Thoughts on Kohler,

[BrassCat]

Hello the forum, I have now read several articles on Kohler illumination. Still
trying to wrap my head around it, and read again. I can comprehend somewhat
what is being said, but still struggling to visualize it working! I will have to
study the definition of some of the words used.

OK, so I am new at this. The micro I bought was damaged somewhat, but looks
like repairs are within my mechanical skills, the price was right.

Question then about kohler illumination. Seems it was designed to eliminate the
problem of an uneven light source, like the filament of the bulb from showing up
in microscope photos, or even viewing by eyepiece. With that so, the bulb in
my microscope, Swift SRL, is spherical, half of it aluminized to be reflective, the
other half frosted to provide a more diffused light that looking or projecting the
filament from the bulb. It is set up to use kohler illumination, has two irises and
condenser lens.

Therefore I would think that even in Kohler illumination, a diffused light source
is still better. This seems to be at odds with the reason presented for the creation
and use of kohler illumination.

Shedding light on this would be appreciated. thanks so much.

Stan

[apochronaut]

I usually establish Köhler illumination but use a diffusion filter for low magnification objectives; 2.5x and 4x, seldom for anything above. I find that it has a slightly adverse effect on contrast, softening it somewhat but that can be a benefit with a scanning objective, where the softened contrast can assist the eye in searching.

I also have microscopes with otherwise really fine condensers and optics, albeit somewhat older and I often don't bother with Köhler when using them. Probably too much attention is put on it's importance because in fact it is simply a technique to overcome the problems associated with a filament light source( newly arrived just prior to the adoption of the technique) and a second rate but cheap condenser( abbe).
It has to be kept in mind that both Ernst Abbe and August Köhler brought their contributions to Zeiss not too long after the Zeiss firm had established themselves as being obverse to the value of an understage condenser at all.