Basic questions on SMZ-10 configuration

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Or, move the prism and open the shutter electrically

Post by genera »

I’ve found, at least on my AFX unit, that I can drive the prism assembly out of the optical path by using the AFX’s internal motor. I opened the unit and traced the motors wires through the internal connectors and PC boards to pins on the external rectangular connector. This was pretty straight forward since there aren’t any relays or other electronic components in the motor’s path. To move the prism you must apply voltage from a battery or power supply (I used a 9v battery), +V to pin 1 and –V to pin 8. With voltage applied the motor will rotate moving the prism assy in and out of the optical path. The motor rotates slowly enough that you can pull one of the battery leads from the connector when the prism is in the desired position. It will stay in that position until you reapply voltage. (If 9v moves it too fast use a lower voltage).

After that I decided to see what I could do about the shutter. As it turns out, these shutters latch in either the open or closed position depending on the polarity of the voltage last applied. By momentarily applying power from the same 9V battery to pins 10 and 11 on the external connector you can open or close the shutter and it will stay in that position until you apply a pulse of the opposite polarity (by swaping the battery leads). Don’t leave the battery in place longer than needed. Very brief contact is all that’s required.

In most cases these actions need only be done one time. If you find that you do need to move the prism or open/close the shutter frequently it shouldn’t be difficult to rig a small box with the necessary controls and a battery.

Pin numbers are marked on the external connector.


One mechanical modification is required whether you adapt your AFX/UFX as Nathan describes in his article or as I describe above. The chromed ring around the camera mounting flange at the top of the camera mounting adapter (adapter “A” in Nikon literature) interferes with the lens flange on Nikon DSLRs and must be removed. See Nathan's article.

While you have your tools out I suggest that you consider two additional modifications.

There are three or four electrical contacts on the bottom of adapter A as well as a removable indexing pin. These contacts and pins mate with contacts or a slot on top of the AFX unit and have the effect of forcing a landscape orientation on the camera. If you remove the adapter’s baffles and then remove these electrical contacts plus the locating pin you’ll be able to rotate (for better composition) your camera from landscape to portrait orientation or to any other position around a full circle. The camera will be securely held in the desired position by the large threaded ring on the bottom of adapter A.

You could do this rotation at the subject (though lighting or polarization might be affected) or at another joint between adapter sections but there’s a large bearing surface here and it locks well so, if you want rotation, this seems like a logical place.

If you implement the above change and before reinstalling the baffles notice that there’s a pin protruding about 8mm above the camera mounting flange of adapter A into the area where the camera body will be. This pin was originally used to open a secondary shutter on the film box so that you could safely remove or install the box with film inside. It serves no useful purpose on a DSLR. This pin is out of the line of sight so not a problem in that sense but I worry that it might physically interfere with the electronics or other features on a DSLR body. I’ve not looked at this very closely nor have I seen any reports of a problem but I’ve taken the precaution of breaking this pin off “just in case”. In the light colored adapters this pin is part of the main aluminum casting and is easily removed by twisting it with a pair of pliers. On the older black adapters (mostly from PFX or early AFX) the pin is screwed in and may be removed and set aside for later use.

Be sure to block any openings you’re not using, such as pull rod holes or the AFX viewfinder mount, with opaque material.

With the SMZ-10 parfocality is adjusted in the photo port by raising or lowering the projection lens. You do need to replace the standard chrome adapter tube at the bottom for the AFX unit with an adapter “SM”, seen in Nathan’s first photo. This is necessary because the top of the projection lens extends beyond the top of the photo port and will interfere with the bottom of the AFX.

Some measured lengths for reference:

Bottom of AFX / UFX to F mount flange on adapter A: 120.7mm (virtually the same as a Diagnostic Instruments PA1-12A).

Adapter SM adds 37.8mm offset.

Overall height is 158.5mm from the F mount flange on adapter A to the bottom of adapter SM.

Other microscopes, including the SMZ-10A, have different adapter requirements.

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