MicrobeHunter.com Microscopy Forum

First, thanks for any help. I have a new-to-me Wild M7A that appears to be in very good condition. I immediately have 3 questions. First, can the interpupillary distance be adjusted? Second, it has a 404891photoube with a dirty lens down in the bottom - how do I clean it? Third, it has Carl Zeiss Pl 16x/16 occulars which I may want to replace at times with lower powered occulars, say 5x - what will fit? Thanks

He interocular distance is easy, just adjust the ocular tubes with your hands (gently, of course).
The trinocular port can be disassembled, usually by unscrewing bolts from the bottom.
5x oculars are probably not going to be viable (wild made some at some point but they were likely meant for photographic use), but you can use ultrawide 10x eyepieces.
Congrats, the M7 is a superb stereo.

+1 to all that above. It's a fine stereo microscope.

Wild 10x/21 eyepieces can be made parfocal throughout the zoom range. Generic 10x/22 or so eyepieces will work nicely, but may need to fit a bit deeper into the tube to be parfocal. Doing so requires enough metal in the eyepiece shroud to turn them down so they sit 3mm or so deeper.

A pair of generic 10X/22 eyepieces I tried had too limited of a diopter adjustment to reach Wild's unusually deep intermediate image.

On the other hand a pair of Zeiss W-PL 10X/23 oculars (and I would guess the Asian copies of them) are just parfocal when contracted to their limits. I refuse to shorten the eyepiece tubes as I think Wild Microscopes should be protected historical technical monuments.

Here's my workaround:

With 3d printed clamps you can hold those chepa Chinese ultrawides right on the ocular and get parfocal viewing. I need to put the file up somewhere.

Here's my approach. It's the eyepiece which is turned down to seat a bit deeper. Should be noted that not all of the generic 10x/22 eyepieces have enough "meat" to allow this. For those that do, the view is quite good and a bit wider than the Wild/Leica originals. An o-ring of various diameters can be used for slight diopter changes.
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Note that thr normal heads will cover 26.5mm fn eyepieces but low profile and ergo heads will not.

Scarodactyl wrote: ↑

Fri Sep 23, 2022 11:00 pm

Note that thr normal heads will cover 26.5mm fn eyepieces but low profile and ergo heads will not.

Would you know if the vignetting is from before the projection of the infinity optical paths or after? I ask because I have extended the i.o. path on a microscope, so that inserting the 30° ergo wedge would be a problem, and am considering a low angle head.

I think it happens in the prisms in the head after it has hit the tube lenses. I'll admit I'm unclear what you mean by extending the infinity path though, it should be infinite until it hits the lenses in the bottom of the head and probably through the entirety of the ergo wedge.

Thank you for your reply. I am sorry my posts the last few months have not been as clear as they perhaps should be from lack of sleep. (I have someone working on that.)

I may be trying to insert one too many optical units between the objective and eyepieces. By I doing so, I risk lengthening the infinity optical paths enough to vignette near the eyepieces. I have some things to try before I consider what a surgical/ergo head might add.

Oh I see. I suspect it wouldn't make things worse, it just caps the maximum coverage at just barely over 21mm. After all they do/did offer those bellows style ergo attachments for leica stereos which could add a ton of extension on their own.

Re. cleaning the 404891 - I got some CleanTip swabs from Texwipe - nr. TX761 - and some drug-store variety 70% Isopropanol and just slowly went over the glass surface that is visible in the bottom of the tube, looking from above. I did not remove the adapter, and I didn't take anything apart. I alternated using a damp (with alcohol) swab, and a dry one to pick up the residue, and it took about 5 cycles (10 swabs) to get it clean. I don't know exactly what optical component I'm looking at/cleaning - it was not the prism which sits below. There was what seemed like a substantial layer of crud on the surface, which is now gone. I have before-and-after images that surprised me - there was not an obvious difference in quality, i.e. even with a dirty adapter, this things gives great images.

That's just a mirror I believe, open to the elements when no camera is inserted and something of a dust magnet so unsurprisingly often quite dirty. Fortunately the grime is out of focus so it kostly affects contrast.

I second the recommendation for 10x widefield as being the most useful magnification. However, it's not generally a good plan to use any old 10x eps from a biological compound scope, as these all sit 4mm too high for parfocal zooming to be possible. I tried it with Zeiss Pl 10x/25, with the dioptre adjustment as far down as it would go, and I still couldn't get there. Either one should take 4mm off the eyetubes (eek... I wouldn't do this unless I had a spare bino head) or turn 4mm off the eyepiece body as long as there's enough metal for that to be possible, as PeteM noted above.

The best solution and one which allows parfocal zooming is a Wild or Leica 10x/21, which are of course what were originally fitted and have the intermediate image plane in the right place.

Peter

A pair of Leica 10445111 10x/21B oculars, weirdly bundled with a microscope lacking 30mm eye tubes,
seem to have no more correction than similar Nikon or Chinese eyepieces, at least to my aging eyes.
Presumably because of their idiosyncratic clamps, they are not quite parfocal in a Nikon UW head..

