#58
Post
by PeteM » Wed Dec 22, 2021 4:19 am
Curious about the Wild M7a, today I plundered my budget and bought four of them. I'm pleased with the quality of this scope - and thought a report might be useful to others. There seems to be much more information about other Wild M series (M3, M3x, M3z, M5, M8 etc.) scopes available on various forums.
These were apparently last serviced decades ago, yet all but one came to me still aligned and with a smooth and parfocal zoom function. Perhaps a testament to their design and build quality.
One of the four had a sticky set of zoom elements. It would hesitate a bit after turning the zoom ring for the springs inside to pull the zoom elements parfocal. Opening it up was simple - three screws. Just taking a foam swab with a bit of oil and cleaning off the some sticky grease on the guide bars restored the zoom function.
The inside of these is beautifully precise and functional. For example, the zoom cam is machined out of brass and the balanced cam followers are ball bearings. I'd be surprised if any new scope under $10K is better built mechanically. The bottom line being, I think one of these could outlast a few Chinese zoom scopes with plastic gears and guides.
The zoom on these goes from 6x to 31x with 10x eyepieces. The 1x objective (fixed by three screws) is apparently plan achromat. It has better field flatness than a Wild M3 or a Nikon SMZ-10 as examples. I suspect that the difference between the M7 and M7a is a flatter-field objective as was done with the Nikon SMZ-10a superseding the otherwise excellent SMZ-10? Someone like jfresto or Scarodactyl might know?
A 6x low magnification is quite useful - much better to my mind than a scope whose lowest magnfication is 10x. 31x is more than most people need in a stereo microscope since 40x from a compound microscope might be the next step up. I tested both the Wild/Leica .5x and 2x clamp-on auxiliary lenses and they work fine. At the high end there is still useful magnification. The .5x reduction lens might be perfect for someone building a model or doing circuit board work. So a range from 3x to 62x is feasible.
The one minor puzzle in quickly testing was that the zoom on one of these (the previously balky one) tended to drift down on its own - with springs inside providing tension. Turns out there's a thumbscrew on the side to stiffen this up or even lock the zoom to a single focus. It could be -- and someone might inform me -- that greasing the large helicoid with a damping grease might also have been an OEM spec?
Comparing this scope to something like a Bauch & Lomb StereoZoom 4, the Wild M7a it is better made, avoids the use of hard-to-clean first surface mirrors, has a wider field of view, a slightly wider zoom range, and (to my eye) a better image. It should also be easier to maintain over the years. The B&L SZ4 is a very decent scope. This one is significantly better IMO.
Comparing this scope to something like the next step up Wild M8, it appears to accept the same heads, photo heads, irises etc. - but not the screw-in objectives. The M8 will have a still-wider zoom ratio, but also likely a significantly higher price tag. Mechanically, the M7a probably cost more than the M8 to build.
Comparing it to something like an Olympus SZ-4045, it seems optically about the same, but with a better build quality.
I also tested this with Chinese 10x/22 eyepieces machined to reach further into the tubes (beside the Wild Leica 10x/21b). They work fine, with an extra 1mm field of view without vignetting.
Bottom line - a very nice scope if you find one affordably priced. I'd prefer one of these in good shape to the $500 or so new Chinese zoom scopes I've seen so far.