A few years ago I picked up a Lomo 7x. It's marked for luminescence work ("Л"), but there's no tube length or cover slip correction noted.
When I got it, I put it on a Zetopan and could not get it focus. It looked too old to be an infinity objective, but I didn't pursue the matter further.
Today I put the thing on a Vanox AH I have been working on, just for kicks. Turns out that the working distance for this objective is enormous, far outside the range of what the Zetopan can handle, but within the range of the Vanox AH. Quality seems OK. It's no Leitz 6.3x Fluotar, but it's OK.
I believe it was part of the Lomo Federov stage arrangement, which allows positioning of a petrographic sample in three dimensions - hence the need for a very long working distance. Anyone know for sure?
With the very long working distance, perhaps it might be OK for macro work? Any other thoughts on how to use the thing? Looking for gemstone inclusions maybe?
Lomo 7x 0.17 w/ Iris -- Information, please?
Re: Lomo 7x 0.17 w/ Iris -- Information, please?
Federov stage Is what I am guessing too; I have seen and owned many common LOMO objectives. Don’t know for sure.
As you know, Federov objectives use that ball lens as part of their optical system, so without it, they may not perform the best. At NA 0.17, it may still work well for macro; I am not just not sure how well.
The common LOMO 8x and 9x short barrel biological objectives are pretty good and cheap though (some plan 9x versions have iris too and have good working distance); they should work better for macro.
As you know, Federov objectives use that ball lens as part of their optical system, so without it, they may not perform the best. At NA 0.17, it may still work well for macro; I am not just not sure how well.
The common LOMO 8x and 9x short barrel biological objectives are pretty good and cheap though (some plan 9x versions have iris too and have good working distance); they should work better for macro.
Re: Lomo 7x 0.17 w/ Iris -- Information, please?
It's not clear to me that the glass hemispheres participate in image making - at least I don't think they are part of the objective's design optical formula. I think they are essentially neutral. I think the idea is that the sample (a thin section slide) gets mated to the hemispheres with glycerin such that when you tilt the slide in the universal mount, the light path does not deviate at the air-slide junctions in a variable degree depending on the slide angle. In other words, the hemispheres ensure that the light to goes straight into objective without being bent. I think that's why there are several different type of hemispheres with different refractive indexes in the kit, to match either glass or sample?
The 9x with iris is a pretty good objective. It doesn't have nearly the working distance this 7x does, though. This 7x really falls apart when stopped down very far at all.
The 9x with iris is a pretty good objective. It doesn't have nearly the working distance this 7x does, though. This 7x really falls apart when stopped down very far at all.