Lomo 1.7X projective photoeyepiece

[Duke]

I had the virtually same problems with my Nikon SMZ-10 trinocular, as I so used to direct projection, I've tried everything I could and came to conclusion that it was impossible.
It has 0.6x reduction in the phototube and image is deep inside the tube.
So I've started to read about how this adapters even work. I've ended up with buying (for ~5$) LOMO Projection eyepiece 1.67x originally used in MFN-10 photoattachment (resulting magnification is 0.6 * 1.67x = 1x, what I was going for), it is designed to use with full frame cameras like ZENIT-C. Since all technical information about LOMO's equipment is fully disclosed in the literature (optical schematics, aberration calculation, etc.), I was able to figure out the base principals, and I think I know how all of this projection eyepieces work, and how to design custom one (in terms of magnification and LCA compensation) using only just a regular eyepiece and achromatic lens.
If this information is helpful, let me know, I'll post it here or maybe in separate topic.

ADMIN NOTE: this thread was split from "DSLR adaptation to Nikon AZ100 38mm Photoport" viewtopic.php?f=25&t=42470

[Pau]

Thanks Duke.

I didn't know about the existence of the Lomo 1.67X projective It can be a a very desirable part to adapt APSC cameras to microscopes. Is it corrective? Have you already tested it?

I was able to get good coverage and parfocality with direct projection on the Canon over the SMZ1000 photoport

On the other hand, 1X doesn't seem adequate for APSC with the AZ100 because the good image circle is pretty small, in particular at low zoom settings, a PLI 2.5X seems to match better
2.5 x 0.6 = 1.5X seems adequate, the eyepieces have a FN 22mm and work at 1X; 22 x 1.5 = 33mm, sufficient for 26.82mm Canon APSC diagonal but still wider subject field than with the 2/3" sensor camera and 0.6X tube alone.

[viktor j nilsson]

Is this the one you are referring too?
https://www.ebay.com/itm/Lomo-microscop ... SwOyNew~Hv

I have a 3x homal eyepiece in a drawer, but never tried it out. Didn't know they made a 1.67x. Would be interesting to try. I was under the impression that the Homal eyepieces weren't designed to be used in the same way as other projection eyepieces (like Nikon CF PL and Olympus NFK), but never looked into it.

[Duke]

Is this the one you are referring too?
https://www.ebay.com/itm/Lomo-microscop ... SwOyNew~Hv

I have a 3x homal eyepiece in a drawer, but never tried it out. Didn't know they made a 1.67x. Would be interesting to try. I was under the impression that the Homal eyepieces weren't designed to be used in the same way as other projection eyepieces (like Nikon CF PL and Olympus NFK), but never looked into it.

Yes, that's it. It has 1.7x printed on it, but it's an approximation, the precise value of magnification is 1.66(6)x. There are different types of homals for different types of photoattachments, yours is for format film, not for FF compact cameras. Homals are negative optical systems with LCA compensation, while this projection eyepiece is not anything like it.
LOMO 1.67x intended use is for low power achromats, such as 3.7x/0.10, 8x/0.20, 20x/0.40 and others. It doesn't feature any sort of LCA compensation according to the books, the main aberration suppose to be "mild" astigmatism on the corners of full frame camera.
I haven't tried it yet, at the moment, finalizing my setup. Maybe next week.
However, other people tested it, reported the image quality was "good". How good exactly, I'll have to test myself.

[dolmadis]

I didn't know about the existence of the Lomo 1.67X projective It can be a a very desirable part to adapt APSC cameras to microscopes. Is it corrective? Have you already tested it?

Disappointing to note but the top of the Lomo 1.7x Homal will not sit into the mount of a BH2 Trino.

Best

John

[Pau]

John, this is normal: the BH2 tube has a very tight space to accommodate the NFK photoeyepiece that has a very small shoulder, an older BH or CH tube has not this restriction (like many other models from several brands)
Anyway, if you use the BH as intended with Olympus LB objectives you need NFK compensating photoeyepieces

[Duke]

dolmadis Again, Lomo Projection Eyepiece 1.67x is not by any means homal. It's Huygens eyepiece 4x with F.N. of 24mm paired with spheric singlet of F=103mm placed in it's exit pupil, which is used to project image on 100mm above the outlet flange of the eyepiece.
So. I've done tests. It can in fact cover the FF (light circle is about 42mm), but even on APS-C (Sony Nex-5 SD 28.12mm) image quality is unbearable.
SMZ-10T zoom at 1x (1.5x with vertical illuminator) + LOMO PE 1.67x Photoport

