Leitz SM-LUX Focussing

[vendav]

I have recently bought a SM-LUX fitted with a full set of Leitz 170mm objectives none of which can be brought to focus.
The stage when fully raised is approximately 4mm below where it needs to be to achieve focus.
I have tried other (Olympus) "short" objectives with the same result.
However, a set of 160mm objectives work perfectly.

I cannot find a stop which might limit the stage movement and am puzzled as the SM-LUX is frequently offered with 170mm objectives and, it seems, just as frequently with 160mm objectives. I assumed that this inferred that the stand would accept either.

Is my assumption wrong? Are there different models to suit the different tube length objectives, and mine are mismatched? Or am I being a complete idiot and overlooking a cleverly concealed stop?

I have bought a set of extenders which enable the instrument to be used "as is" but this, obviously, is not ideal.

Any help/explanation would be greatly appreciated.

Kind regards,
David

[Brad_]

The SM-LUX is made for 45mm parfocal objectives. It sounds like
you have the shorter 37mm objectives which were "standard" on
1930-ish Leitz stands.

There are PLEZY adapters, short tubes with a lens, that will
bring the lengths up to 45mm. They're a bit expensive, $30 -$50,
if you can find them. Most of the ones I see on eBay are already
attached to objectives, bringing the price higher.

Sorry.

Brad

[vendav]

Thanks Brad - so when I see an SM-LUX advertised with 170mm objectives these will be to the DIN 45mm parfocal standard? (unless they're mismatched like mine of course!)

Kind regards,
David

[mrsonchus]

Thanks Brad - so when I see an SM-LUX advertised with 170mm objectives these will be to the DIN 45mm parfocal standard? (unless they're mismatched like mine of course!)

Kind regards,
David

Hi vendav, I recently acquired an excellent Leitz Orthoplan that, like your 'scope, has a 170mm tube-length by design. I can tell you a couple of things for certain, in the context of my own equipment admittedly, as the two 'scopes are very, very similar in their optics (differences are in the illumination path length primarily, the condenser, stage position, objectives, tube-lens and eyepieces are virtually the same technically).

Official Leitz memorandum states that the 160mm TL objectives are fine to use in the 170mm system with no noticeable difference in image properties above x16.
This is certainly true in my experience as I have a couple of 160mm objectives (a Jena x40 PlanAchromat and a x63 FL) that both give beautiful images - I also have a 170mm TL x40 FL that enabled me to compare the 160mm Jena to this 170mm x40, they were almost identical, a little more planarity with the Jena and a little higher contrast with the 170mm - as per their specs irrespective of the TL.

As far as the 37mm 'shortie' objectives compared to the more common (std) 45mm objectives, I also have both types and can assure you that their difference lies only in the fact that they are definitely not parfocal within the same nosepiece - the 37mm needs the stage a lot higher than the 45mm - dodgy as changing from a 37mm to a 45mm without lowering the stage first will cause a nasty crash!
The answer to that minor problem is the 'Plezzy' adapter that changes a 37mm into a 45mm with no loss or compromise of image detail & quality - the Plezzy has a 'normal' version and a 'FL' version - I have a 'normal' version that I use on a 'shortie' x53 Oel objective with excellent results.

So, from my albeit limited hands-on experience I'd say that the Plezzy adapter is a perfectly good solution to the 37mm/45mm difference and that the 160mm/170mm TL issue is a non-issue above x16.

Hope this helps a little - I've images that you may peruse if they will help also my friend.

John B

[vendav]

Hi John,

Thank you. That's quite confusing to a newcomer to the sport but a little clearer now.

As I said in my original post, I have placed a short extender (cheap Chinese without optic, not Plezzy) behind each objective and get a decent - at least to me - image, so the 'scope is useable.

I can see no easy way to raise the stage and am reluctant to attempt any major mods; I think that I will keep this one for my grandchildren to use as is.

Kind regards,
David

[mrsonchus]

Ah, when I say raise the stage - I don't mean permanently, but by the normal focusing up & down mechanism my friend. Simply that the 'shortie' objectives focus in the normal way by focusing - which moves the stage up & down, and when you come to use & focus the longer 45mm objective the stage ends-up in a lower position when focus is made. The difference is about 5mm I think.
Both 37mm and 45mm objectives will focus fine with normal focusing movements, just not in the same position of the focusing knob/s - no alterations need to be made to your 'scope.

Here are a few pictures. I was only last night using a mixture of a 37mm x54 oil objective (without the Plezzy as I only have one and have it fitted to a nice x40 at the moment) and 45mm x100 oil objective to take a close look at some pollen sections.

Here's the x100 45mm objective at focus, if the 37mm x54 next to it in the nosepiece had a Plezzy adapter fitted it would simply swing-in and be very nearly in focus too (i.e. parfocal with the also 45mm x100 seen here) requiring only a very slight focus-adjustment.

ws_45mm x100 oil objective focused.jpg (40.9 KiB) Viewed 3968 times

Without the plezzy the 37mm is nowhere near in-focus, and not of course parfocal with the x100 above. The focus of the non-Plezzy 37mm must be altered a lot, the stage will move up to the objective as you focus, by about 5mm-ish...

ws_45mm swung out 37mm swung in without focusing.jpg (41.8 KiB) Viewed 3968 times

So, here's the situation as the 37mm x54 is brought to focus in the usual way,

ws_37mm x54 oil objective focused.jpg (45.67 KiB) Viewed 3968 times

If I now swing-in the x100 without moving the stage at least 5mm-ish lower (by using the focus meachanism) the x100 will smash into the stage/slide...... The Plezzy fixes this and I can definitely say makes no difference to image quality - but does bring the 37mm and 45mm into a parfocal postion. The Plezzy works well - and I've just bought another (Flu version to go with this 37mm x54 oil objective seen above which is a Fl objective) online for £35 - money well spent in my book!

Here they are, shoulder-to-shoulder as it were - the shame of the 37mm 'shortie' x54 - look how smug the 45mm x100 looks!
But.. what's that even-shorter fellow on the end.....

ws_45mm 37mm plezzy.jpg (45.59 KiB) Viewed 3968 times

And they never called him 'shortie' again! Hussar!

ws_45mm 37mmandplezzyfitted.jpg (43.89 KiB) Viewed 3968 times

They work, and they're a very handy thing to have a couple of in your kit - enlarges your options for objectives considerably!

Hope this helps a little my friend.

John B