Leica PL Fluotar 100x/0.90 Dry

[SpaceGrey]

Does anyone have any experience with Leica 100x Dry fluotars?
There seemed to be a number of them out on eBay for surprisingly low asking price for a that level of objective.
I wonder if it’s worth getting one.

[PeteM]

Two things to consider. First, these are meant for reflected, not transmitted, light. So they won't be in focus for slides with a cover slip. Might be OK for smears. Second, while it's handy not to have to oil an objective, I've never gotten as good resolution from a dry 60x and higher objective as one oiled.

If it's reflected illumination you're using, I'd expect the objective to be fine. Closest thing I actually have is a BF/DF high power Leica Fluotar -- and it's fine for what it is.

[einman]

I have used them and find the images to be less than acceptable. As mentioned the highest I go with a dry objective is 60-63X.

[MicroBob]

Hi together,
I frequently use a Zeiss Jena dry Apo 40/0,95 objective with correction collar, very useful on my Phomi with Optovar (1,25x, 1,6x, 2,0x). At 500x combined magnification it gives a nice field of view and a very crisp image. At 640x image quality is still good, and detail is easier to see. At 800x magnification there is no real gain in visible detail while the field is reduced.
A 100/0,9 dry objective is probably intended for a special purpose in routine microscopy where the object is easy to find and the high magnification makes identifying on medium fine detail easy on the eye. So not attractive for the amateur.

Bob

[Marco68]

Two things to consider. First, these are meant for reflected, not transmitted, light. So they won't be in focus for slides with a cover slip. Might be OK for smears. Second, while it's handy not to have to oil an objective, I've never gotten as good resolution from a dry 60x and higher objective as one oiled.

If it's reflected illumination you're using, I'd expect the objective to be fine. Closest thing I actually have is a BF/DF high power Leica Fluotar -- and it's fine for what it is.

Hi PeteM
do you mean these ones :
https://www.ebay.com/c/826377402
https://www.ebay.com/itm/Leica-HC-PL-FL ... Sw0LleLXht

are not meant for compound microscopes ? 100$ too good to be true

[PeteM]

They do go on a compound microscope - but they are not meant to be used with regular slides and specimens with coverslips, which typically add around a .17mm bit of glass.

The most common 100x biological objective is meant to match the refractive indexes of its glass with an oil immersion, then a thin glass cover slip, then the specimen just below that cover slip. At high magnifications there is very little depth of field and slight refractive index mismatches degrade the image.

There are also "dry" 100x objectives with a .17mm cover slip correction. These typically aren't as good image-wise as oil immersion, but provide OK images.

What you have listed is a "dry" (no oil immersion to match refractive indexes) with no cover slip correction. It's not sealed for oil. And it's not corrected for a cover slip.

The "O" on these means they aren't meant for cover slips. You'll sometimes see a "O" with an oil immersion objective that can work OK. This isn't one of them - no oil immersion marking.

Instead, these are meant for subjects without a cover slip -- often reflected light objects, such as metal surfaces. They might give a satisfactory transmitted light image with something like a thin blood smear, minus the cover slip. They should be good for something like the silicon wafers that Bob showed earlier if you have a microscope with an "epi" reflected light illumination capability.

[MicroBob]

Heat fixated and stained blood smears are quite robust - you can observe them with oil immersion, wipe off with petroleum ether again and again. I would guess that this type of objective is for counting blood cells as is offers a nice enlarged view.
The Epi objectives typically have medium to high numerical apertures. My 40:1 Zeiss West HD objective already has an n.a. of 0,85.

[PeteM]

Bob, not sure about that. Could be wrong, but every Leitz objective I've seen that's designed and sealed to handle oil immersion is marked oil or oel. Pretty sure these are meant to be used dry and with no cover slip. Most likely (the Israeli ones) for something like semiconductor inspection or other dry epi uses. I do agree they might work OK for blood smears, but dry or at some risk of oil intrusion.

[MicroBob]

Hi Pete, sorry that I didn't make this clear: Of cause these objectives are for dry use. I think they are used for routine counting jobs were a good magnification and basic resolution are good enough. What I wanted to say: The blood smear slides are quite robust and are not covered in routine use, even for longer storage. So they are in the right condition for the use of there objectives.

[Marco68]

Thanks. i am interested to see microorganism ..therefore it is definetly not a good deal for me

In the price range of 100-250$ I have found also these ones:

https://www.ebay.it/itm/Leica-Microscop ... SwvNhdNLUH


https://eur02.safelinks.protection.outl ... reserved=0

It say "Plan 100x/1.25 OIL" and "HI Plan 100x/1.25 oil" . I am not sure of the difference between Plan, C Plan (that I will get on my Leica DMLS) , Hi Plan, N Plan and I could not find the code 13613243 and 506238 (indicated on the objectives of the above).
In any Leica catalogue. Any hints ?

thanks !

[Marco68]

I have found this that explain the difference between Hi Plan and N Plan objectives : https://www.leica-microsystems.com/prod ... e-classes/

but still "C Plan" or simply "Plan" are not explained. Maybe are these older models ?

[Marco68]

Keep investigating and I found the answer ))
Plan and Hi Plan objectives are used in the "entry level" Leica DM500/750
Plan objectives => FOV 18
Hi Plan objectives => FOV 20

[Marco68]

Now..my theorical question:
I understood that the Field of view depends from the eyepiece field number and from the total magnification.
So the objective should not have any influence on the FoV. So..not sure why Leica indicate the FoV on the objectice

[Marco68]

I make the questions and I answer myself

The objective FOV that Leica states for the objectives is just the maximum Field of view where the Flatness of field is guaranteed...

I suppose therefore that if my eyepiece has a FOV of 22 it would make sense to have Plan objective designed to guarantee the plan field correction up to 22 mm ...

[MicroBob]

Hi Marco,
the human eye's vision is not very sharp towards the borders. So it is more a question of what your camera adaptation covers than what you visual eyepieces cover. These values for planar field are not that high. As far as I know the 160mm Zeiss West Plan objectives were calculated for a 25mm planar field. The Leitz NPL Fluotars for 24mm, the Leitz Plan objectives for 28mm. Maybe this is stated an a different definition of "planar".

Bob

[Marco68]

Thanks MicroBob, reading on https://www.leica-microsystems.com/prod ... e-classes/ I see that for entry level objectives they have FOV starting from 18/20 mm but I understand what you say that I would probably not even notice the difference with my eyes ...