SMZ-10T zoom at 1x (1.5x with vertical illuminator) + Nikon CFUW 10x/26.5 (photo through the eyepiece using Canon SX40)

SMZ-10T zoom at 4x (6x with vertical illuminator) + LOMO PE 1.67x Photoport

SMZ-10T zoom at 4x (6x with vertical illuminator) + Nikon CFUW 10x/26.5 (photo through the eyepiece using Canon SX40)

Well, I've had my hopes up for it, but thinking logically, it's what you should expect, keeping in mind what it is. Huygens eyepieces is already the worst eyepiece, which doesn't feature any sort of aberration correction, paired with single lens, which makes image even worse. I was thinking and hoping for, that LOMO might be using some special type of glass and this lens might be aspheric element to some how fix Huygens eyepiece aberration, but it's not.
It is what it is. Waste of my 5$.

[viktor j nilsson]

Thanks for testing that! Sorry it didn't work out, but valuable information for us all.

[dolmadis]

Thanks for then test Duke. Disappointing. Your $5 could have been $45 for me and others on a punt.

BR

John

[Duke]

Well, anyway, I've had a backup plan. And then, another backup plan .
Before I even considered LOMO PE 1.67x, the first option was to get AmScope DSLR adapter 2x or it's Chinese counterpart NDPL-1(2x), it's relatively cheap (~90$) and easy to adapt.
The tests of such adapters was on prc68.com site long time ago, now it's unreachable. Did someone try them out?
Final option is Nikon CF PL 2x. It's not cheap by all means, and rare as hen's teeth. But what can you do, gotta sometimes break a piggy box for a something rare and good, before it became priceless...

[viktor j nilsson]

I personally don't think that paying the going rate for a 2x CF PL is a good investment as full frame cameras are becoming so affordable. Personally, I would rather get a 2.5x CF PL, use your 7D with some cropping for now, and get a FF camera when you find a good deal. I recently found the best deal (free) on a 5D mark II which is still a great camera.

If I were to buy a 2x, however, I might be tempted to pick one up from niyong1987-5. I've just bought several Olympus short-barrel objectives from him, and they have been excellent, fairly priced and very well packaged.

[Scarodactyl]

The ndpl generic 2x adapters are good in some contexts, particularly bausch and lomb stereos. I haven't done a proper test on a nikon but I have a vague memory of getting a bad result on an smz-10.

[Pau]

Duke,
In a former post you said that the Lomo 1.7 projective is meant to be used with low magnification objectives not needing compensating eyepieces, but the lateral chromatic aberration shown at the Lomo 1.7 images seems typical of compensating eyepieces used with objectives that don't need it, likely a relevant test will be with a Lomo (high magnification) or Zeiss objective needing that correction. The fuzziness at the center, more present in the first image seems worse...

[Duke]

Pau,
It was a translated citation from the instructions of MFN-10. There's 3 projection systems in the kit of MFN 10x photoattachment:
1. Projection eyepiece 1.67x (To use in conjunction with low magnification achromatic objectives)
2. Homal-1 (To use in conjunction with medium to high magnification achromatic objectives, low magnification apochromatic objectives)
3. Homal-2 (To use with high magnification apochromatic objectives)
Just from the fact, that LOMO PE 1.67x is Huygens eyepiece, you should know it has no "correction" whatsoever, it's totally uncorrected in terms of optical aberrations.
It introduces spherical aberration, coma, field curvature, distortion, astigmatism, lateral and axial chromatic aberrations to the resulting image.
From pure fact, that curved optical surfaces are faced the intermediate image plane, and flat surfaces are faced to resulting image plane, you can view this system as "inverted objective", thus means it has negative lateral chromatic aberration and negative field curvature, so there is some compensation of those going on resulting image, but spherical aberration, coma, astigmatism, etc. introduced to the image is on much larger scale. This is exactly what is evident on the 1 photo, the fuzziness comes from spherical aberration, coma, astigmatism, and worsen by the fact that its optical elements uncoated, and blacking is poor. The first image made with lower zoom factor, at the maximum of effective aperture and resolution, it uses whole aperture of the projection eyepiece, while at 4x it's only used partially, thus minimizing geometric aberrations, while making chromatic more evident.
BTW, Sorry for hijacking your thread.

[Scarodactyl]

I have two of these coming in from Russia, and the seller mentioned one was an older uncoated version and one was a newer coated one. So who knows, maybe that has varied over time. They were cheap so it's fine either way.