DF Slider Issue: Artifact

[linuxusr]

My DF slider has two click-points that “lock” it into the condenser, one for BF and one for DF.

When I lock the slider into the DF position, I have a luminescent specimen and a bold black background. The problem is that in the center of my FOV I have a large roundish blurry and brownish artifact that repeats with other specimens regardless of the specimen’s color.

Needless to say, this artifact is a deal-breaker as it obliterates a large part of my specimen.

However, if I push my slider into the condenser past it’s DF click-point, I can then remove the artifact from my FOV. When I do that, the quality of my DF image is slightly degraded, adequate, but no longer great. I get the best image when the artifact is present but only in the area that the artifact excludes. If the manufacturer put the click-stop in the location where I get the artifact, that doesn't make sense.

With my turn-screws, I can move the stop orthogonally along the x axis. When I move the stop all the way to the left or all the way to the right, I can de-center it but not remove it.

Either I’m doing something wrong or the slider has a defect. I hope that it’s the former.

[hans]

Maybe condenser height or centering is off? As you close down the field iris do you see the leaves come into view symmetrically around the field of view in sharp focus?

With a little practice taking photos with a smartphone hand-held through the eyepieces can work quite well and would probably help diagnose issues like this before you figure out a dedicated camera setup.

[hans]

Just noticed your signature line... positioning the condenser based on the field iris is steps 11-14 in section 5.4 "Adjusting the Transmitted-Light Brightfield on the Full-Köhler Microscope" in the manual.