Stereo zoom microscope magnification question

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Chris_Moody
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Stereo zoom microscope magnification question

Post by Chris_Moody »

Hello all

Please forgive this basic question, but I'm having difficulty in finding an answer due to my lack of experience in both microscopy and photography.

Basically I have a cheap stereo-zoom microscope with a magnification range of 7.5 - 90x. I have connected a Canon 40D to the trinocular tube on the scope.

I don't know whether its due to the cheapness of the scope, or the way low-power stereo scopes work, but the magnification is fixed. By this I mean the magnification adjustment seems to work as a coarse focus adjuster, with the normal focus knob acting as a slightly more fine focus.

I am left wondering what magnification the photos are at, it'd be easier if the camera was attached to the trinocular tube with a 10x eyepiece, as it seems then the magnification adjuster works and zooms in/out, and I could work out the magnification based upon the value on the adjuster. I am guessing as it is the magnification is based upon the base magnification of the fixed objective?
Last edited by Chris_Moody on Sat Aug 28, 2010 8:21 am, edited 1 time in total.

Charles Krebs
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Post by Charles Krebs »

I have connected a Canon 40D to the trinocular tube on the scope.
We'll need a lot more info on how this was done to really answer your questions.
I have a cheap stereo-zoom microscope with a magnification range of 7.5 - 90x.
That's quite a long range for an inexpensive stereo. Is this with 10X eyepieces? Is some of this this range achieved by changing to different power eyepieces?

You can't just attach a camera to the trinocular tube without some consideration where the actual image that is formed by the microscope optics is located. Then you can approach it a few different ways...

1) direct projection (very often not possible because of physical constraints)

2) via a projection eyepiece in the trinocular tube (no lens on camera)

2) with a "regular" eyepiece in the trinocular tube and a suitable lens on the camera body ("afocal method").

With all these methods the positioning and spacing of the components its pretty important.

Chris_Moody
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Joined: Wed Aug 11, 2010 8:51 am
Location: Bournemouth, UK
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Post by Chris_Moody »

Hi

I was actually just coming on to delete the thread as I realised how much of a numpty I was being yesterday. I must have been a little confused yesterday, as the zoom knob does in fact adjust the zoom, I was getting thrown out by the fact that the focus deteriorated much more than when using the binocular eyepieces, and that I'd had a little bit of a drink earlier!

When I say cheap, it cost £500, so it's not "cheap" per se, but compared to laboratory grade equipment I'd say it is!

Here's a picture of the set-up.


Image
Microscope setup by Chris_Moody, on Flickr

The microscope came from radical instruments in India, and the information is a bit vague on the specific specifications.

As far as I understand it, the camera is connected via a t-mount directly to the Trinoc tube. This gives the best picture it seems. I also accidentally got sent a wrong diameter t-adaptor tube, but it is just right to sit on top of a 10x eyepiece for the tube, so I have the option of directly connecting it to the tube (via a 22mm adapter), or putting the eyepiece inbetween using a different adapter. However the eyepiece degrades quality a fair bit around the edges, so I think its best not to use this.

Here's one of the critters I was photographing yesterday, no eyepiece. I am busy trying to work my way through a universities entomological collection to get them on a taxonomic directory! The photo below is made up of 3 stacks processed in Helicon focus and then merged in Photoshop.

Image
Chlaenius nigricornis by Chris_Moody, on Flickr

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