Nikon Dark field stop on ebay. Anyone familiar with these?

[fibreoptix]

Trying to get my ABBE 1.25 labophot condenser to achieve dark field. There is no info on diameter or compatible condensers.
Anyone here ever try them?

https://www.ebay.ca/itm/NIKON-X2-DF-DAR ... %7Ciid%3A1

This is my condenser

[PeteM]

Looks to me like the Ebay auction if for the turret type ("Zernicke") Nikon phase condensers, not yours. In any case, the price is way too high.

If you're handy, you might try to make a somewhat flexy wide hole stopper to fit into the bottom of your condenser and try cutting out various black vinyl stops. Maybe something like a plastic bottle cap of the right OD, with most of the top cut off. Place them just a bit below the condenser iris. There's also an Ebay seller who will sell a set of what look to be laser cut vinyl darkfield stops in various diameters. You should be able to mock up darkfield to at least 200x and maybe 400x at next to zero cost.

Nikon made a phase condenser -- for the Alphaphot series I think and similarly for the E100 series -- that took a two position slider. This looks somewhat similar to yours (and it will fit with the same dovetail) but with space for a slider to go through it. This is a good "chassis" for experimenting with both phase and darkfield stops; allowing you slide a darkfield stop across the field. These are also in the proper position -- just a bit above the condenser iris.

On edit, one example: https://www.opticsplanet.com/nikon-e200 ... 73100.html

Another example:

Labophot06s.jpg (31.35 KiB) Viewed 5962 times

The other option, pricier, is a proper Nikon Labophot/Optiphot phase condenser with all the annuli for phase and darkfield in a turret configuration. However, just that Ebay bit of plastic at $100 is priced higher than the former condenser (if you find one) and near half the cost of the turret type (maybe $250).

[fibreoptix]

Thanks so much for taking the time. Yes I've been told the same by the person who sold me the scope. Place a stop below the iris. I've tried and tried various diameters stoppers which result in either black or light light grey which doesn't look like dark field at all.

I somewhat stopped because of phase contrast (PC) though. I ultimately would like PC and saw these condensers which already have a dark field position on the annuli (dial?). I believe this is what you are referring to in your 3rd option offering.



So since I want to go get a PC set up I think this might be the best option? Thoughts?

[PeteM]

Yes, a proper phase condenser as shown would be good. You'll also need Nikon phase lenses for the phase contrast.

[apochronaut]

You may already be familiar with this. http://www.science-info.net/docs/Nikon/ ... -phase.PDF

[fibreoptix]

You may already be familiar with this. http://www.science-info.net/docs/Nikon/ ... -phase.PDF

OMG I was literally just looking for that. Thank you so much.

[carlh6902]

This was in Microbehunter issue #54:


Edit 4/14/2019: Replaced outdated link with a link to the master index, which always contains the most recent versions:

https://drive.google.com/open?id=0B7ckZ ... nFYVDJSRW8

Carl

[fibreoptix]

This was in Microbehunter issue #54:

https://drive.google.com/open?id=1PMLL1 ... aP9MC7zOwe

Carl

Yes I've seen that. I did not have any luck. I went with the Contrast adapter anyway since I want to make it a phase contrast scope. Best of both worlds.

[apochronaut]

I have and have used both the carousel type of phase condenser as well as the slideway type. Both give equally good results, as long as the condenser itself is equivalent but the cumbersome routine of having to slide individual phase sliders in and out of the condenser, very quickly becomes bothersome. Additionally, one has to find multiple sliders for a condenser, which more often than not was sold with only one.
Typically, those type of condensers were mfg. for applications where only one magnification with phase was needed, and the slider could be quickly engaged and disengaged, when needed or not. Some of the cheaper Chinese phase systems employ such a mechanism for all phase magnifications. If you are going to use phase a fair amount, getting a phase carousel type condenser or even opting for a universal type, with DIC prisms as well, might be the way to go, if you are planning on adding DIC later on.

Regarding adapting a DF stop to a condenser, phase or not : phase condensers are a little different than some BF condensers in that they must be designed so that the front focal plane of the condenser is at the location of the phase annuli(us). This is a rather short focal distance, in most cases. A DF stop placed in the same location as the annuli, will be considerably larger than even the annulus for the 100X objective. In looking at such an arrangement for the Labophot condenser, and without having exact measurements, the .90 DF stop looks to be just slightly less than 1/2 the diameter of the .90 phase3 annulus and is located in the same plane. In making a stop for a standard BF condenser, it would be advisable to place it as close to the front focal plane of the condenser as possible, or as close to the iris diaphragm as possible, to obtain a precise annular circle. An out of focus or diffuse annular circle will progressively destruct the precision of the DF effect, with the degree of distance from the focal plane and as well alter the required diameter required to get DF at all. If the filter slot or carrier in the condenser is not right adjacent to the iris diaphragm, it might be difficult using such a device to carry a DF stop.