Looking for a 20x 160/210 objective recommendation

[Will Milne]

Hi

Seems like the rabbit hole has me in it's grip:)

If you were buying a 20x - 160/210 tube length objective for transmitted light work , direct to cam sensor/ microscope setup , what would you consider. Budget is sub $300.

Will

[Charles Krebs]

Will,

You'll need to provide a little more info about subject matter and lighting.

If you will be working strictly with transmitted light, then working distance does not really matter much. If you want to use "top-lighting" then it does.

Will your subjects be covered with a cover-glass? When you get to 20X you start encountering numerical apertures where you want to pay attention to the cover requirements. If the subjects will not be cover-slipped then you will want an "M" type objective designed for no cover slip. Something like the Nikon CF M Plan (the 210mm finite version). There were at least three versions... a "regular" working distance, a LWD, and an ELWD.

If the subject will be mounted with a cover slip you will want an objective designed for this. This is going to be a tougher one to find, because most finite (160mm tube length) 20X objectives used eyepiece color compensation so they are not the greatest for "direct projection" purposes. The exception was once again the Nikon CF series objectives. But the 20X ones don't seem to show up too often.

[seta666]

I bought a 20x Nikon M Plan 210/0.40 LWD (WD 6mm) for 200$ + 18$ shipping with the intention of using it on bellows. I think that 6mm is fair enough for lighting. I was looking for a bd 210/0.4 ELWD but I found only 2 of them over 500$ and one was quite beaten up.
I do not have it yet, as soon as I recieve it I will make some tests
Regards

[enricosavazzi]

I don't quite remember the price of my M Plan 20x 210/0 ELWD, but probably it was not much more or much less than 300 $. It did take some time for one to come up on the bay (one or two years ago).

[seta666]

The member bklein bought an M plan 20x 210/0.40 LWD for 110$ few weeks ago, I paid a bit more. I was looking for the ELWD but seems difficult
Regards

[Will Milne]

Hi

Realize now I should have been less vague. I need the lens to do transmitted bright/dark/oblique lighting. Lighting is sub-stage flash and subject matter is bog/fen/wetland zooplankton imaged in water with coverslip.

Working distance is not an issue.

If 20x is problematic to find I am wondering how much of an effect shortening the tube length on a 160 or 210 tube length 40x would have on CA and resolution , with an eye to reducing the magnification close to the range I am looking for. My 10x is simply not enough to get the framing I would like- to much dead space with the subject matter.

Will

[Charles Krebs]

If 20x is problematic to find I am wondering how much of an effect shortening the tube length on a 160 or 210 tube length 40x would have on CA and resolution

Nope, not a good idea. Not only will you get image quality grief from the improper tube length, you are reducing the "coverage" and may not even get an acceptable image circle to cover an APS sized sensor.

For some reason used 10X and 40X "biological" objectives (cover slip) are everywhere, but 20X are less common. Doesn't mean they are impossible to find, and I would just keep an eye out (for Nikon CF's). Except for the Plan Apos they should be within your budget.

[Will Milne]

Thanks Charles- I was hoping but alas:)

I just had a chance to try a Nikon 20/0.4 160/0.17 ( unmarked as to E or Plan ) a friend had on her Labophot. Seemed sharp enough but still more CA than I would like in bright and oblique - bright flash lighting. None of the software I have Capture NX/Picture Window Pro/PS CS4 seem to be able to reduce it to acceptable levels, I'm guessing it's radial CA and not transverse .

The search continues....

Will

[seta666]

Thanks Charles- I was hoping but alas:)

I just had a chance to try a Nikon 20/0.4 160/0.17 ( unmarked as to E or Plan ) a friend had on her Labophot. Seemed sharp enough but still more CA than I would like in bright and oblique - bright flash lighting. None of the software I have Capture NX/Picture Window Pro/PS CS4 seem to be able to reduce it to acceptable levels, I'm guessing it's radial CA and not transverse .

The search continues....

Will

My E plan 10x 160/0.25 has horrible Purple/yellow CAs, specially with bright backgrounds and black hairs. If the background is neutral and the subject has not black hairs CAs are not a problem any more
Regards

[Will Milne]

Thanks to a heads up on a Fleabay BiN from a thoughtfull forum member, I managed to snag both the 20/0.5 160/0.17 and 40/0.7/160/0.17 Nikon CF Plan's for under my orginal budget.





Thanks for the guidance and help all:))

Will