How about Pentacon lenses?

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soldevilla
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How about Pentacon lenses?

Post by soldevilla »

Anyone here know how work as tube lens the Pentacon 200 f4 telephoto lenses? I have seen some in the markets of Leipzig, where I am working now

enricosavazzi
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Re: How about Pentacon lenses?

Post by enricosavazzi »

soldevilla wrote:
Mon Nov 08, 2021 10:12 am
Anyone here know how work as tube lens the Pentacon 200 f4 telephoto lenses? I have seen some in the markets of Leipzig, where I am working now
I have not tried, but judging from eBay these lenses are quite common and are available in several types of barrel, so it is quite possible that optical formulas, lens coatings and actual makers have changed through the years. What applies to one specific model used as a tube lens might not necessarily apply to other models. Prices on eBay are very variable, but probably you should not be willing to pay more than 20-30 € even if in reasonably good condition.
--ES

soldevilla
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Re: How about Pentacon lenses?

Post by soldevilla »

My idea with this lens is to use it as a tube lens, but I want to try to put a pap motor that drives the focus ring and use that for the photo shifts for stacking. I have no idea if this can work, but it is cheap to test and if it works the set will be very rigid, as it does not need a displacement guide.

lothman
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Re: How about Pentacon lenses?

Post by lothman »

soldevilla wrote:
Sat Nov 13, 2021 3:04 am
..., but it is cheap to test and if it works the set will be very rigid, as it does not need a displacement guide.
I think the focus barrel will have a good amount of wobble, so the attached microscope lens will wobble too. So I don't expect such a setup as "very rigid" but worth a try.

Lou Jost
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Re: How about Pentacon lenses?

Post by Lou Jost »

This works very well for me with tube lenses that have internal motors, but the focus range of most lenses is too shallow to cover a deep stack, especially at high m (m>5). A macro lens, with its much longer focus throw, does best. Even then, you will be limited to low m and/or very flat subjects.

ray_parkhurst
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Re: How about Pentacon lenses?

Post by ray_parkhurst »

Do infinite objectives perform well when the tube lens is focused far from infinity?

Lou Jost
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Re: How about Pentacon lenses?

Post by Lou Jost »

That's idiosyncratic, appears to depend on tube lens and objective. One needs to test. I have mostly used this technique with MFT lenses, used with high-end front optics (Apo-Xenon, Mitu) as a lightweight field stacking option.

ray_parkhurst
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Re: How about Pentacon lenses?

Post by ray_parkhurst »

Lou Jost wrote:
Sat Nov 13, 2021 6:58 am
That's idiosyncratic, appears to depend on tube lens and objective. One needs to test. I have mostly used this technique with MFT lenses, used with high-end front optics (Apo-Xenon, Mitu) as a lightweight field stacking option.
I can see this perhaps working better for stacked lenses as you are using them than for optimized infinite objectives such as the Mitutoyos.

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Re: How about Pentacon lenses?

Post by rjlittlefield »

ray_parkhurst wrote:
Sat Nov 13, 2021 6:37 am
Do infinite objectives perform well when the tube lens is focused far from infinity?
It works well at low NA and shallow stacks, less well at higher NA and deeper.

See viewtopic.php?t=14569 for some of my experience, 10X NA 0.25 at the top of the thread, then 50X NA 0.55 at bottom of first page.

--Rik

soldevilla
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Re: How about Pentacon lenses?

Post by soldevilla »

wow, how many responses! This morning it was just a crazy idea jumping through my few brain cells. Now I'm looking on ebay for one of these targets. Although I will try to wait for the Leipzip Flohmarkt, if they don't confine us first.

soldevilla
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Re: How about Pentacon lenses?

Post by soldevilla »

While I eagerly await the Pentacon, I have made an impromptu test. Since I don't have my collection of adapters here, I have placed a x4 on a stand and lowered the camera with the 100 macro until it almost touched the x4 adapter. In this way, the microscope objective and the camera objective are not in contact and vibrations are not transmitted. I check that the distance between macro 100 and x4 is not critical, I have plenty of distance to move it before the vignetting appears. It has spherical aberration, but it is possibly because I am using the only objective I have here and it is a finite lens. But (and this is what I wanted to try) I can move the focus of the 100 macro with my hand to focus the different planes and the image does not move at all on the accessory screen that I have connected to the camera.
This afternoon I try to send a photo

soldevilla
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Re: How about Pentacon lenses?

Post by soldevilla »

Here the photo with the phone
Attachments
FOTO2.jpg

soldevilla
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Re: How about Pentacon lenses?

Post by soldevilla »

At home, I have been able to test the 200 Pentacon after printing the appropriate thread adapter. Not a bad lens, but I have a certain feeling that the 180 Rodenstock that I am using normally. I think the old Pentacon has a bit more chromatic aberration around the edges. Since I only have an infinity microscope objective and it is now easy to print new adapters, I am testing my finite objectives using them as infinity, in front of the Rodenstock180. And the result is nothing bad. I will open a new thread to show this

The example is a Montgomerite, with a field of 2.2mm

Image

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