Microscope Eyepieces WF10X /22mm Diopter-adjustable High Eye

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Saul
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Microscope Eyepieces WF10X /22mm Diopter-adjustable High Eye

Post by Saul »


Ichthyophthirius
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Post by Ichthyophthirius »

Hi,

No, but I think an FN22 is impossible for a 10x eyepiece like this for 23.2 mm tube diameter.

Regards, Ichty

Scarodactyl
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Post by Scarodactyl »

Seems unlikely. Not that expensive even for Chinese eyepieces too. I'll admit to being a bit curious, not buy it curious but curious.

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Post by ray_parkhurst »

Ichthyophthirius wrote:Hi,

No, but I think an FN22 is impossible for a 10x eyepiece like this for 23.2 mm tube diameter.

Regards, Ichty
I have 23.2mm B&L "WF 22" and "WF 23" eyepieces, so from spec perspective 22 and even 23mm is possible. I have not actually measured them however. I also have 15x which have 20mm FN in 23.2mm mount. All of these have glass at the very end of the 23.2mm tube. The 15x are essentially solid glass with some airspaces from one end to the other!

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Post by rjlittlefield »

ray_parkhurst wrote:All of these have glass at the very end of the 23.2mm tube.
That's an important observation. With glass at that point, the eyepiece can intercept light that would have made a 22 mm or 23 mm field at the standard focus plane, and redirect it as necessary to stay within the clear space of the eyepiece barrel.

--Rik

Ichthyophthirius
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Post by Ichthyophthirius »

ray_parkhurst wrote: I have 23.2mm B&L "WF 22" and "WF 23" eyepieces, so from spec perspective 22 and even 23mm is possible.
Hi,

That's very interesting, thank you. I've never come across these. Do they look like this? https://www.ebay.com/itm/Bausch-amp-Lom ... 3080101057

All the European microscope eyepieces have a maximum FN20, made possible by a field lens right at the lower end of the eyepiece, too. A few low-magnification projection eyepieces have FN 22 but then the field lens is several cm down the microscope tube.

The Chinese eyepiece doesn't seem to have a field lens like that - it'll be interesting if it can actually go up to FN22.

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Post by rjlittlefield »

I have a couple of these https://www.ebay.com/itm/223222148146 , nominally "WF10X/20" with 23.2 mm barrel.

Image

They actually deliver a little more than FN 20, and there's no glass anywhere near the tip of eyepiece barrel. In fact the glass doesn't start until about 12 mm above the end of the microscope tube, way up in that wide section of the eyepiece.

There's no magic needed for this. The walls of the eyepiece are pretty thin, leaving about 21.2 mm inside the barrel, and the field stop is just a minor narrowing down to a hair over 20 mm.

With some extra glass near the end of the barrel, down inside the microscope tube, I have no trouble believing FN22 or FN23.

--Rik

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Post by Saul »

Looks like the same item on ebay
https://www.ebay.com/itm/252525114990

ray_parkhurst
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Post by ray_parkhurst »

Ichthyophthirius wrote:
ray_parkhurst wrote: I have 23.2mm B&L "WF 22" and "WF 23" eyepieces, so from spec perspective 22 and even 23mm is possible.
Hi,

That's very interesting, thank you. I've never come across these. Do they look like this? https://www.ebay.com/itm/Bausch-amp-Lom ... 3080101057

All the European microscope eyepieces have a maximum FN20, made possible by a field lens right at the lower end of the eyepiece, too. A few low-magnification projection eyepieces have FN 22 but then the field lens is several cm down the microscope tube.

The Chinese eyepiece doesn't seem to have a field lens like that - it'll be interesting if it can actually go up to FN22.
Yes, I think those are the same. I'll take some pics of mine if you like.

As I remember, the WF23 have really long 23.2mm tubes, so long in fact that I don't think they work on some of the B&L stereo pods. The end of the barrel hits the glass window at bottom of the tube.

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Post by ray_parkhurst »

I pulled out my box of eyepieces to verify, and I am glad I did! Turns out the WF22 have super long tubes and glass at end of barrel, and while the WF23 have longer barrels than my other eyepieces, they have no glass.

Here are the measured FNs for a few of my B&L (and other) eyepieces:

5x (old): 20mm
WF23: 18.5mm
WF22: 18mm
10xWF Lab: 18mm
10xWF (aluminum 80's vintage): 21mm
10x WF stereo (black aluminum 80's): 20mm
15x Ultra Widefield: 19.5mm
AO 10x 145: 20mm
Nikon CFW10x: 18mm

The narrow FN of the WF22 and WF23 are disappointing. I've seen eBay sellers tout the extra wide field of these, and indeed they've sold for a big premium over the normal ones.

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Post by rjlittlefield »

ray_parkhurst wrote:WF23: 18.5mm
WF22: 18mm
...
The narrow FN of the WF22 and WF23 are disappointing.
It's also very puzzling. This is like a lens manufacturer advertising 220 or 230 mm focal length, but actually delivering 180 or 185. In both cases the measurement is simple enough to check that I would expect users to be howling up a storm about the mislabeling.

For my eyepieces the measurement was easy to check two ways, first by calipers across the field stop, and separately by imaging a stage micrometer through a 10X objective. Here's a cell phone pic:

Image

I assume your measurements were done with stage micrometer?

--Rik

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Post by ray_parkhurst »

rjlittlefield wrote: I assume your measurements were done with stage micrometer?
Rik...I just used a ruler on the stage to measure the FOV with 1x pod magnification.

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Post by rjlittlefield »

ray_parkhurst wrote:
rjlittlefield wrote: I assume your measurements were done with stage micrometer?
Rik...I just used a ruler on the stage to measure the FOV with 1x pod magnification.
That sounds equivalent. Did you test all your eyepieces the same way, on the same scope?

--Rik

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Post by ray_parkhurst »

rjlittlefield wrote:That sounds equivalent. Did you test all your eyepieces the same way, on the same scope?
Yes, all same method and scope pod.

Edited to add: this was actually a good exercise. I had been using a favorite pair of eyepieces for a while, and with these measurements I found out why they were my favorite pair: they were the pair which measured 21mm, and were sharp to the edges. I ended up going through all my eyepieces and found that some older B&L had 20mm FN while others had 21mm. The 21mm tend to be sharper and with flatter field as well. Needless to say I have now segregated them and found a good backup pair. Interestingly, these are not from the same era, one pair being from late 60's vintage, the other from early 80's. Not sure why there is such a difference, but perhaps B&L had multiple formulas, or maybe different subcontractors?

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Post by Scarodactyl »

Interesting results!

That said, I'm surprised the 15x uwf wouldn't be the constant choice, even with the lower field number. I feel like I'm looking through a straw with anything else now.

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