VIDEOGRAPHY THROUGH THE MICROSCOPE -

GETTING STARTED WITH BLACK AND WHITE

by Ron Neumeyer


I have been playing around with "videography" through the microscope for several years with relatively good success. This first article summarizes some of my early experiences.

Like many families we have a full size (i.e. large) consumer model VHS camera with a permanent lens. Needless to say I started with this unit mounted precariously on a tripod over the eyepiece. No luck! The best I could get was a tiny image in the centre of the screen with the macro setting. Conclusion - forget the home video camera.

Video systems for use on the microscope are solid by various dealers, so I called around and asked for some brochures. The cameras described therein did not have permanently attached lens, but like the SLR 35 mm still cameras were threaded to accept a wide variety of attachable lens systems a so-called "C-mount". Mechanical coupler devices of various forms are offered by microscope to fit the C-mount threading.

When I received the original literature the image capture device within the camera was either a tube or a "CCD" light sensitive electronic chip (the smallest being 1/3 of inch). The tube type cameras have now gone the way of the dinosaur, not only because of the much large size and weight, but also due to superior performance of the chip (no "flaring" and no decay with age, common to most tube cameras). I quickly decided that the solid state chip camera was the one for me!

The next question, black & white, or colour? As a beginner the b&w camera was attractive from a price perspective, $400 versus $1100! (In addition the b&w chips are more light sensitive then colour, a factor I thought was important at that time.) In addition the colour camera needs a colour monitor, again costing big bucks. I selected b&w.

The final consideration was image quality, in the case of b&w this meant "horizontal resolution" and is expressed by the term "lines". Although the image is captured by the camera it is made visible by the monitor TV. Furthermore, it is common to tape the image using a VCR. As with audio systems the final resolution is limited by the weakest link in the chain.

Normal consumer VCRs record and play back at around 240 lines, while high band machines ("super VHS and HI-8) produce at least 400 lines, almost a 50% increase. However, if a high band player or camera is connected to a normal TV, this resolution may not be realized as most sets less then 27 inches still produce only 250 to 300 lines (normal broadcast range of commercial TV networks). Large screen TV's on the other hand come can handle at least 600 lines. (The difference between viewing a normal and high resolution picture on such a TV is remarkable.)

At any rate after shopping around and comparing what was then on the market I selected a b&w system made by Panasonic, namely a WV-BP100 camera and basic 9 inch monitor. Both the camera and monitor produced 400 lines. The total cost for the hardware was around $650. This is sold as a security system and is widely used in Canada. Most major electronic companies offer similar systems although I liked the Panasonic best because the CCD can be moved about 15 mm to provide some very useful internal focusing. (Stay away from the package units solid in various department stores as these have permanent lens and much inferior electronics.)

I attached the camera to the microscope WITHOUT AN EYEPIECE. Why? As the chip is only 1/3 of an inch square it captures only a very, very small portion of the image projected by an eyepiece which in turn is electronically reproduced on a screen with a 9 inch diagonal dimension, effectively increasing the actual magnification by a considerable amount (e.g. 10x objective and 10x eyepiece could produce a screen magnification of more than a 1000x). This can result in bad case of empty magnification, especially when the image is taped and played on a 27 inch TV (although surprisingly enough not as bad as would be expected). Attaching a camera to a microscope with the eyepiece in place becomes something of a challenge and tends to produce rather ungainly configurations. Any dust, scratches, blemishes, etc. on the top element of the eyepiece stands out dramatically in the TV image. An additional Finally because of the extreme magnification following a small ciliate around while watching the monitor becomes a test of ones dexterity and patience. Ergo - forget the eyepiece!

I had a machinist cut C-mount threading into the end of a spare eyepiece tube, screwed it to the camera and slipped the complete assembly into tube of the microscope. This arrangement, while simple to execute has one relatively minor flaw, the CCD is not in the "ideal" location, namely at the level of the primary image formed by the objective. However, with the BP-100 this was only 25 mm, not a big deal and only minor adjustment from visual focus was needed.

When I first set up and turned on the system I was disappointed in the contrast of the image which appeared somewhat washed out. However after playing around with filters (in a sense b&w is much like photography in respect to filters) I found that a dark green filter vastly improved contrast. The security monitor also allows for more adjustment of contrast and brightness then a conventional TV.

Comments to the author sent via our contacts page quoting page url plus : ('rneumeyer','')">Ron Neumeyer.

 

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