50X objective recommendation

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jnh
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50X objective recommendation

Post by jnh »

Recently, a friend of mine made me aware of micrometeorites. Their size distribution peaks around 300 um, so a 50X lens would be nice to have for imaging these.
I have a 20X Mitu, which is sometimes challenging to use, so 50X would be even more so. Hence, I wouldn't want to go all out on the 50X Mitu, and it's way too expensive anyway (even used), so I was wondering, if there is a 50X with decent NA (>0.6) and working distance (maybe more than a mm), that could be generally recommended and costs - say - less than $500?
Last edited by jnh on Sun Jan 03, 2021 3:33 pm, edited 1 time in total.

Scarodactyl
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Re: 50X objective recommendation

Post by Scarodactyl »

What do you find difficult about the 20x?
The 50x mitutoyo is definitely expensive, and aside from the super long working distance and parfocality its lower reaolution isn't ideal for photography anyway. You might find an Olympus umplanfl or lmplanfl or mplanfl 50x, they are occasionally inexpensive and give a great image. Less than 1mm working distance but oblique lighting is still possible.

jnh
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Re: 50X objective recommendation

Post by jnh »

Beyond 10X things get quite a bit more challenging, I find. Lighting is one thing, and while my rig is fairly sturdy, it just sits on a desk and at 20X anyone walking around in the house or a car/truck driving by outside messes things up. Also, I have a WeMacro controller with a motorized linear stage that has very similar specs to the WeMacro rail. The 1 um (or slightly below) stepping required for 50X is very much at the borderline of the what the rail/controller can handle.
Thanks for pointing out the Olympus objectives. I noticed those on eBay and was wondering, if the 50X offerings were any good, but the short working distance concerned me a little.

Scarodactyl
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Re: 50X objective recommendation

Post by Scarodactyl »

Vibration issues will only be worse at 50x if 20x is a problem. You might want to consider getting a heftier stand like a measurescope base or something like sorbothane for vibrational isolation. Having done 20x shots with a wobbly base I'd definitely recommend it as a quality of life improvement. We all have enough stress in our lives right now.

Lou Jost
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Re: 50X objective recommendation

Post by Lou Jost »

When you arrive at higher magnifications that challenge the rail's step size, whether now with these micro-meteorites or sometime in the future, I highly recommend buying a WeMacro MicroMate and letting it drive the fine-focus knob of your microscope. This gives you an order of magnitude smaller step size than the rail, and is more stable. I recommend it very highly; I already have two and am waiting for a chance to buy another. They have almost completely weaned me away from rails.

Adalbert
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Re: 50X objective recommendation

Post by Adalbert »

Hello,

Yes, for the high magnifications you need small steps.
I usually take 3 photos per DOF, but for high magnifications more than 3.

BTW, what about the Mitutoyo M 50 / 0.65 ?
https://www.photomacrography.net/forum/ ... o+bargains

Best,
ADi

jnh
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Re: 50X objective recommendation

Post by jnh »

Earlier this year I started lowering my step size significantly below the DOF of the objective, which made a bit of an improvement. But I have yet to try multiple images per step.
Thanks for pointing out that M50/0.65 Mitutoyo, wasn't aware of that one. There's currently one on eBay - quite the bargain indeed.

Chris S.
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Re: 50X objective recommendation

Post by Chris S. »

Adalbert wrote:
Mon Jan 04, 2021 5:37 am
BTW, what about the Mitutoyo M 50 / 0.65?
https://www.photomacrography.net/forum/ ... o+bargains
The Mitutoyo M Plan 50x/0.65 objectives I've seen are optimized for NIR or UV, not VIS. While these objectives certainly cover portions of the VIS spectrum reasonably well, I'm not sure I'd choose one if imaging with visible light were the intended task--while they are often less expensive than similar VIS objectives, the ones I've seen still cost a fair amount of money.

Or have I missed a VIS model?

--Chris S.

Scarodactyl
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Re: 50X objective recommendation

Post by Scarodactyl »

This is an obscure objective which may not have been made by mitutoyo themselves (sometimes also labelled asahi I think?) Off of a hardness tester.

Lou Jost
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Re: 50X objective recommendation

Post by Lou Jost »

Remember that for infinity-correced objectives, the NA matters more than the rated magnification. A 40x with an NA of 0.65 will give you just as much resolution at 50x as a 50x 0.65 objective. You just need to use a longer tube lens. This gives you more options. You might even want to consider the super-cheap $100 nikon 20x 0.70 which, when pushed to 50x, will outresolve any of the Mitutoyo 50x models under discussion here.

pierre
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Re: 50X objective recommendation

Post by pierre »

I have a Nikon 50x NA 0.8 LU PLAN EPI with WD 1mm if interested.
Regards

Pierre

Adalbert
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Re: 50X objective recommendation

Post by Adalbert »

Hello Chris,

The name of this Mitu is M 50 and not M Plan 50.

- first side:
Mitutoyo
JAPAN
1205001


- second side:
M 50
0.65 / ∞
810 – 619


It is located in the middle of the following picture:
3x50.jpg
Best,
ADi

jnh
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Location: US East Coast

Re: 50X objective recommendation

Post by jnh »

Thanks everyone for the input so far. I bought the M50 on eBay - figured, can't go wrong for $100 plus change. Will see how it works out...

Medwar
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Re: 50X objective recommendation

Post by Medwar »

Adalbert,
could you please post here the WDs of M 50 0.65 and Olympus NA 0.8?

Adalbert
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Re: 50X objective recommendation

Post by Adalbert »

ca. 1mm

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