvious with microscope objectives used for brightfield applications. In this case the objective can essentially be stopped down by adjusting the diaphragm of the illumination condenser.

I'm trying to get my head around whether you could use a condenser to 'adjust the aperture' of a microscope objective while using front illumination, at this point I cannot see how that could work, probably because I don't quite understand how it works in brightfield configuration.

How does the amount of light coming through affect the aperture, or is it not the amount of light but the 'shape' of the light?

[rjlittlefield]

It's the "shape". In a microscope, one of the condenser diaphragms adjusts the width of the cone of light that passes through the subject and then through the lens. When that cone is narrower than the aperture of the lens, then the outer part of the lens essentially does not get used. It's almost but not quite equivalent to stopping down the lens. I say "not quite" because diffracted, refracted, or reflected light still has an opportunity to go through the full aperture, as in "darkfield" microscopy. Likewise for light produced in the subject itself, say by fluorescence.

See HERE for an illustration of adjusting the condenser.

With front illumination, most of the light coming back has essentially been absorbed and re-emitted by the subject, so it comes back at all angles. For this light, I don't think there's any way to change DOF by lighting.

--Rik

[PaulFurman]

Regarding the original title, high priced Multiphot, I stumbled on a Nikon Epihot-200 Inverted Metallurgical MICROSCOPE on ebay asking $10,000, with a drool-worthy description pasted from a catalog, and a little video clip

100x / 0.90
50x / 0.55
20x / 0.46
10x / 0.30
5x / 0.13

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2.5X Zoom from 0.8 to 2X
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Front and rear support of the stage, a low profile design, and a nose piece focusing system, all make fora super stable, extremely rugged instrument.

CF Infinity Corrected Optical System
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[enricosavazzi]

Hokan:

Lumiinars with a blue dot marking on them were the last Luminar series to be sold. (Blue dot supposedly identified Luminars that had the latest "treated" optics. Flare, reflectiions, color, etc.) The geometry and glass were the same as earlier Luminars. I have a mixture of both haven't noticed any significant difference. Maybe a half of a stop.

This is just a detail, but the blue vs. other colour was used to indicate the focal length of the lens, not the type of lens coatings. The 63 mm Luminar from all versions use blue color-coding, but on different items (dots, "Luminar" label etc. It is true that the blue-dot 63 mm are the latest, but there may actually be two successive blue-dot versions of this lens, and they could have different coatings:

http://goto.glocalnet.net/savazzi.net/p ... rsions.htm

Regards,