Lomo 1.7X projective photoeyepiece

[Pau]

...
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.

Thanks for the complementary info, now it's much clearer.
In fact I'm not strong in Optics theory and much less on Lomo equipment. You must be right but the scheme of the Lomo 1.7 shows two separated eye lenses so it is a modified huygenian design.
It happens that I own an old unbranded huygenian type eyepiece only labeled "Compens 10X" that effectively is compensating, showing the typical orange peripheral halo (and tested). It came with an old Zeiss industrial microscope part.

BTW, Sorry for hijacking your thread.

No problem, this is very usual.
Just for clarity and ease to find, because both subjects are enough different and interesting I've split the thread.

[Ichthyophthirius]

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...

I don't have this stereo microscope so I can only comment on this from the manual https://lavinia.as.arizona.edu/~mtuell/ ... Manual.pdf

It seems that the photoport can receive the 1x TV lens. The Nikon MDC lens could then be put on the C-mount and the camera would be adapted with a camera lens.

Another theoretical option could be to use the Nikon CF PL 2.5x in combination with a 0.7x focal reducer to reduce the image down for an APS-C sensor. Apart from my own attept I haven't seen any tests of this idea lately. I'm wondering if no-one has tried or if it doesn't work.

Regards, Ichty

[Scarodactyl]

The 1x tv lens is not much use outside of a pretty limited context, since it only has a 16mm image circle. The MDC lens is meant for adapting on a coolpix camera without an interchangeable lens, at that point you might as well just go afocal with a good viewing eyepiece.
I think a focal reducer has a lot of potential but I'm not sure how you'd design one.

side-note but my lomos just came in this afternoon. They look identical except that one has an obviously coated front element and the other does not. I need to print another 42mm to m42 adapter for my optiphot and then I'll run some tests.

[Ichthyophthirius]

I think a focal reducer has a lot of potential but I'm not sure how you'd design one.

I previously used an old enlarger lens which worked quite well. But for this, I'm particularly thinking of a 0.7x focal reducer (Speedbooster; Lens Turbo etc.) I even bought one recently to test for this purpose but I haven't come around to it yet.

[Duke]

As I'm impatient to make my SMZ-10 setup work ASAP, I've decided to test something else.
As a matter, I don't like particularly complicated designs that use excessive number of elements, I like to keep things as simple as possible, adding each piece of glass gives me an internal struggle. Projective systems, as good as they are, most of the time only make image worse. I mean on old compensation system, it was necessary evil, but on the CF you really don't need them.
What I've decided to do is to add simple negative apochromatic triplet (Barlow lens 2x), to extend the image from the tube and add magnification.
I'll see how it works.

[Scarodactyl]

Just got my lomo 1.7xes in, one coated one uncoated, and thought I'd do a quick/bad comparison between them, a nikon 2.5x pl and an olympus nfk 2.5x, all on my optiphot with the eyepieces in the same trinocular port. The nfk needs to sit a lot lower than the nikon (the nikon is also much longer), and the camera had to sit lower still over the lomos.
Unfortunately I apparently bumped the wafer between shots, but the signal is strong enough that the measurement doesn't need to be very precise. Shot with a Nikon BD 20x on my canon t6.
Nikon PL 2.5x

center:

corner:

Not really great but it's not an apo objective or anything. There might still be a coating on this wafer too, I should be using the really really nice one from macro_cosmos but whatever.
Olympus NFK 2.5x:

center:

corner:

Just as you'd expect the center is about equivalent, but the compensations in the corners add a fair amount of lateral CA and probably some spherical distortions as well.
Lomo 1.7x without coating:



And with coating (at least one surface on the front lens is coated, though the back lens does not seem to be):



So.........yeah. not exactly disastrous at the very, very center but everywhere else it's pretty darned bad, like it's missing some element. Olympus NFKs do pretty mild compensations vs zeiss of this era (weakest vs strongest of the mainstream makers) but nothing this extreme--I know an olympus nfk 2.5x can be used on a zeiss universal without major issues. I don't want to just conclude that these are just terribl....at least they do give 1.7x mag?

Basically Duke is right about everything--wish I saw his note before I bought these, though at least they were cheap.

Still, it's hard to imagine any context where this performance would have been considered acceptable, even with Lomo's somewhat dodgy reputation for consistent quality.

[viktor j nilsson]

Really nice to see your tests, Duke and Scarodactyl. A little surprised that the NFK worked quite OK with the Nikon BD. I guess a FF sensor would be more revealing, though.

Contrast seems pretty low overall, is that an effect of epi illumination or maybe the wafer coating?

One comparison I'd love to see is one between a Nikon 2x CF PL and a CF PL 2.5x with a decent reducing lens (0.8x or 0.6x). It doesn't seem like a lot of people use reducing optics with Nikon CF gear, but they do seem to work fine in Wild/Leica setups? I'm not sure how you would construct such a setup and how the spacing needs to be. Have you, Scarodactyl?

[Scarodactyl]

It had fairly low contrast in the eyepieces as well. Just had another look and I picked a pretty ugly part of the chip for this. coaxial illumination does tend to wash some things out.
Given how bad the corners were doing with the NFK on aps-c I imagine on FF it would be really bad.
On the wild/leitz/leica setups they're not really reducing lenses, it's a fully afocal setup, so you have a normal viewing eyepiece focusing the image to infinity and then a camera lens focused to infinity putting it on the sensor. That isn't an ideal option on Nikons or Olympus because their viewing eyepieces aren't as well corrected as their photo eyepieces. Maybe if you put a 40/50mm pancake over a nikon/olympus photo eyepiece and focused it appropriately it would just work, I haven't tried it. If I were going to do this seriously on a nikon for myself (and I might at some point) I'd probably use one of the Chinese 10x/22 23.2mm eyepieces in the trinoc port since some brief testing suggested they had better color correction than Nikon cfns plus a wider FOV. On a Nikon compound and some stereos direct projection is the best solution, but not always possible as in the smz-10, at least without some drastic and perhaps improbable modifications.

[Scarodactyl]

https://www.ebay.com/itm/402320510838
I just came across this listing for a full set. There are some lenses in the adapter, and I wonder if they are essential for image quality.

[viktor j nilsson]

https://www.ebay.com/itm/402320510838
I just came across this listing for a full set. There are some lenses in the adapter, and I wonder if they are essential for image quality.

Yup, there's the 3x eyepiece I have but never figured out how to use. (The Lomo water immersion phase objective I got at the same time turned out to be delaminated and I never really liked phase contrast anyway, so I never spent much time trying to figure it out).

If Duke or anyone else has a schematic that shows how the different Homal pieces were meant to be used, I'd be interested to see it!