Parfocality of Leica/Wild stereo objectives?

[Rorschach]

Has anyone got practical experience of this or knows a resource on which of the objectives are parfocal with each other? I am mainly interested in Plan and Planapo objectives.

It would be great to find out if some of the old Wild Plan or Planapo objectives are parfocal with each other or with newer Leica Plan/Planapo objectives.

I am thinking of adding an objective slider to my Wild stereo at some point. It's a great way to have a huge zoom range, without paying ridiculous amount of money for one of the new Leica stereos that have a very large zoom range. For the slider to work optimally, the two attached objectives should of course be parfocal. An optimal combo would be 1) either a 0.6x or 0.5 Planapo and 2) a 1.5x/1.6x/2x Planapo.

[Scarodactyl]

I don't think any of them are parfocal. They do have an adjustment in their kombistereo and later fluocombi accessories to move the high magnification compound objective up or down until it is parfocal with at least one of the other objectives since refocusing at high mag is troublesome, but aside from that I think it's usually expected you will refocus when changing over. Olympus does have a line of parfocal objectives for their szx line, but my earlier szh with a 1x and 2x just has to be refocused. Nikon's motorized version of their AZ100 automatically refocuses and rezooms to mai tain the same mag when you change objectives which is neat.
It would be possible to adjust the position of the objectives to get them parfocal. I have a feeling this would introduce some abberations and maybe reequire impractically long extension.
Even if you need to refocus it is totally worth it. Having multiple objectives is better than a wider zoom range almost all the time. I hope you'll post about the process, as I've wanted to do the same at some point.

[Rorschach]

Thanks for the extra info. I agree, it is definitely worth it, even without parfocality. At work we have a top end Zeiss with an objective revolver for three lenses, and each objective has two positions: stereoscopic view and axial (plus fibre optic ring light for each six positions). All lenses are parfocal. It is absolutely great!

I will certainly post here when I get this project going. I have several Wild/Leica Plan and Planapo lenses already, with different magnification factors. The only obstacle is the price of the slider - new ones are expensive and I haven't been able to locate used ones.

[Scarodactyl]

Yeah, it is weird how rarely they get made given what a boost they give to performance for a relatively simple mechanical part. Even when meiji cloned the szh for their rz series they didn't make an objective changer for it. It shouldn't be too difficult to make one, but given how expensive these objectives are I would be nervous about dropping one. If I try it I'll probably do a proof of concept with cheap aux lenses on a greenough style.
As a side note, I have no idea why Wild decided their axial positioning should involve moving the entire body of the microscope to one side instead of the objective. Their engineering is ususlly so nice, but that was such a weird solution.

[Scarodactyl]

Old thread, but I wanted to correct the record--older Wild/Leica objectives are not parfocal but they changed most of the latest batch of objectives to be (all laid out in the M205 manual). These are usually too recent to be available used though. That said, these objectives are all infinity corrected so they can tolerate some extra space between objective and zoom lens, which may give enough wiggle room to make them parfocal.

[Macro_Cosmos]

Mitutoyo's QV-Objective line are all parfocal, need the small black tube add-on. I'll measure the length if anyone shows interest. These tubes can be bought from Thorlabs at pretty cheap prices, as Thorlab's SM1 tubes have threads that work with Mit's M26x0.706 threads.

QV-objective line require a 100mm tube lens, they are used on Mitutoyo's metrology measuring rigs. Sometimes they can be had for very cheap prices. The 2.5 and 5x ones work really well with 200mm tube lenses on fullframe. With ordinary 100mm tube lenses, the mid-corners absolutely suck.

[Scarodactyl]

Are they parfocal with the normal m plan apos? I know the initial theory that they were just rebranded m plan apos with a different tube length quoted didn't work out, but they do seem like a pretty minor variant at least externally.

Alas, though, unless you have Leica's fancy FL-III setup with a beamsplitter to put the image onto both light paths these wouldn't be suitable for stereo usage.

[Macro_Cosmos]

Are they parfocal with the normal m plan apos? I know the initial theory that they were just rebranded m plan apos with a different tube length quoted didn't work out, but they do seem like a pretty minor variant at least externally.

Alas, though, unless you have Leica's fancy FL-III setup with a beamsplitter to put the image onto both light paths these wouldn't be suitable for stereo usage.

Not sure about the parfocalbility with normal M Plan Apos, but they are for sure not reskinned M Plan Apo lenses. Mitutoyo also offers Z-objective lenses with rather low magnification for CNC measuring systems {?}, if I recall correctly.

I have seen parfocal tube add-ons for M Plan Apo lenses, so I suppose they are? I cannot say for sure.

[Scarodactyl]

One of these rare and expensive nosepieces came up on eBay
https://www.ebay.com/itm/223962580446
Same seller has some of the new planapos, including the one with a corrective collar to account for water over the sample. It is insanely expensive but maybe they'll take offers.

[Macro_Cosmos]

One of these rare and expensive nosepieces came up on eBay
https://www.ebay.com/itm/223962580446
Same seller has some of the new planapos, including the one with a corrective collar to account for water over the sample. It is insanely expensive but maybe they'll take offers.

$41 shipping too.
Good luck to them. Wow that's expensive.

[Scarodactyl]

Indeed, especially since you could likely make one yourself if you couldn't find another brand to adapt on (olympus https://www.ebay.com/itm/323349257468) or even an enlarger turret (like this https://www.ebay.com/itm/202764497681 but these are too small for leica-sized 65mm objectives)
Sometimes that make offer button can work in your favor though.

[Rorschach]

Yeah, don't have the kind of money right now. Not even if the seller accepted a discounted offer...recent foray into the realm of the Orthoplan has destroyed my finances.

[Rorschach]

The revolver and one of the two Planapo 2.0x corr. objectives should disappear from Ebay soon. It may be that someones work place needed the special capabilities provided by those instruments

[Scarodactyl]

Cool! If you get a chance I'd love to hear how well that corr objective works.

[Rorschach]

Cool! If you get a chance I'd love to hear how well that corr objective works.

I see that I forgot to report back in this thread. I think I did write something about this somewhere but maybe that was on another forum. Anyway, the 2x corr. seems to do what it says on the tin. I did a visual eye-test comparison with it and the basic Leica Plan Apo 2x that I personally own on specimens in half a cm of ethanol. You do get some extra resolution and detail with the corr. when you dial in the compensation. This is useful for example to people who need to id specimens in water or ethanol (which have almost the same refractive index), which is everybody doing freshwater benthic invertebrate work, maybe some others too. It really means that you'll have much less need to separate small parts like mouth parts to be put on a slide and then under a compound scope. Improves the workflow which is important because you're typically going through several hundred specimens from many dozen different taxa groups on a full day of id work. Therefore: approved and recommended.

Now we have the Leica 205C that has this lens on a Leica MDG32 BF/DF/Rottermann base, which will give extra tools for translucent or semi-transparent specimens. Again, that reduces the need to go back and forth between the stereo and a compound.