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Tiger Beetle (2)
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mjkzz



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PostPosted: Mon Jun 18, 2018 11:39 pm    Post subject: Tiger Beetle (2) Reply with quote

After shooting with Laowa, restacked it using El-Nikkor 50mm reversed with Pentax 105mm as tube lens. It is not that bad for this 50 dollar lens.





Sony A7III in full electronic mode
Mid-Curtain Flash Triggered by controller
El-Nikkor 50mm
Pentax 105mm SMC as tube lens
MJKZZ Ultra Rail
91 Images at 60um Step Size
Zerene Stacker
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Beatsy



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PostPosted: Tue Jun 19, 2018 12:01 am    Post subject: Reply with quote

Nice result. Really good detail in the crop. Is that as good as you're used to seeing from your El-Nikor on other tube lenses? (I didn't know Nikors worked on tube lenses actually).

As a slightly related aside: I've never used or owned a Nikkor, but someone at my camera club asked if a "Nikon lens from an enlarger"was any use to me as he's throwing out some old darkroom stuff. He didn't know the FL but, on questioning, did remember it had "Nikkor", not "Nikon" on it. He's bringing it to the club Thursday (and refuses to take anything for it). Excited! Never rains but it pours... Smile
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Macrero



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PostPosted: Tue Jun 19, 2018 3:02 am    Post subject: Reply with quote

Nice stacks.

"Relay lens" would be a more correct term for the Pentax in this case. Stacking/coupling lenses is an old, well-known technique and it often works better than a single reversed lens. I found that coupling the Componon 28 and 35 (among other lenses) with 100+ FL relay lenses improves resolution and especially coverage.

- Macrero
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Beatsy



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PostPosted: Tue Jun 19, 2018 3:10 am    Post subject: Reply with quote

Macrero wrote:
Nice stacks.

"Relay lens" would be a more correct term for the Pentax in this case. Stacking/coupling lenses is an old, well-known technique and it often works better than a single reversed lens. I found that coupling the Componon 28 and 35 (among other lenses) with 100+ FL relay lenses improves resolution and especially coverage.

- Macrero

Ahhh - lightbulb moment! I'll add relay lenses my reading/research list. Suspect that's what I'm doing with my Linoscan lens (but called the lens behind it a tube lens - till now). Thanks for that.
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Macrero



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PostPosted: Tue Jun 19, 2018 3:34 am    Post subject: Reply with quote

Beatsy wrote:
Ahhh - lightbulb moment! I'll add relay lenses my reading/research list. Suspect that's what I'm doing with my Linoscan lens (but called the lens behind it a tube lens - till now). Thanks for that.


Result cannot be predicted, it would depend on various factors, but it's worth trying, for sure.

Johan Ingles has a write-up about coupled lenses on his site:

http://extreme-macro.co.uk/coupled-reverse-lens/

- Macrero
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mjkzz



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PostPosted: Tue Jun 19, 2018 5:22 am    Post subject: Reply with quote

Oh, OK. I think others might call my configuration as "stacked", or "coupled" lens. To me a stacked configuration is nothing but a front lens + a tube lens (to extend optical tube).

I always thought a tube lens is one form of relay lens.

@Beatsy, you are so lucky to get those lenses free Very Happy Mine is El-Nikkor 50mm, an enlarging lens. I found one Rayfact enlarging lens, looks identical to this one, but I was told it is better as it is an "industrial" lens.
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Lou Jost



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PostPosted: Tue Jun 19, 2018 5:32 am    Post subject: Reply with quote

I'm very fond of coupled lenses and have posted some examples in various spots on this forum. Even just common, cheap lenses sometimes work well. Best if the lenses are both good at infinity, but as Rik said somewhere, a lens optimized for 25x (for example) is optimized for m=0.04, which is pretty close to 0 (m=0 would be infinity).

It is usually helpful to put a paper stop between the lenses, preferably at the front focal plane of the reversed lens, which makes the system telecentric as an added bonus.
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mjkzz



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PostPosted: Tue Jun 19, 2018 5:43 am    Post subject: Reply with quote

Lou Jost wrote:
I'm very fond of coupled lenses and have posted some examples in various spots on this forum. Even just common, cheap lenses sometimes work well. Best if the lenses are both good at infinity, but as Rik said somewhere, a lens optimized for 25x (for example) is optimized for m=0.04, which is pretty close to 0 (m=0 would be infinity).