The 445111 have no compensation for LCA and so are optically comparable with Nikon 10x/25 or 26.5, Zeiss Pl 10x/25 and in fact most 10x/25 fitted to infinity scopes, all of which apart from, I think, Leica, have any necessary LCA compensation done in the tube lens. The magnificent Leica HC Plan S 10x/25 probably have a touch of compensation, but I don't notice it in viewing and anyway, for me it's the photo setup that has to be perfect as any defects there are painfully obvious. Stereos generally don't use compensating eyepieces, so optically speaking, any good infinity 10x/25, 23 or 22 will do the job, except for the 4mm height difference which throws out the zoom parfocality.

If the Nikon UW head is a compound microscope type from an Optiphot, for example, the 445111 and equivalents will work fine if they're lifted and clamped 4mm higher than the stop. Not just in theory; I've done it.

Scarodactyl wrote: ↑

Fri Sep 23, 2022 9:04 pm

Here's my workaround:

With 3d printed clamps you can hold those chepa Chinese ultrawides right on the ocular and get parfocal viewing. I need to put the file up somewhere.

I just printed another one of these adapters to try on my own m7a and I can confirm it still works. Great parfocal ultrawide views for 50 bucks and a bit of filament.

I don't get it... on all my Wild/Leica stereos, the correct position of any of the compound microscope eyepieces is 4mm below the lowest position they can get to... that is, if I hacked 4mm off the eyetubes they'd be fine. How do these printed adapters work?

The chinese uw eyepieces are unusual, in that all the optics are in the top cap and the 23.2mm stem can unscrew entirely. This adapter threads in to the optics and slides onto the outside of the ocular tube to allow the optics of the eyepiece to sit a bit lower than they do with the stem installed.

Got it, nice job. Might try something like that with Zeiss Pl 10x/25s as they're built the same, i.e. all the optics in the top bit. I'm inclined to use FN 25 eyepieces as I've established that the 10x/25 eyepiece image is sharp and focused edge to edge, on my newer stereos anyway (including an M651, which it seems you may have, or one of its cousins at least), and I'm a bit addicted to that huge 55 degree angle of view. Why Wild and Leica stuck to FN 21, I don't know, I asked Leica UK, they didn't know, and they sent the question to Germany and they didn't know either. I'd say the early Wild models probably maxed out at 21, but all the MZ series for example have superb optics (despite the cheapo plastic outside) especially if you stick a planapo on and easily handle FN 26.5 (Nikon). Yes, expensive...

The chinese knes give about a 25mm fn when the 23.2mm stem is removed.
They limited it to 21mm because many of the more advanced heads can't deliver more than that (ie the low profile, ergo heads etc). Some intermediate attachments can also bottleneck the FoV. So 21mm works in all situations even if it's throwing away potential good image in some cases. The newer ones are up to 23mm though iirc with eyepiece compatibility with the s line.

Nice to find FN 25 after removing the insert.

I've had a chance to test a Zeiss Pl 10x/25 in the Leica low profile and ergo heads, and I still got a clean FN 25. I don't have every intermediate attachment so couldn't test with a phototube for instance (my low profile is a trinoc). So I'm thinking the early Wilds may have had more limited FoVs, but again I don't have anything pre M8 to check.

This is purely academic for me of course, as adapting 10x/25s to my stereos seems doable with some kind of collar whether 3D printed or lathed.

I actually got a Zeiss Universal running on 10x/25s by sawing off the 23.2mm tubes and soldering on 30mm tubes. Apart from slight softness at the periphery it gave a great view. Of course, no LCA compensation but I was using Nikons so no prob.

It may be some of the newer leica heads don't limit it the same way as the older Wild ones. A friend has an ultra low profile surgical ergo head which did apparently limit the FoV down to about 21mm, but I dosn't see that in person and I didn't exactly grill him over it.

If I may add a couple more questions. First, my Wild is not parfocal throughout the zoom range, and needs large focus adjustment from minimum to maximum zoom. I assume this is because of the 16x occulars, and is not a problem for me, but more a theoretical question. Second, I have the photoport set up very closely to being parfocal with the eyepieces, and it holds that relationship throughout the zoom range. My question has to do with the magnification I see in the photoport. It matches what I see in the eyepieces exactly, as close as I can tell. I am using direct projection with no intervening lens. I don't understand how the apparent magnification I see in the eyepiece, being objective x eyepiece, matches that in the photoport which as far a I know represents the image shown by the objective alone. Does that mean that someone using a 10x eyepiece would need reduction optics in the photo path for what they see in eyepiece to match what the camera captures? Thanks.

sreynolds wrote: ↑

Tue Nov 15, 2022 11:49 pm

If I may add a couple more questions. First, my Wild is not parfocal throughout the zoom range, and needs large focus adjustment from minimum to maximum zoom. I assume this is because of the 16x occulars

Not unless theyre incompatible and also probably extended a ways out.

sreynolds wrote: ↑

Tue Nov 15, 2022 11:49 pm

I don't understand how the apparent magnification I see in the eyepiece, being objective x eyepiece, matches that in the photoport which as far a I know represents the image shown by the objective alone. .

Simple. Your eye has a ~23mm lens in front of it which reduces the image down to fit your retina's size.