Question about this eBay item.

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fibreoptix
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Question about this eBay item.

#1 Post by fibreoptix » Sat Jul 21, 2018 2:35 am

I recently purchased a used Nikon Labophot. I'm trying to achieve dark field but with no luck. I'm new to this stuff. I found this on eBay just now.

Nikon Microscope Phase Contrast 2 1.25 Field Condenser
https://www.ebay.ca/itm/323202029733?Vi ... 3202029733

It's a phase contrast condenser with Dark and Bright field. I do not have PC objectives......yet. Right now I just want to start with DF.

Will the dark field with this condenser still work? If it does, I know it would only work until 40x....or maybe I'm wrong about that.

Attached are the objectives I have.

Thanks
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Hobbyst46
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Re: Question about this eBay item.

#2 Post by Hobbyst46 » Sat Jul 21, 2018 8:45 am

In general, darkfield is used with the same objectives as for brightfield - apart from high numerical aperture objectives (NA>~0.8).

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fibreoptix
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Re: Question about this eBay item.

#3 Post by fibreoptix » Sat Jul 21, 2018 1:49 pm

So this condenser is 1.25. What does that mean?

Hobbyst46
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Re: Question about this eBay item.

#4 Post by Hobbyst46 » Sat Jul 21, 2018 2:12 pm

fibreoptix wrote:So this condenser is 1.25. What does that mean?
It means that the NA of the condenser is 1.25 PROVIDED that there is a layer of immersion oil between the top lens of the condenser and the underside of the slide. Otherwise, if used dry, the NA of the condenser is lower - depends on the model and should be printed in the instruction manual. This condenser, using the immersion, can provide brightfield illumination with the 100x objective. IF it performs similar to the Zeiss condenser (as I would guess - but no guarantee), it may provide nice darkfield with your 40x as well (not with your 100x), PROVIDED there is oil between the top lens and the slide.

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fibreoptix
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Re: Question about this eBay item.

#5 Post by fibreoptix » Sat Jul 21, 2018 4:16 pm

So i need to find a condenser that has a na>.8 for dry veiwing. Damn. Oh well thought this would have done the trick. The stuggle continues. Thanks for the info.

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Re: Question about this eBay item.

#6 Post by PeteM » Sat Jul 21, 2018 4:51 pm

The Nikon phase condenser you show will work for darkfield up to 40x (400x total power with a 10x eyepiece) without oiling the condenser. As Hobbyist notes, it won't work at 100x, but it's OK with a 40x plan achro.

I happen to have a couple Labophots, one with that same phase condenser, and a variety of Nikon 40x plan lenses (one like yours but silver body, a CF and a Fluor version). The 40x Fluor (which has an astounding numerical aperture of 1.3) doesn't work with the darkfield stop - but the others do. You can also get some interesting oblique effects with all the achros (.7 NA and under), by offsetting some of the other phase annuli.

That said, if you plan on getting phase contrast, you'll likely save money by looking for a Nikon phase scope, complete with phase lenses and the trinocular head you want. Keep the best parts -- and there still should be a very nice second Labophot to sell.

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fibreoptix
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Re: Question about this eBay item.

#7 Post by fibreoptix » Sat Jul 21, 2018 5:55 pm

Thats some good advice. For the subject matter im interested in, pond water organisms, i think an inverted scope would suit my needs more.

Its the filiming of these creatures that gets me excited as well as observing them. Which adds a whole new layer of complexity and cost. Im also learning about DIC now.

Hobbies, gotta love the rabbit hole they create.

photomicro
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Re: Question about this eBay item.

#8 Post by photomicro » Sat Jul 21, 2018 6:17 pm

I have a condenser like this, only it just says 'Phase contrast' so I assume is version 1.

It has a dark-ground position, marked 'D' as well as the bright-field position 'O' (with iris diaphragm) in addition to the Ph1, 2, 3 and 4 rings that match x10, 20, 40 and 100 objectives respectively.

It is often the case that one of the phase rings gives good dark-ground with an objective.

To get high power dark-field you need to oil the condenser, but also, it is limited to objectives of NA less than unity, ie. 1, anyway.

To see more, change to x15 eyepieces with a good x40.

If you fancied a go at phase with such a condenser, I have some spare DL phase objectives, a x10, x40 and x100. PM me if interested.

You may find this website useful'

https://lavinia.as.arizona.edu/~mtuell/ ... _list.html

Hope this helps.

Mike

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Re: Question about this eBay item.

#9 Post by Hobbyst46 » Sat Jul 21, 2018 7:35 pm

@photomicro
I see that Nikon made four sizes of phase rings. Does it mean that a Nikon microscope, per a given magnification, would yield better (more accurate) phase contrast than a Zeiss microscope, say, where the condenser only features three sizes? because the Nikon condenser phase stops match the Nikon phase objective ring sizes better than the corresponding match on the Zeiss ? I hope that is not a dumb question...

photomicro
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Re: Question about this eBay item.

#10 Post by photomicro » Sun Jul 22, 2018 10:19 am

Hobbyst46 wrote:@photomicro
I see that Nikon made four sizes of phase rings. Does it mean that a Nikon microscope, per a given magnification, would yield better (more accurate) phase contrast than a Zeiss microscope, say, where the condenser only features three sizes? because the Nikon condenser phase stops match the Nikon phase objective ring sizes better than the corresponding match on the Zeiss ? I hope that is not a dumb question...
I do not think that this is necessarily so, but am happy to be corrected.

I am guessing that it may be to do with the design of the optics, and it could be that Nikon decided to do this because of the optical design of their CF objectives.

Also, as the angle of acceptance is higher with increasing NA (and hence magnification) so the annulus in the condenser has to be bigger. On the other hand, the optical design of the condenser could also dictate this.

Interestingly, with the Zeiss(West) system from the 1960s onwards, the Ph2 and Ph3 settings are for objectives from the x16 to the x100, with the less commonly seen Ph1 only for the x6.3 and x10.

Baker, and others, made a system where the phase plate in the condenser was a cross shape, and hence only the one did for all objectives (just using more or less of each of the four 'arms')

Mike

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Re: Question about this eBay item.

#11 Post by Hobbyst46 » Sun Jul 22, 2018 10:40 am

Thanks Mike!
My Zeiss condenser indeed is a Ph2, Ph3, DF, BF, not Ph1. I use the 16x, 25x, 40x (Ph2), 63x and 100x (Ph3).

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