It is usually helpful to put a paper stop between the lenses, preferably at the front focal plane of the reversed lens, which makes the system telecentric as an added bonus.


Yeah, I have read some of your posts about it. I remember you even tried to couple two identical lenses together to get superb 1:1 magnification. Be honest to you, inspired by your posts, I am trying to do the similar setup as you did before Very Happy

I tried to put this El-Nikkor 50mm on Raynox 150 to get 4.16x, but the result is not very good. So I guess these lenses are good at lower mag, say less than 2x. So I am looking for an 85mm lens to be the tube (or relay, or back lens).
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Lou Jost



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PostPosted: Tue Jun 19, 2018 5:47 am    Post subject: Reply with quote

Don't forget to use a paper aperture rather than the apertures of the lenses themselves, unless the front lens has a much shorter focal length than the rear lens, in which case you may be able to use the front lens aperture.
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mjkzz



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PostPosted: Tue Jun 19, 2018 7:09 am    Post subject: Reply with quote

Macrero wrote:
Nice stacks.

"Relay lens" would be a more correct term for the Pentax in this case. Stacking/coupling lenses is an old, well-known technique and it often works better than a single reversed lens. I found that coupling the Componon 28 and 35 (among other lenses) with 100+ FL relay lenses improves resolution and especially coverage.

- Macrero


Come to think of it more, I believe the Pentax 105mm is more like a tube lens than a relay lens. The El-Nikkor 50mm is fixed focus to infinity and the Pentax 105 is set to focus to infinity. The El-Nikkor, to me, is just another infinity corrected objective, and since it is reversed, it is beaming "parallel" ray to the Pentax 105mm which in turn, converge the "parallel" rays and projects an image on the sensor, exact meaning of a tube lens.

On the other hand, the semantics of relay lens is broader, after googling, I think it refers to a lens that takes an image plane and project it to yet another image plane (hence relay) MORE than a tube lens (which deals with light rays instead of image plane).

Maybe we can define a tube lens as those that deals with light rays (infinity corrected or not) and relay lens as those that deals with projecting image plane to yet another. Otherwise, it is really confusing to talk about them.
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Lou Jost



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PostPosted: Tue Jun 19, 2018 7:12 am    Post subject: Reply with quote

Yes, the 105mm is acting as a tube lens, but the EL-Nikkor is not infinity-corrected. But it's close enough.
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mjkzz



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PostPosted: Wed Jun 20, 2018 3:16 am    Post subject: Reply with quote

Lou Jost wrote:
Yes, the 105mm is acting as a tube lens, but the EL-Nikkor is not infinity-corrected. But it's close enough.


Thanks, learn something new, my optical knowledge is very limited. I will google up what exactly an infinity corrected lens is (when it is reversed).
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mawyatt



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PostPosted: Wed Jun 20, 2018 5:19 am    Post subject: Reply with quote

Lou, Peter,

In Peter's lens scenario with the 105mm being close to a "tube" lens, would this configuration benefit from a paper aperture between the two lenses?


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mawyatt



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PostPosted: Wed Jun 20, 2018 5:25 am    Post subject: Reply with quote

Peter,

This looks pretty good with the EL-Nikkor 50mm & Pentax 105mm as a "tube or "relay" whatever this ends up being called. I got caught using the tube/relay terms awhile back Embarassed

Now I've got to find my old EL-Nikkor somewhere and give this a try someday.

Certain old lenses never die Shocked

Thanks for posting.

Best,
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Lou Jost



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PostPosted: Wed Jun 20, 2018 6:02 am    Post subject: Reply with quote

Mike, the EL should be stopped down one or two stops to be really sharp, but it's hard to say whether the best place to do that is in the lens or behind it. When the tube lens is much longer than the front lens, then the front lens' aperture is often usable. When the two lenses are similar in focal length, the paper aperture is almost always best. This is an intermediate case, so an empirical test would be worthwhile.

Rik has pointed out elsewhere that the default should be to stop down a combination somewhere between the two lenses.

Theoretically the combination can be made telecentric with the right choice of aperture position.
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