Trinocular Microscope to DSLR Interface

Digital Microphotography


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I have a Variscope Series 824 Trinocular Stereo Zoom Microscope. I am failing to achieve reasonable picture quality from the DSLR attachments sold to me as the correct products for this purpose. In this status this project remained from November 2008 until January 2012. The scope is great as a regular microscope but it was (and still is) non-functional as a photographic tool. In January of 2012, I am trying again...

Variscope Series 824Variscope 824 Trinocular port, 27mm(?)

The microscope even though a relatively inexpensive model, it does provide crystal clear normal eyepiece viewing. When viewing by eye through the trinocular port, using the 1X C-Mount adapter tube, the silver adapter tube and the photoeyepiece, the image is also crystal clear (to the eye).

 Trinocular T-Mount AdapterTrinocular T-Mount AdapterTrinocular T-Mount Adapter

When placing my DSLR, a Nikon D300, on the trinocular port with the 1X C-Mount adapter tube, the silver adapter tube, the photoeyepiece, the T-Mount adapter and the appropriate T-Mount ring for Nikon cameras...
  There are two points where optical path length adjustment is possible:
      Below the photoeyepiece (between the microscope optics and the photoeyepiece)
      Above the photoeyepiece (between the photoeyepiece and the camera sensor)

      When changing the optical length above the photoeyepiece, it seems that the magnification is changed and little or no focus correction occurs.
      When changing the optical length below the photoeyepiece, the focus adjustment occurs and little or no magnification change occurs.

At no point of adjustment of these two optical lengths is it possible to achieve true, crisp image focus. It is possible to achieve a focus that is somewhat close to correct but it is NOT a crisp, clear image. To clarify, with this configuration, the photoeyepiece is projecting the image directly onto the camera sensor.

 Trinocular T-Mount/Macro Lens AdapterTrinocular T-Mount/Macro Lens Adapter

Alternately, I have tried inserting a Nikon lens in the path to insure a valid image on the camera sensor. For this, I used a Nikkor 60mm micro lens. I have an old Nikon ‘E’ adapter that has an internal 42mm female thread that provides an adapter from 42mm female thread to Nikon female Nikon lens mount. I have an old BR2 adapter ring that has a Nikon male camera mount to a 52mm male thread. Next is a 52mm female thread to 62mm male thread adapter ring that finally screws into the 62mm female filter threads on the 60mm micro lens. (The internal 42mm female thread on the ‘E’ adapter is presumably a 1mm pitch. The external 42mm male thread on the T-Mount tube is .75mm pitch. The pitch of these two pieces is different but I am able to screw them together about 1 turns to provide a good physical connection without damaging the threads.)

This assembly goes above the trinocular port, 1X C-Mount adapter tube, silver tube, photoeyepiece assembly. The same two optical path length adjustments are available. While this seems promising, I am able to adjust it to ‘approaching’ correct focus but I run out of adjustment travel before achieving true focus. The assembly seems just a wee bit too long. I am thinking that the length of the ‘E’ plus BR2 ring is about ” and from hand holding the pieces in position, it seems that I need to get about 3/8” closer. I am planning to get a 42mm female T-Mount thread to 52mm male filter thread adapter to replace the ‘E’/BR2 pair to test this idea. This should shorten the assembly by more than ” and reduce the overall assembly minimum length to less than what hand holding seems to indicate is the proper length. After about 2 hours of Internet searching, it seems that I can only find this adapter in England or Australia, not in the US. Many web sites fail to provide specifications for their adapter ring products so it is impossible to tell if what they are selling is what I am trying to find. Alternately, I could cut one of the tubes to make the path shorter. I will order and await the adapter from England. I prefer to not cut any pieces as I am really just guessing at what needs to be done.

 

I am frustrated that I purchased products that were supposed to provide the proper interface between the trinocular microscope port and a DSLR camera. When I test the products, it does provide an adequate physically interface but there is something very wrong with the optical interface. This optical interface will only produce low quality images. Both the microscope and the camera are capable of much better image quality.

 

(I am also a little uncomfortable with the not sealed adapter tube connections that fail to provide complete dust protection to the camera's sensor cavity. I am inclined to instead use the Nikkor 60mm micro lens and have a better dust seal for the high quality image solution.)

 


All images copyright Mike Baker
 


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