I have a separate turret for my Leitz Diaplan that I have been filling with strictly oil immersion objectives. My most recent acquisition being the 25X/0.75 na fluor immersion objective. With the addition of this objective the turret now has a 25X/0.75 fluor; 40X/1.4 na Fluor; 63x/1.4 na Fluor and a 100X/1.32 na Plan Apo. It has taken me 2 years to slowly purchase these objectives. The only dry objective on the turret is a 10x/0.30 Fluor. I wanted a turret with only oil objectives to eliminate the possibility of ruining my 40X dry planapo objectives etc. The Leitz Diaplan has quick change turrets. I have three turrets one with dry objectives, one with phase-contrast and the oil immersion.
While these objectives offer superb images the fact I only have a 0.90 achromatic condenser means I could potentially squeeze more resolution out of them. I need the aplanatic-achromatic top na 1.4 for my universal condenser.
With that said if anyone has one or happens to come across one for sale please let me know. I plan on putting this post in the wanted ads as well.
Oil immersion objectives
Re: Oil immersion objectives
So I did a quick and dirty test. I compared my Leitz 25X/0.55 Fluotar dry objective against my 25X/0.75 Fluor oil immersion objective. I DID NOT OIL the condenser. Given the NA of the immersion objective is less than 1.0.
Both dry: the 25X/0.55 objective has superior color/contrast whereas the resolution appeared to be equal to slightly better for the 25X/0.55 objective.
I oiled the the 25X/0.75 na immersion objective and compared once again. Adding the oil, as would be expected, improved resolution, color and contrast significantly. DOF appeared to be less than the dry objective but the resolution was superior. It would be interesting to compare say a dry objective with na and magnification to a comparable oil immersion objective to determine the benefits, if any, of oil immersion over dry at the same NA and magnification.
Disclaimer: Your findings may vary based on equipment.
Both dry: the 25X/0.55 objective has superior color/contrast whereas the resolution appeared to be equal to slightly better for the 25X/0.55 objective.
I oiled the the 25X/0.75 na immersion objective and compared once again. Adding the oil, as would be expected, improved resolution, color and contrast significantly. DOF appeared to be less than the dry objective but the resolution was superior. It would be interesting to compare say a dry objective with na and magnification to a comparable oil immersion objective to determine the benefits, if any, of oil immersion over dry at the same NA and magnification.
Disclaimer: Your findings may vary based on equipment.
Re: Oil immersion objectives
Hi, eiman, interesting working concept, your turrent of oil-objectives. Does the working distance of these oil-objectives permit wetmount slide observations for you? What sort of observing do you do with this oil-immersion series? Is it image captures, more so than our tremendously forgiving and adaptable visual system which is the true benefit of your oil-objective series?
How 'squeemish' are you regaurds to observing with these near to edge of a wetmount coverslip slide prep? I ask as I dread 'gunking' my 60X Planapo with methylcellulose waters from under the cover slip..so I avoid the border areas of my slide preps.
I'd love to collect 160 TL water immersion objectives...my LOMO WI 70X has limited use with my workhorse stand. an image of that oil-objective turrent would be sweet to admire here (hint!). Charlie guevara
How 'squeemish' are you regaurds to observing with these near to edge of a wetmount coverslip slide prep? I ask as I dread 'gunking' my 60X Planapo with methylcellulose waters from under the cover slip..so I avoid the border areas of my slide preps.
I'd love to collect 160 TL water immersion objectives...my LOMO WI 70X has limited use with my workhorse stand. an image of that oil-objective turrent would be sweet to admire here (hint!). Charlie guevara
Re: Oil immersion objectives
Charlie,
When I observe specimens wet mounted I generally use just enough to fill the space under the coverslip and mop up excess with a tissue. When using an immersion objective you use the least amount of oil that is necessary, or, like coverslips, the thickness impacts reolution.
The intent once my system has been optimized is for photography and taxonomy.
Here is a photo of my immersion turret.
When I observe specimens wet mounted I generally use just enough to fill the space under the coverslip and mop up excess with a tissue. When using an immersion objective you use the least amount of oil that is necessary, or, like coverslips, the thickness impacts reolution.
The intent once my system has been optimized is for photography and taxonomy.
Here is a photo of my immersion turret.
