finite lenses working as infinite lenses

[soldevilla]

Yes, it sounds like heresy, but everything has to be tested before denying the possibility that it works. The first test has been placing my cheap x4 (very cheap, some day I must to change it) in front of the Rodenstock 180. I really like the result.



Now I am printing an adapter for M39, to see how well the enlarger lenses work, at low magnification.

To be continue...

[Scarodactyl]

It's actually not too surprising at lower magnifications--the lomo 3.7x actually works even better on a tube lens. I do like the results, and I'm curious how they compare to it on empty extension.
That said, look at your corners--you're getting classic stars showing coma/astigmatism creeping in.
3d printers are a rela gamechanger for adapters. I hope you'll keep sharing your results!

[soldevilla]

I don't care much about those corners, I can't expect too much from a 5€ x4 lens. Like I said, I need a new objective ...

[Scarodactyl]

I mention them not as a criticism of the lens or image, but as a potential consequence of going infinite. Just something to be aware of when deciding how to configure it. Did the center get better vs finite usage?

[Macrero]

Very few finite objectives I tried worked well used as "infinity". The Lomo 3.7 works brilliantly, the Lomo 4/0.12 does well with a tube/rear lens as well. Other Lomo's didn't work well. The Nikon U10/0.22 is another good one. Curiously the U5 and U20 didn't work well in infinty configuration, but they do not work very well as finite either.

Anyway, I always try any possible configuration before I give up on a lens/objective, despite what theory says.

Most enlarging/industrial lenses do benefit from a rear lens in stacked configuration. The main benefit is improved coverage, but also overall IQ. Scanner lenses do not generally work well stacked. At least none of the scanner lenses I tried did well with a rear lens.

This is one of the fun parts of photomacrography. You never know how some lenses will perform on camera till you try, unless someone have already tried and reported... In theory, sometimes there is a difference between theory and practice

- Macrero

[jurkovicovic]

I have a similar experience with finite objectives. In some cases, a tubelens can improve finite objective.
Here: Rodagon 150mm f5,6 removed partially chromatic aberration and improved the image circle.
https://www.zonerama.com/jurkovicovic/P ... /266541941
https://www.zonerama.com/jurkovicovic/P ... /266539055
Here: without Rodagon
https://www.zonerama.com/jurkovicovic/P ... /266537940

[soldevilla]

Test with a enlarger lens Nikon 50 in front of the Rodenstock 180... Hum, I feel it is not the best image, I need to test and compare without tube lens

[soldevilla]

In the other extreme, this is a image with the x40 Nikon and the Rodagon. Only 0.65mm FOV. Not too happy with it, but I not sure if the culprit is the x40, the tube lens or the photographer

[Macrero]

Test with a enlarger lens Nikon 50 in front of the Rodenstock 180... Hum, I feel it is not the best image, I need to test and compare without tube lens

Was the El-Nikkor reversed? Try with different rear lens/es. No need for a stellar lens. Even a close-up triplets (Raynox) or some doublets (Sigma LSA) works very well as rear lenses in combos. In my tests the difference between the Raynox 250 and the Makro-Symmar 120 used as rear lenses was pretty trivial.

Or try the same combo at different magnification/s.

It's all about trial and error...