Schneider 28mm f2.8 Componon Perf Stacked is Extremely Good

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Lou Jost
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Post by Lou Jost »

To Robert's list of perfectly flat field lenses, I would add the Printing Nikons and all photolithography lenses (such as Ultra-Micro-Nikkors and Zeiss monochrome S-planars).

RobertOToole
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Post by RobertOToole »

JohnyM wrote:
lothman wrote:thanks for sharing if I only could understand why adding another lens with numbers of additional lens can improve thing so much?
Suprizingly, like many others, Schneider enlarging lenses are optimized for infinity, despite being enlarging. Also effective aperture is improved quite a bit.
I think this is right or something close to it. Most of these, like the 2.8/28 here has a spec of 1/20 magnification optimization thats not very close.

An optical designer that comments on DPreview sometime ago posted that all lenses made, even a 1x macro lens, are designed at infinity and only much later in the manufacturing process do they tune the design for a closer distance. So they are based on infinity performance first and foremost.

Robert

ChrisR
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Post by ChrisR »

has a spec of -lowish- magnification optimization thats not very close.
That always seemed to be an easy assumption.
What I don't understand, is why some lenses designed for close work seem to be above average as "tube" lenses.
Chris R

Lou Jost
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Post by Lou Jost »

Robert, even if that guy on DPreview is right, that's just the starting point of the design, and the lens design could go through so much transformation during the design process that it could even be unusable at infinity (as in the Repro-Nikkors). Normally, macro lenses are really optimized for a specific target magnification and aren't necessarily good at infinity. But a magnification of 1:20, which is 0.05, is very close to zero, so that is close to infinity-optimized.

Lou Jost
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Post by Lou Jost »

Chris, I think one criterion is flatness of field of both lenses, so that they play nice together. And macro/enlarger lenses tend to have flatter fields than regular lenses.

RobertOToole
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Post by RobertOToole »

Lou Jost wrote:Robert, even if that guy on DPreview is right, that's just the starting point of the design, and the lens design could go through so much transformation during the design process that it could even be unusable at infinity (as in the Repro-Nikkors). Normally, macro lenses are really optimized for a specific target magnification and aren't necessarily good at infinity. But a magnification of 1:20, which is 0.05, is very close to zero, so that is close to infinity-optimized.
I agree. Sorry if my reply wasn't that clear.

By these lenses performing much better stacked at a certain magnification than focused at the same magnification by extension mean they are operating closer to the designed optimization range stacked?

Consumer Macro lenses have to perform at infinity and closer distances but I don't think any are optimized for 1x.

Being good in the range of 1:20 to 1:5 with a range down to 1x is different than a special lens made for 1x only.

What gets me is why a rear lens optimized for 0.75x is so clean and sharp at infinity when used in a stack. My two best tube lenses are both made for 0.75x :shock:

Best,

Robert

SebastianFg
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Post by SebastianFg »

Hello Robert,
I have an Rodagon D 120 f5.6 APO ( optimized at 1:1) and used it as rear lens with my Componon 50 f2.8 (not tested at infinity yet, pushed further than infinity). I can’t comment about the quality because I don’t have another option to try (apart from my Raynox 250, which is bad), but what I saw so far looked very promising. Soon I will couple a 28 mm f2.8 rodagon (never saw one and don’t find any infos about it, only f4) to it and test it, first handheld try looked promising. But maybe the apo rodagon rear lens would be interesting for you to test it.
Best regards,
Sebastian
Last edited by SebastianFg on Sun Dec 30, 2018 6:06 am, edited 1 time in total.

ChrisR
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Post by ChrisR »

Has anyone - (Robert this will be you if anyone!) - tried reversing a lens like a 105 macro lens, to try it as the longer lens?
It should be bad, but who knows!
Chris R

Davids
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Post by Davids »

Robert - I apologize if you have already discussed this in other posts, but is the goal to get the stacked lenses as close as possible or is a certain distance between front elements necessary?

Thanks

RobertOToole
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Post by RobertOToole »

SebastianFg wrote:Hello Robert,
I have an Rodagon D 120 f5.6 APO ( optimized at 1:1) and used it as rear lens with my Componon 50 f2.8 (not tested at infinity yet, pushed further than infinity). I can’t comment about the quality because I don’t have another option to try (apart from my Raynox 250, which is bad), but what I saw so far looked very promising. Soon I will couple a 28 mm f2.8 rodagon (never saw one and don’t find any infos about it, only f4) to it and test it, first handheld try looked promising. But maybe the apo rodagon rear lens would be interesting for you to test it.
Best regards,
Sebastian
Hi Sebastian,

I have thought about the Rodagon 120 D before but I don't see these for sale very often.

The 2.8/28 Rodagon should be excellent stacked. Years ago I did test the Rodagon 2.8/28, Rodagon 4/28, Componon against the Componon 28s, and a Canon MP35 all on extension at 2x (the center was a close call between all 4 but in the corners it was no contest against the MP35).

Rodenstock was always very quiet about the f2.8 version, I have only seen it listed for sale one time and my copy was the only one I have ever seen.

Let us know what you find with the Rodagon D 120 and the 2.8/28 Rodagon when you are testing.

Thanks for the tips.

Best,

Robert

RobertOToole
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Post by RobertOToole »

Davids wrote:Robert - I apologize if you have already discussed this in other posts, but is the goal to get the stacked lenses as close as possible or is a certain distance between front elements necessary?

Thanks
Good question, I think as close as possible is best. Some lenses, like the lomo 3,7 isn't affected much, but almost all the others seem to perform best very close.

As a general rule I try to get them almost touching. I like to mount both stacked lenses inside a threaded 52mm (Thorlabs SM2) so I can place them very close without thread adapters getting in the way.

Also it can help to move the aperture to the space between the lenses (thanks Lou!) Some show less CAs with the aperture in the factory position, some are better with it moved using a paper disk. Others like the Componon 2.8/28 are very good a f/2.8 and best at f3.15, so there is not much difference either way it seems.

Best,

Robert

dmillard
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Post by dmillard »

SebastianFg wrote: I have an Rodagon D 120 f5.6 APO ( optimized at 1:1)
Hello Sebastian,

I previously had a copy of this lens. The Apo-Rodagon D 120mm f/5.6 is optimized for duplication at a 2:1 ration when used in the forward orientation, and at 1:2 when reversed. The lens would perform best as a taking lens at 1:2 magnification when used forwards. I looked for the relevant Rodenstock documents, but they are buried somewhere, so B&H came to the rescue:

https://www.bhphotovideo.com/c/product/ ... gon_D.html

The analog Apo Macro Sironar 120mm f/5.6, which appears to have a similar optical design, also has its peak performance at 1:2 :

Image

Best regards,
David

p.s. Good luck with your tests! I look forward to seeing your results.

SebastianFg
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Post by SebastianFg »

Hello David,
Thank you for the information.
This lens is surprisingly not very common,so far I am really happy with it.

Hello Robert,
From time to time one comes in German eBay up for sale (right now one).
I will test it (it takes a few days) and post the results here.
Thank you so far with your work, it inspired a lot of people (me included) so far.
Best regards,
Sebastian

ray_parkhurst
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Post by ray_parkhurst »

Looks like that "Apo" lens will have some strong red hues when focused 200um high.

soldevilla
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Post by soldevilla »

Hi. What is the optical design of your assembly, Robert?
Macro Symmar is focusing to infinity and then you superimpose the Componon? It is assumed that an enlarger lens works best when the distance to the focus from the front and back is short ...
I already have some tests to do next year.

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