objective nomenclature

[saltheart]

My 1st post so go easy. I have discovered a Leitz Orthoplan while clearing out an old lab It has all the bells and whistles including additional nose piece and objectives. Can someone tell me the difference between Pl40/0.65 and a NPl40/0.65. There are two other objectives denoted NPl and all three have Interf-Kontrast T scribed in red on their barrel. Thanks.

[Charles]

Can someone tell me the difference between Pl40/0.65 and a NPl40/0.65. There are two other objectives denoted NPl and all three have Interf-Kontrast T scribed in red on their barrel. Thanks.

The Pl means Plan and the NPl means Normal Plan. They say the NPl is better than the Pl. Interf-Kontrast T scribed in red on the barrel means they can be used for Interference Contrast or DIC but they can also be used for regular microscopy. If there are IC elements, IC condenser and IC objective adapters, along with a polarizer and analyzer, you would have a DIC system.

[MichaelG.]

The Pl means Plan and the NPl means Normal Plan. They say the NPl is better than the Pl.

.
Interesting ... Does ‘Normal’ in this case mean ‘perpendicular to’ ?
i.e. the image is not only flat, but accurately perpendicular to the optical axis

MichaelG.

[apochronaut]

There are numerous designations leading up to the plan designation and the plan designation is entirely dependent on which eyepiece the manufacturer has decided to rate the objective as plan with.
NPl has also been linked with the term Neoplan, which is usually associated with a narrower field of view while having plan performance, when compared to Plan. When judged at, as an example a 20 mm f.o.v. with a 10X eyepiece, a neoplan would function similarly to a semi plan or SPl, although possibly slightly better. There is also the situation where manufacturers utilized fairly complex lens formulas during the 70's and 80's in order to achieve plan performance, as many as 12 lens elements. Neoplans I have looked at have very close to plan performance but with many fewer lens elements , yet with a new design and at less cost to the user.

[PeteM]

Can someone tell me the difference between Pl40/0.65 and a NPl40/0.65. There are two other objectives denoted NPl and all three have Interf-Kontrast T scribed in red on their barrel. Thanks.

. . . They say the NPl is better than the Pl. . . .

FWIW, I've heard it the other way - that "Plan" provides a wider plan field of view and that "NPL" is narrower. Somewhat like the difference between Olympus "SPlan" (up to 26mm field) and "DPlan (20 mm or so field). Most of the Leitz 160mm tube objectives I've seen, however, are marked "Plan" and not "PL" - so maybe there's the difference?

Also might be the NPL is somewhat newer and less strain for DIC - if that was the meaning??

Somewhat might know for sure.

[Charles]

PeteM, You are probably right. I am getting old and my memory is not what it use to be. But Pl (Plan) probably does have a flatter FOV than the NPL. Here is a discussion about Pl and NPL: https://www.photomacrography.net/forum/ ... d74c4171f1
There are many NPl objectives which are not designated with Interf-Kontrast. Just like pol lenses, the ones with Interf-Kontrast are certified for IK?

[MichaelG.]

Looks like I will remain confused for a while longer

... I was hoping the inner truth had been revealed

MichaelG.
.

Edit: Perhaps the best evidence might come from a price list !!

[saltheart]

Thanks for all the input, it seems the more you learn the more you realise there's more to learn. I'm pretty sure I have the other accessories for DIC.

[gastrotrichman]

I understand that Leitz "locked" their DIC objectives in place. If yours are not locked in place, you will need to go through a procedure to get each objective rotated to a position where it takes maximum advantage of the DIC condenser. If they are locked in place, don't unlock them.

[apochronaut]

Looks like I will remain confused for a while longer

... I was hoping the inner truth had been revealed

MichaelG.
.

Edit: Perhaps the best evidence might come from a price list !!

I don't have a price list handy but I have seen one for the group of objectives listed for the AO/Reichert series 400 microscopes. They listed three sets of objectives over the 16 or so years that the microscopes remained on the market.

5 - Neoplans, 8 Planachros and 4 Planfluor, although not all showed up at the same time in catalogues. Comparing similar objectives, for instance a 10X .25 Neoplan against a 10X .25 Planachro there was a small price differential with the Planachro version being about 15% more in cost. You can also see from representative instruments around, that the Neoplan series of objectives were pitched at a more budget conscious market, with many of the microscopes carrying a 4 place nosepiece sporting Neoplans.

[MichaelG.]

Looks like I will remain confused for a while longer

I don't have a price list handy but I have seen one for the group of objectives listed for the AO/Reichert series 400 microscopes. They listed three sets of objectives over the 16 or so years that the microscopes remained on the market.

5 - Neoplans, 8 Planachros and 4 Planfluor, although not all showed up at the same time in catalogues. Comparing similar objectives, for instance a 10X .25 Neoplan against a 10X .25 Planachro there was a small price differential with the Planachro version being about 15% more in cost. You can also see from representative instruments around, that the Neoplan series of objectives were pitched at a more budget conscious market, with many of the microscopes carrying a 4 place nosepiece sporting Neoplans.