Re: Oil immersion objectives
Thanks for the savory view of your oil-objective series, eniman. Is it only the 100X objective which has a correction collar in this nose-piece setup? Now I'm keenly curious of what subject/material areas you employ a 100X oil-objective for taxonomy studies and documentation ( diatoms, protozoa, fungal spores, pollens, microalgae..?). I'm enthralled with your arachnid wisdom you kindly shared over the years, einman.
Of course regardless of how much immersion-oil one plops ontop the coverslip...once proper focus is achieved ( I drop down and touch the oil droplet, then I rack up and break oil-bridge contact, then I drop down into oil contact and achieve focus with my oil (or my one rarely used WI objective) objective...once focus is achieved...it is rather constant , the film thickness of oil-bridge between coverslip and objective lens face. As with waters under a coverslip...one gets a sense of volumes to employ before a slip is placed, or oil applied.
Do you regularly use your oil-objectives correction collars? Is it a trick to snuggle fingers amongst the quintuple objectives, to use the correction collar ( I find it tricky!) ?
A very tempting setup indeed, you share with us, thank you, eniman. Charlie guevara
Of course, of course oil-bridged objectives do not require a correction collar...my bad, einman...thanks for sharing this unique nose-piece series of oil-objectives!
Of course regardless of how much immersion-oil one plops ontop the coverslip...once proper focus is achieved ( I drop down and touch the oil droplet, then I rack up and break oil-bridge contact, then I drop down into oil contact and achieve focus with my oil (or my one rarely used WI objective) objective...once focus is achieved...it is rather constant , the film thickness of oil-bridge between coverslip and objective lens face. As with waters under a coverslip...one gets a sense of volumes to employ before a slip is placed, or oil applied.
Do you regularly use your oil-objectives correction collars? Is it a trick to snuggle fingers amongst the quintuple objectives, to use the correction collar ( I find it tricky!) ?
A very tempting setup indeed, you share with us, thank you, eniman. Charlie guevara
Of course, of course oil-bridged objectives do not require a correction collar...my bad, einman...thanks for sharing this unique nose-piece series of oil-objectives!
Last edited by charlie g on Thu Dec 28, 2017 1:48 am, edited 2 times in total.
Re: Oil immersion objectives
Charlie,
Actually it is the 40x/1.3 na objective that appears to have the correction collar. That is not actually a coverslip correction collar rather it is an iris for varying na from 0.8 to 1.3.
Dry objectives used with air between the front lens and cover glass, variations in cover glass thickness and dispersion properties can become a source of chromatic and spherical aberrations requiring the use of a collar which moves the lenses internally.
However oil immersion objectives are designed to be immersed in oil having a set RI of 1.515 as I recall. The oil eliminates the need for a cover slip correction collar, as it eliminates the aberration inherent in dry objectives where light has to cross from the cover slip having one RI (~1.5) through air having another RI (1.0) and then to the objective lens with yet another RI.
Actually it is the 40x/1.3 na objective that appears to have the correction collar. That is not actually a coverslip correction collar rather it is an iris for varying na from 0.8 to 1.3.
Dry objectives used with air between the front lens and cover glass, variations in cover glass thickness and dispersion properties can become a source of chromatic and spherical aberrations requiring the use of a collar which moves the lenses internally.
However oil immersion objectives are designed to be immersed in oil having a set RI of 1.515 as I recall. The oil eliminates the need for a cover slip correction collar, as it eliminates the aberration inherent in dry objectives where light has to cross from the cover slip having one RI (~1.5) through air having another RI (1.0) and then to the objective lens with yet another RI.
Re: Oil immersion objectives
Charlie,
When focused on protozoology I like to try and identify organisms to at least the genus level. Ideally I would like to drill down to the species level. Both require looking at very small structures on the organism. The higher the resolution the better.
I do not use my compound scopes for entomology although I have used the lower magnification objectives combined with epi lighting for some smaller species of dacetines. I am leaning more towards my stereoscopes combined with some macrophotography using compound objectives and stacking.
I will share more about my projects in the coming months. For now I am trimming my collection to make more room and reduce clutter.
When focused on protozoology I like to try and identify organisms to at least the genus level. Ideally I would like to drill down to the species level. Both require looking at very small structures on the organism. The higher the resolution the better.
I do not use my compound scopes for entomology although I have used the lower magnification objectives combined with epi lighting for some smaller species of dacetines. I am leaning more towards my stereoscopes combined with some macrophotography using compound objectives and stacking.
I will share more about my projects in the coming months. For now I am trimming my collection to make more room and reduce clutter.