Unorthodox photomicrography

The most convenient method of attaching a camera to a microscope is via the central tube of a trinocular instrument. This allows viewing of specimens via the eyepieces or switching the image to the camera for photography. I chose a different approach, however, because I regard a microscope as an accessory for my camera rather than vice versa. Having no need to view specimens via the eyepieces, I removed the upper part of the microscope and replaced it with two in line tubes on which to mount a camera. Using the 4x and 10x finite microscope lenses I had already been using for extreme macro work meant that I did not require a photo lens. I do have a polarizing filter fitted in the tubes, though.

When buying a microscope, I had the choice between a new, modern instrument or an older, possibly better quality, used instrument. I chose the latter: an Olympus BHB. I am really pleased with my choice because, although the microscope had been well used before it came to me, the focusing mechanism is still faultless despite my taking thousands of automated images for stacking.

When it came to modifying my microscope for taking stacks of images, I first added a baseboard to which I could fix accessories instead of drilling into the microscope body. This means that I can return the instrument to its original condition and can move the accessories to a duplicate instrument if the first one fails. I bought a stepper motor to plug into my Stackshot control unit and rotate the fine focus control on the microscope. I used an intermediate miniature pulley and belt system because I was unsure what would be the optimum gear ratio. As it happens, direct drive ratio would have been OK. Because I was concerned about sideways stress on the focus control, I connected to it via a ‘cup’ with a soft lining and was careful to make sure the connection was properly aligned. The cup only needs a light touch for sufficient grip.

Stepper motor and pulley system

The original tungsten lighting on my microscope was sufficient for bright field illumination but was inadequate for dark field, especially when filtration was used. I replaced the lighting with a new LED system. Dark field illumination can be achieved by adding a ‘spider’ light stop to the condenser. This stops the central light rays, only allowing the peripheral rays to pass. The original condenser gave somewhat uneven lighting when used with a 4x lens for dark field work and so I made up a simple replacement version with a built-in stop and double-convex lens.

Home built dark field condenser

When photographing birefringent crystals, I add a second polarizing filter below the specimen and rotate this filter to bring out colours in the specimen. This technique can also be used on biological specimens. Further control of the colours and which parts of the specimen they affect can be obtained by adding wave plate filters. I bought sheets of filter material, cut it into discs and turned holders for it. The holders fit into each other and so can be stacked.

Crystals with 'crossed' polarizing filters

I use a Canon EOS 7D for taking images with my microscope. The camera has live view with EFSC to limit camera shake and was fairly inexpensive on the second hand market.

Some of the photomicrographs my wife and I have entered in the Nikon Small World Competition can be seen at:

https://www.nikonsmallworld.com/people/anne-algar

https://www.nikonsmallworld.com/people/christopher-algar

I should point out that my knowledge of microscopy is very limited - I just learned enough to set up and use my microscope.