Expensive objectives?

[Greg Howald]

I have several microscopes. They all have finite achromatic objectives that came with them.
They sell much more expensive objectives that could easily be used with my scopes. I'm not against buying them but I wonder....
Is the purchase worth it?
I purchased some of the inexpensive plan objectives and didn't see much difference at all.
If I buy more expensive objectives....
Will I notice a difference?
Thanks, Greg

[Plasmid]

In my personal experience with mixing objectives... I've used Finite in a Infinite scope since my 40x Plan Achro ~ is AOS , and have notice very little to almost no difference at all. Plan or semiplan objectives do make a difference at least for direct observation when compared to DIN objectives.
https://youtu.be/DyC_PDonlNU

[Greg Howald]

I have an infinite 20x objective and mounted that on my finite scope. Not in the same focal plane of course but other than that I didn't notice a difference.
Greg

[Plasmid]

So, I just tried and moved all of the DIN objectives next to their counterpart Plan Acro, anything below 40x produced no difference, 40x and up I can start to see a difference in contrast, specially using a 15x WF vs 10x WF eyepiece. The cell phone pics I took do it no justice, hopefully someone with more experience in the subject can chime in. Ultimately it comes down to how good our eyesight is. I had been considering purchasing some Plan Apo objectives, but decided to save the money and spend it on a phase contrast or darkfield condenser with matching objectives I feel like its a more significant upgrade.

[apochronaut]

Low power objectives, typically have lower N.A's so are not as subject to certain optical aberrations as higher N.A. objectives, so mis-matching them in systems might not cause much of an obvious quality degradstion.
Achromatic objectives typically also, are subject to certain aberrations that more highly corrected objectives are not. When using any achromat there will be a degree of chromatic aberration, less so with some than with others. When mixing achromat objectives into a system, it is hard to know what the image should look like, unless you have a standard system objective to compare it too.So mis-matched achromats may seem o.k. with certain samples.

I see a picture of a presumably 160mm tube length objective in a nosepiece from an infinity corrected microscope above in the post. Have you compared it directly to a 10X Reichert Neoplan or Planachro? You may find some issues of spherical aberration when directly compared, that you otherwise don't notice.

D.I.N. is not a production standard that is inconsistent with the terms plan or semi-plan. Planarity has it's own ISO standard but it exists complementaty to a D.I.N. standard as well, so any plan or semi-plan objective can also be D.I.N., as long as it conforms to the D.I.N. standards, basically R.M.S. threads and a 45mm parfocality.

Whether an objective has a flat field or not is fairly irrelevant if one is always or usually viewing slides that are more than a few microns thick. Something in the sample will be in focus, so the scene would look little different between a plan and non-plan objective as long as the other corrections of the objectives are equivalent. Sometimes, and I would say often times, plan or flat field objectives are more highly corrected for coma, and lateral chromatic aberration as well as spherical aberration and astigmatism too, so they provide other benefits than just that of field flattening. Plan objectives are a must, if you are trying to interpret smears.

Objectives can be expensive for many reasons. Sometimes, it is because it is plan but it can also be because it has a higher N.A., longer working distance, a larger image circle ,be more highly colour corrected, or be made to specifications that allow different immersion mediums, such as glycerin or water. Each has it's value in the right application and I can assure you that within the parameters of that application, a standard achromat objective will not do as well, if do at all.
For most standard viewing , achromats are fine but I can also assure you that a fluorite or apochromat are in almost all circumstances, except where the ssmple is too thick, extra fine to in some cases stunning. Does a 100X planachro provide $6,000.00 worth of stunment? I would say no to that but I have a couple of those, and they cost only 240.00 for the two of them. So, the option is out there to get stunned if you so desire and it won't be too expensive.

[hans]

I've used Finite in a Infinite scope since my 40x Plan Achro ~ is AOS , and have notice very little to almost no difference at all.

I see a picture of a presumably 160mm tube length objective in a nosepiece from an infinity corrected microscope above in the post. Have you compared it directly to a 10X Reichert Neoplan or Planachro? You may find some issues of spherical aberration when directly compared, that you otherwise don't notice.

In the example with the Carlsan 40X on the Microstar IV in viewtopic.php?f=24&t=10911#p91282, hard to judge spherical aberration, but there is definitely more lateral CA (the red/blue fringes in the radial direction) than with the Reichert 40X plan achro, presumably due to the color-correcting doublet "correcting" lateral CA that is not present in the 160 mm objective:

lca-1.png (11.48 KiB) Viewed 3722 times

lca-2.png (12.8 KiB) Viewed 3722 times

[Plasmid]

I see now, this just made me realize I can deny it no longer..... I'm blind as a Bat.

[hans]

I find the lateral CA in particular hard to judge looking through the eyepieces. Trying to look at the periphery of the FOV the CA is extremely sensitive to head position, presumably related to my eyes because I don't see the same effect with a smartphone camera. Much more obvious and consistent in photos.

[75RR]

Plan or semiplan objectives do make a difference at least for direct observation when compared to DIN objectives.
https://youtu.be/DyC_PDonlNU

In that video they seem to be referring to achromats as DIN. That is a misnomer.

DIN stands for: Deutsche Industrie Norm and includes the type of thread, the parfocal distance (45mm) and the tube length (160 mm) among other things.

It has become the finite system standard.

Some infinity system objectives also share the DIN standard thread and the parfocal distance.

They are not however compatible with the finite system, just as finite objectives are not compatible with infinity systems.

Objectives from both systems can be achromat or Plan. Plan is short for Planachromat.

If an objective does not have a designation, such as Plan, Neofluar Planapo etc ... then it is assumed to be an achromat, whether it is a finite or an infinity objective.

Finite objectives usually have the number 160 (tube length) written on it while the infinity ones use the infinity symbol ∞

[apochronaut]

I've used Finite in a Infinite scope since my 40x Plan Achro ~ is AOS , and have notice very little to almost no difference at all.

I see a picture of a presumably 160mm tube length objective in a nosepiece from an infinity corrected microscope above in the post. Have you compared it directly to a 10X Reichert Neoplan or Planachro? You may find some issues of spherical aberration when directly compared, that you otherwise don't notice.

In the example with the Carlsan 40X on the Microstar IV in viewtopic.php?f=24&t=10911#p91282, hard to judge spherical aberration, but there is definitely more lateral CA (the red/blue fringes in the radial direction) than with the Reichert 40X plan achro, presumably due to the color-correcting doublet "correcting" lateral CA that is not present in the 160 mm objective:

lca-1.png
lca-2.png

Those must be ca free objectives then ! Forget about those overpriced Nikon CF and CFI posers. Grab some Carlsan objectives while you still can !

[EYE C U]

I see now, this just made me realize I can deny it no longer..... I'm blind as a Bat.

IT'S LIKE PEOPLE THAT BUY A 4K TV...MOST PEOPLE CAN'T EVEN TELL THE DIFFERENCE UNLESS THEY WEAR THEIR BEST GLASSES

[hans]

Those must be ca free objectives then ! Forget about those overpriced Nikon CF and CFI posers. Grab some Carlsan objectives while you still can !

Well based on the first image using the Carlsan stand the objective itself appears to at least be more "CF" than the final image from the Microstar IV. However I looked back at some of my test images and the color is in the wrong direction to be explained by the doublet alone, so perhaps the change in working distance is having a larger effect?