Advice needed attaching Canon Mark II to Oly BHS Trinocular

[Joe Sukenick]

First, the amount of help available on these forums along with the images posted is incredible! Thank you all. The posts when OzRay was choosing a microscope read like a guide to buying the right gear and was invaluable to me when choosing to suit my needs.

While I am waiting for my Olympus BH2 to arrive, I am unsure of the preferred method and NFK magnification to attach my Canon 5D Mark II to the trinocular of the scope and have a few questions that I could not find answered in the forums.

I would like it to be parfocally adjusted and directly connected in a secure non-slip manner since I will be capturing using "live-view".

What is the preferred NFK magnification for the full frame Mark II full frame sensor with this BH2?

Is there an off-the-shelf adapter to connect the Canon Mark II camera to the trinocular tube or is a custom approach needed?

Joe Sukenick

[Planapo]

Joe, welcome aboard!

I am dealing with similar questions, with an Oly BHS standing next to me, though mine is still wrapped up safely in a box due to other ongoing work.

As far as I know, for the 35 mm film SLR Olympus OM camera bodies, the NFK 2.5x was used for best coverage. So I presume for your full frame body this should be the appropriate projective.

Regarding a way of adaptation: For their 35 mm film SLRs Olympus provided a so called "Photomicroadapter L" with an OM bayonet mount. My BHS came with this Photomicroadapter fitted to the photo port of the trinocular tube.

Now together with one of these widely available adapter rings to fit OM bayonet mount lenses to Canon EOS bodies, I would expect that one can couple EOS bodies to this OM Photomicroadapter. That's the way I have in mind, if I will use Live view where mechanical decoupling of camera and scope to prevent vibration issues seems not necessary anymore.

My five cents, let's see what our more experienced photomicrographers think.

--Betty

[g4lab]

At my other favorite forum Gemology Online dot com people are always wanting to stick digicams onto their stereo microscopes. They always ask me what to buy. I always say I can't tell because they rarely know their chip size and many of the other required factors.

I ran across this Java Applet at microscopy u which is a good one.
They need to update it to reflect full size 35mm DSLR chips and perhaps add a version for point and shoots like the coolpix.


Here however is a good applet showing the difficulty in predicting the match between a digital camera and a microscope. You can see that the lower the magnification the more and smaller pixels you need to have. This is why putting cameras on stereos is harder than putting them onto regular higher mag compound scopes. The only problem with this applet is it stops at the so called One Inch chip size. Most DSLRs have much bigger chips for a long time.

[Joe Sukenick]

Betty,
Thank you for the welcome. I suspected it might be either the 2.5X or 3.3X. After checking g4lab's link, it seems it may be both.

g4lab,
That applet pointed out some of the missing pieces in my formula when trying to think this through. As it is with most photography questions, the usual answer almost always starts out with "It depends on....".

I am already sensing a very strong similarity between amateur micrography and the definition of having a boat as a hobby. BOAT - A hole in the water into which you throw all your money."

Joe Sukenick

[g4lab]

I am already sensing a very strong similarity between amateur micrography and the definition of having a boat as a hobby. BOAT - A hole in the water into which you throw all your money."

Or the racers question. "How fast ya wanna go?? How much money ya got."

At least a microscope won't sink!

[Charles Krebs]

Joe,

As far as magnification goes check out this link for some useful info:
http://krebsmicro.com/relayDSLR/relay_micro.xls

If you have the eyepieces most commonly used (WHK 10X) you will see a field number (FN) of 20mm. The spreadsheet will show you the FN that will be recorded with various relay magnifications on different formats. For 24x36mm a 2.5X was the most widely used, and this records a FN of 17.3mm across the diagonal. A 3.3X was also used with this format, and it gives a FN of 13.1mm.

The diagram below give an idea of what we're talking about. The whilte circle represents a view seen through 10X eyepieces with a FN of 20mm. The red rectangle would then represent the field recorded on a 24x36mm sensor using a 2.5X NFK photo-eyepiece... 17.3mm diagonally. The blue rectangle represents a 3.3X NFK.



As far as attaching the camera. By far the easiest would be to use the Olympus “Photomicro Adapter L” that Betty mentioned. This is basically a tube that attaches to the dovetail at the top of the trinocular head and has the Olympus OM mount on the camera end. An Olympus OM to Canon EOS adapter is readily obtained on ebay for about $15.00. You can see the Olympus L adapter here:

http://www.alanwood.net/photography/oly ... ter-l.html

If you have the BH2-TR30 trinocular head this adapter will clamp directly to the trinocular tube dovetail. (If you have an older trinocular head…. BH or BHA with a smooth 25mm tube, you will need an adapter also seen on that web page).

Diagnostic Instruments makes an adapter, PA1-10A, that also is used in a similar manner. It has a T-mount camera coupling. So if you can't track down an Olympus Photomicro L, that's a good way to go as well. (Their equipment is well made and it will probably cost more than the Olympus one. But at least it should be readily available while it may take a while to find the Oly L adapter).

To make the eye view and camera focus absolutely “parfocal” it would be ideal to have some fine adjustment in that L adapter. But you don’t. If the focus is close enough (I’ve never tried it) it might be possible to first achieve accurate focus in the camera --- easy to do with “live view”. Then, without touching the focus knobs, adjust the eyepieces in their tubes until the view through them is simultaneously in focus. The left eyepiece on the BH2-TR30 is adjustable, the right is not, so you would likely need to shim or tape the right eyepiece at the appropriate height. Ideally you would not want to “lift” the right eyepiece in it’s tube, as this then increases the tube length, but a very small amount will have no real consequence. (It can become an issue with “high/dry” objectives like a 40/0.95). If all you need is a fraction of a mm more in the camera height it might be possible to put some thin shim material between the trinocular and the base of the L adapter.

[Charles Krebs]

Gene,

You can see that the lower the magnification the more and smaller pixels you need to have. This is why putting cameras on stereos is harder than putting them onto regular higher mag compound scopes. The only problem with this applet is it stops at the so called One Inch chip size. Most DSLRs have much bigger chips for a long time.

The spreadsheet listed above includes formats through 35mm. It's quite revealing to see how the pixel requirement change at the relay magnifications change. Since the NA of most stereos is pretty low (- 0.10), and the sensors on the DSLR's are larger than shown on the Nikon U site, nearly all DSLRs you come across can easily "handle" a stereo scope. But yes... if you've got the latest, hottest research stereo (like an Olympus MVX with a 0.25 Plan Apo) you better have some pixels! (But if you have that scope you're probably not putting a DSLR on top of it )

[Joe Sukenick]

Charles,

The variables involved are now becoming even more clear with your example. This certainly helps.

Since I do not have the BH2 yet, the trinocular head type is unknown to me. Once I get familiar with the microscope I will then add the hardware for the camera.

Joe Sukenick

[g4lab]

Charles,
Thank you. I had looked at your spread sheet a long while ago at which time my gemology friends were not hounding me but every one seems to have gotten a new scope and or camera lately.

Gene