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PostPosted: Mon Oct 02, 2017 10:21 pm 

Joined: Mon Sep 18, 2017 10:12 pm
Posts: 22
This is probably a silly question but just thought I would ask anyway ... Is it possible to change the nose-piece to a DIN then use an adapter with a light path around it so as to use RMS objective for vertical illumination? If this was possible it would save the huge extra cost of EPI/APO infinity objectives.

PostPosted: Tue Oct 03, 2017 2:51 am 
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Joined: Sat Jun 20, 2015 3:57 am
Posts: 2540
Location: Houston, Texas
Sorry, I am not clear about your intent and do not understand your question(s).

RMS is a thread diameter standard of common biological objectives. Edit: many epi objectives do have wider thread size to provide "ring of light".

DIN is modern parfocal length standard for objectives. A nosepiece does not have much to do with parfocal length.

What did you mean by "light path around it"? Did you mean epi darkfield? It is routinely use in epi illumination systems. Not easy to DIY though.

Epi objectives do not have to be infinity corrected, though infinity system allows more chance of adding more intermediate components. They can have finite tube length as well, 160, 190, 210 or 215 mm tube length, to name a few. In generally, best not to mix infinity optics with finite optics.

Selling my Canon FD 200mm F/2.8 lens

Last edited by zzffnn on Tue Oct 03, 2017 2:22 pm, edited 1 time in total.

PostPosted: Tue Oct 03, 2017 1:39 pm 

Joined: Fri May 15, 2015 12:15 am
Posts: 2082
I think it has to do with the fact that many epi objectives have a circumferential illumination path and many of those have larger thread diameters, in order to accommodate the illumination pathway. If one thinks of that as the norm, the epi objectives that have various fixed tube lengths and utilize axial illumination, might not seem like epi objectives. Many of them are not marked as such and also many of them that did use axial illumination struggled with internal reflection problems. Moving the illumination path outside the objective, is a definite improvement with regards to contrast.
In the 1920's, Alexander Silverman, Dean of the School of Chemistry at Pittsburgh U., invented a tiny exterior vertical illuminator( about 2 1/2" across), which was fitted around a standard objective, similar to the way ring lights are used on a stereo microscope. Spencer produced these for a few years....obviously a response to the flare encountered when using a conventional vertical illuminator, through the objective.

Am I getting this correctly, georgetmacro?

PostPosted: Tue Oct 03, 2017 4:06 pm 
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Joined: Mon Nov 10, 2014 10:01 pm
Posts: 2545
You can make one of these for almost nothing.. I use one on occasion.. Works fine for epi-illumination..

https://www.instructables.com/id/LED-ri ... nd-loupes/


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