Canon A70 Microscope Adapter

by Howard Webb (St. Louis, MO, USA)

Introduction

I finally got a new digital camera to replace my Kodak DC3200.  While the factors of the decision were not just microscopy, it was a definite consideration.  The features I wanted were:

The Canon A70 met all these needs.  In fact, most of the Canon line of cameras are similar; and what I say about the A70 likely applies to the other models as well.  Price kept me down to the 3 megapixel range; for more money, I could have had the same basic camera with more pixels (Canon A80).
One of the unique features of the Canon camera is its lens adapter.  There is a tele-extender lens, and wide angle lens available that screw into the front of the lens adapter via a standard 52mm thread. The lens adapter attaches to the camera via a 'bayonet' mount, and extends forward enough so anything screwed to it clears the camera lens.   This adapter opens up the possibilities for all sorts of other mountings (of my own making).

The camera mount

Microscope with cameraI asked at my local camera store what they had in the way of 52 mm rings.  I expected that I would have to take a 52mm filter, and smash out the glass to get a ring.  It turns out they had a drawer of used adapater rings, and gave me a 52/58mm ring for almost nothing.
Building the rest of the adapter was fairly simple.  I need a 'plate' to hold the camera just off of the microscope objective, and a way to securely hold the camera in place, centered over the objective.
The plate was made from a scrap piece of 4" PVC pipe.  I cut the pipe in half (vertically) then dropped a piece in boiling water.  The heat allowed me to flatten the PVC into a sheet.  With a compass, I drew circles on the PVC sheet; for the outer diameter, inner opening, and at 1.25 inch as a gluing guide for the pipe.  The inner hole is slightly larger than the objective lens, yet smaller than the objective housing.  This allows the plate to sit on top of the lens, without obstructing any of the light path.
1.25 inch PVC was the smallest pipe which will fit over the objective and the microscope barrel, a piece of this holds the camera to the microscope barrel.
I assembled these three pieces using epoxy cement, taking care to not get any cement in the threads of the ring.  I painted the top of the plate black to avoid any stray light reflection.
I drilled and tapped three 1/4 x 20 holes around the base of the pipe for nylon bolts (this is the same size as a standard camera tripod mount).  The nylon does not scratch the microscope, yet holds the mount solidly to the microscope.  Initially I had planned to shim the inside of the pipe to center the objective lens, but I was unable to find anything that fit snugly around the lens, yet would smoothly slide into place.  I ended up adding three more bolts to the top of the pipe, which has proven to be a simple but effective solution for centering.

Use

Adapter and mountInitially the mount was a frustration.  I thought I was getting a good picture when looking at the LED display on the back of the camera; yet, when I downloaded the image and looked at the enlarged version, I usually discovered it was out of focus.
Initially I had not wanted to use the remote capture software, which came bundled with the camera. I thought it would be too much work; not only moving the microscope up to the computer desk, but the light rheostat and other stuff.  It turned out the program exposure setting of the Canon automatically adjusted to the full light intensity, hence the rheostat was not necessary.  The remote capture actually reduced the work.
The software proved to have a number of advantages.  First, it provides a good size screen image for sharp focusing of the microscope, it also avoids the standard digital camera delay between the time the shutter is pressed and when the image is captured.  Triggering the 'shutter' via the mouse also eliminates any fingers jiggling the camera.
I am now no longer touching the camera, it is just a computer adapter for the microscope.  The set-up allows me to concentrate on the subject, adjusting the focus, and clicking away as many images as I want.

Negatives

Larger images and better detail does have its down side.  For web publishing it is good to keep the images small (about 50-80K).  A  2048 X 1538 image (high quality) can easily run 1.5 to 2 meg in size - a long download.  Fortunately, dark field images have a lot of the same color and average only 600k (still a large file).  The zoom lens also avoids vignetting, so there is less image to crop off.  Every speck of dirt and air bubble also show in the image, making a clean slide becomes more critical.  Then again, these are the very challenges that interested us in photomicroscopy.

Images

The following subjects were quick grabs from my daphnia cultures and aquariums.  The image on the left is a reduced version of the full frame image (15%).  The image on the right is a cropped, full size portion.  Magnification is the microscope lens combination; the camera was likely zoomed to 3x.

Daphnia - small image
Daphnia pulex - 40x


Daphnia - full pixel
Daphnia pulex - 100x

Daphnia Head - small
Daphnia pulex - 100x

Daphnia head - full pixel

Bladderwort tendril - small image
Bladderwort tendril - 100x

Bladderwort - full pixel

Rotifer - small image
Rotifer (sp?) 400x
A live rotifer is a real challenge to get while moving!

Rotifer - full pixel


Technical Details

Microscope: Bauch & Lomb monocular, 10x ocular, 4x, 10x and 40x objectives.

Camera: Canon A70.  Via the remote capture software, turn off auto-focus and auto-focus light.  All other settings were left at default (I will learn to play with them another time).

Software: Photoshop Elements

Comments to the author Howard Webb are welcomed.


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Published in the April 2004 edition of Micscape Magazine.

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