Adapting a Canon 300D (Digital Rebel) Camera for Photomicrography Through a LOMO Multiscope Microscope

 
Text and photography copyright Ken Vernon 2005. All rights reserved.
 
 
 
 
 
 

When I received the Lomo Multiscope it came complete with a trinocular photo-tube and a spacer attached. I attached the 300D to the photo-tube using a Canon EOS T Mount made by Celestron. For my first attempts at photomicrography with this setup I used a medical specimen slide and focused the microscope through the camera's viewfinder. The Canon 300D cannot be equipped with a clear focussing screen so it is not exactly easy to see the specimen and focusing needs care. The camera was set to aperture priority exposure mode to allow the camera to determine the proper exposure and I used a Canon infra red remote to fire the shutter.

   The initial results were disappointing; the images were blurred. I guessed that this was due to vibrations from mirror slap. I then changed to shutter priority exposure mode and performed a series of test exposures, increasing the shutter speed for each successive exposure. Sharpness improved gradually and, at 1/400 sec., I obtained a sharp exposure. At this shutter speed the resulting image was almost black and needed the use of large amounts of "Levels" in Photoshop to see the image. The image was sharp but otherwise of extremely poor quality due to the large amount of "Levels" applied.

 

The next step was to separate the camera from the microscope so that mirror slap vibrations had no effect on image sharpness. I bought an old B&W enlarger, stripped all the lens assembly etc. away leaving just the base and a very stable metal pole to which was attached the cast alloy illumination box - this box was very rigid. I then attached to this box (epoxy glued) a solid macro-focusing rail which had been engineered from a macro-bellows. The camera was mounted on the rail and placed in position above the microscope's trinocular port. The focussing rail allowed precise positioning of the camera above the relay lens so that I could obtain parfocality of the camera and the eyepieces. I was also able to use mirror lockup (thanks to hacked 300D software) and this solved the problem of mirror-slap vibrations. A black plastic sheet skirt was attached to the T mount and held in place on the photo-tube with an elastic band to keep any ambient light from entering the tube.

   Unfortunately, another unforeseen problem occurred. I found that each morning the parfocality was out and the first images were blurred. I was advised that it was possible that because the Lomo turret assembly and photo-tube actually moved up and down when changing focus on the microscope this could affect the critical distance of the camera's sensor and the relay tube. At about the same time I had received a very good flash set-up designed and built by Charles Krebs. Charles suggested that I go back to having the camera set directly on the photo-tube. He said that the flash had a minimum duration of 1/1000th sec and this would overcome any vibrations produced by mirror slap. I did asuggested and Charles was right! I achieved parfocality of eyepieces and camera by using extra spacers on the phototube (I had been able to accurately measure the distance between the camera and the photo tube when I had it attached to the enlarger stand). I now had a very good set up in which the mirror slap vibration caused by the 300D was fully overcome.

 
Without electronic flash.
 
With electronic flash.
Editor's note: It may be difficult to see differences in sharpness when image files are reduced to fit on a web page. The original, full-sized files demonstrate a decided sharpness difference between these images, the electronic flash image being significantly sharper...TLW

 

That, however, was not the end. The previous problem of having the parfocality upset overnight returned. Each morning I would fiddle about for 10 mins or so and would finally get the parfocality right again, but this happened every morning. I wondered if the cause might be there some movement in the microscope itself during the time it was getting warm from the quite hot lamp housing in the base of the microscope. For three consecutive mornings I checked and the parfocality was out overnight, as previously, but I simply left the microscope switched on for 20 mins and would return to find parfocality was restored!

I have included photographs of the Charles Krebs flash set-up with the microscope...

Editor's Note: The flash used in this setup is a Vivitar 283 with a custom-designed output control unit designed by Charles Krebs. The flash burst is directed to the sub-stage condenser by a plane piece of glass held 45° over the field condenser...TLW

  
 

 

About the Author

Born in Yorkshire England in 1934. I spent ten years in the British Merchant Marine and a further 10 years in Electronic Intelligence Gathering (a Spy! LOL) and the rest of my working life in communications. I came to live in New Zealand in 1967 and found it to be the most beautiful country on earth! I first became interested in Microscopy 20-25 years ago but it didn't last long. I'm pleased that I found my way back to it, not only a very interesting hobby but also a joy to belong to this extraordinary group of very fine people.
 
 
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