.

Many thanks for that useful information

The unfortunate ambiguity seems to be whether N stands for Normal [as was suggested earlier] or for Neo
... or [heaven forefend] both !

MichaelG.

[apochronaut]

I suppose where they are just designated as NPlan that might be a question . In this case the catalogue explicitly says Neo Plan.

[Charles]

Let me add some clarity. Each manufacturer may have their own naming conventions and abbreviations but for Leitz NPl is Normal Plan. See attached document from a Leitz manual.

Leitz Objective Doc.PNG (487.85 KiB) Viewed 5897 times

[MichaelG.]

So it looks like perhaps ‘normal’ means ‘ordinary/common-or-garden’ not anything geometrically special.

Confusion continues to reign !

MichaelG.

[apochronaut]

The concept of plan , really is a variable one and entirely dependent on the f.o.v. NPl , probably implies planarity with a normal f.o.v., which is probably somewhere around 18mm. To achieve a wider field, with wider planarity, a whole different set of optics would be necessary.


There is something else with planarity that gets overlooked, though. We are accustomed with modern systems to expect, not only planarity but complete correction for all of the optical aberrations that occur the farther one goes off axis. When I say planarity , I am meaning inclusive of flatness of field. Some would dispute that the two are synonymous. It is possible to have planarity, yet still have a degree of coma at the extreme edge of the field for instance. Flatness of field and coma require different corrections. It would be theoretically possible too, to have a field completely corrected for all peripheral aberrations, except curvature of field. Early attempts at planarity with microscope optics, seemed to be there, where there was reasonable control of peripheral aberrations but a small amount of curvature still plagued the off axis extremeties. Field flattening, seemed to come along a little later. Modern semi-plans are somewhat representative of that type of design.
In the 60's Bausch & Lomb had only Flat Field objectives. These seem almost completely plan , if one uses them at a "normal" f.o.v., around 18mm but B & L also made 20mm eyepieces and stretched over that breadth, the Flat Field eyepieces were still flat but not terribly severe edge distortions creep in.....so flat field yes but not quite plan, at 20mm. Around 1973 or 4, the catalogue #'s changed and the designation Planachromat arrived. The Planacromats were superior in overall peripheral corrections, even beyond 20mm and had upgraded contrast and resolution to boot, yet also maintaini the previous objective range's flatness.
They also made Flat Field Apochromats. Now they not only have a flat field but benefit from the apos superior off axis corrections, so they function like what other mfg. would call plan. Later, when the Flat Field Achromats were redesigned into Planachromats, the Flat Field Apochromats were left as is, albeit , it would have taken a considerable effort to redesign those. They did however redesign a few of the Flat Field Fluorites into Planfluorites but the overall improvement in the Planachromats was such, that by and large they succeeded in achieving an equivalent performance level from them to match the previous Flat Field Fluorites.
,

[MichaelG.]

Here’s a similar discussion, from 2009 :
https://www.photomacrography.net/forum/ ... d74c4171f1

If this statement is true:

I´ve got the original Leitz booklet in front of me. In there are listed and explained all abbreviations the Leitz people have used during the "160 mm Era". And definitely, NPl means "normal plan", i.e., marks lenses, which have a flat-field correction for a field number of up to 20 ( as opposed to Pl lenses, which are corrected for the extra large field number of 28 ).

Then the only pity is that Leitz did not think to mark the Pl objectives WPl ...

MichaelG.

[PeteM]

I understand that Leitz "locked" their DIC objectives in place. If yours are not locked in place, you will need to go through a procedure to get each objective rotated to a position where it takes maximum advantage of the DIC condenser. If they are locked in place, don't unlock them.

I've done a bit of experimenting with a set of the Leitz ICR objectives with the ICR prisms mounted directly above them - then all screwed into an RMS mount. They are certainly locked from roration. However, my guess is that the reflected image should be about the same since the light passes through the same prism twice - once down to the opaque specimen and once reflected back up on its way to the eyepieces. Alignment "should" be guaranteed. Perhaps the locking in position was such that the diagonal shear line would be at some visually pleasant rotation, such as 45 degrees??

The surprise for me is that these are pretty decent objectives AND can give good transmitted DIC when paired with a PZO DIC condenser. The fuss, of course, would be rotating each individual objective prism to line up with the appropriate condenser prism. In my own experiment, I simply rotated the entire condenser body or unscrewed the objective-prism pair a bit to get alignment and confirm the concept.

Point all this out, because it might be a somewhat affordable way of getting both reflected and transmitted DIC?

[Scarodactyl]

It would be theoretically possible too, to have a field completely corrected for all peripheral aberrations, except curvature of field.

This is a very good point, and seen on some prized lenses and objectives, giving the sort of abberations that 'stack out'. I think the Lomo 3.7x is an example. While not as ideal when viewing a single image or through eyepieces, for modern photomacrography this is a very acceptable compromise.