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Pentakta 2.8/30
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PostPosted: Sun Aug 07, 2022 10:23 pm    Post subject: Pentakta 2.8/30 Reply with quote




test
Pentakta 2.8/30 + Sony NEX C3
Aperture improved => really 1/2


PostPosted: Mon Aug 08, 2022 7:06 am    Post subject: Reply with quote

Yep, this indeed is an overlooked "sleeper" mini projection lens from a Zeiss Jena microfiche system - I have it and use it since many years.
https://www.flickr.com/photos/kds315/albums/72157672267931183

My hometown Weinheim:


Amazing 3D-pop it has:


I recommend to make/use a sunshade for it, as contrast in your images seems to be low - not a lens fault, it handles it very well Wink



I don't think tampering with the aperture to open it up wider than the anyway fast f2.8 it is made to, isn't really a successful idea - lost sharpness + contrast obviously.
Zeiss usually knew rather well what they were doing Wink


PostPosted: Mon Aug 08, 2022 8:41 am    Post subject: Reply with quote

kds315* wrote:
Yep, this indeed is an overlooked "sleeper" mini projection lens from a Zeiss Jena microfiche system - I have it and use it since many years.
https://www.flickr.com/photos/kds315/albums/72157672267931183

I recommend to make/use a sunshade for it, as contrast in your images seems to be low - not a lens fault, it handles it very well Wink

I don't think tampering with the aperture to open it up wider than the anyway fast f2.8 it is made to, isn't really a successful idea - lost sharpness + contrast obviously.
Zeiss usually knew rather well what they were doing Wink


Beautiful shots and an interesting lens! I assume it doesn't have a mount?

There must be quite a few of these small overlooked lenses out there. I recently found a Dokumar 25mm f/8 (which I've seen you have as well) and while I knew about most of the other Dokumars (and like them a lot) this one was completely new to me.


PostPosted: Mon Aug 08, 2022 9:23 am    Post subject: Reply with quote

Yep, it is just a tube lens, no mount at all, so some clamp mount I have made and using a M42 focusing helicoid. Does only cover micro 4/3 format at infinity, full format at close-up.

Here a few images (link only as they are not my images...):
https://www.worthpoint.com/worthopedia/pentakta-30mm-f2-vintage-lens-mistery-405670304

The lens is just pressed into that plastic housing; I removed that and had a metal clamp made to mount it.

Btw there are a few other focal lengths and speeds, but rare to find. That 2.8/30mm is quite common - and cheap.


PostPosted: Mon Aug 08, 2022 9:29 am    Post subject: Reply with quote

simple.joy wrote:


Beautiful shots and an interesting lens! I assume it doesn't have a mount?

There must be quite a few of these small overlooked lenses out there. I recently found a Dokumar 25mm f/8 (which I've seen you have as well) and while I knew about most of the other Dokumars (and like them a lot) this one was completely new to me.


Here a bit about the DOKUMAR lenses, quite some sleepers too they are:
https://radojuva.com/en/2021/03/carl-zeiss-jena-dokumar-8-38/

I have six (6) DOKUMAR lenses listed on my site macrolenses.de http://www.macrolenses.de/objektive.php?lang

Yours should be this one: http://www.macrolenses.de/ml_detail.php?ObjektiveNr=188



PostPosted: Mon Aug 08, 2022 12:33 pm    Post subject: Reply with quote

Thank you very much for all the information. As I’m sure you know, Marco Cavina also wrote an excellent article comparing the 47 mm version to the S-Biogon 40 mm (http://www.marcocavina.com/articoli_fotografici/Zeiss_cute_DFR_DDR_lenses/00_pag_English.htm).

My favorite is the 38 mm f/5.6 though. Would love to try some of the f2.8 ones but they don’t seem common and I assume the image circle might be pretty limited as well.


PostPosted: Mon Aug 08, 2022 12:38 pm    Post subject: Reply with quote

simple.joy wrote:
Thank you very much for all the information. As I’m sure you know, Marco Cavina also wrote an excellent article comparing the 47 mm version to the S-Biogon 40 mm (http://www.marcocavina.com/articoli_fotografici/Zeiss_cute_DFR_DDR_lenses/00_pag_English.htm).

My favorite is the 38 mm f/5.6 though. Would love to try some of the f2.8 ones but they don’t seem common and I assume the image circle might be pretty limited as well.


Marco is a long time good friend of mine and we share / exchange all information about lenses Wink


PostPosted: Tue Aug 09, 2022 12:17 am    Post subject: Reply with quote

kds315* wrote:
I don't think tampering with the aperture to open it up wider than the anyway fast f2.8 it is made to, isn't really a successful idea - lost sharpness + contrast obviously.
Almost any lens at an open aperture is less sharp than at a 1-stop covered one, however, everyone likes to use the fastest lenses across the entire aperture range, including at an open aperture, guided by a specific scene. Here is an interesting review on this lens:
https://radojuva.com/2020/09/pentakta-2-8-2-30-with-sony-e/
“The Pentakta lives up to its mission and shows excellent sharpness in the center of the frame already at f / 2. Of course, the result deteriorates towards the edges of the frame due to the coma characteristic of planar lenses. Vignetting is present in the F / 2-F / 2.8 range. The best image quality (across the field) on an APS-C sensor is achieved at F/5.6-F/8.
The contrast of the formed image in normal lighting conditions is very good, with hard backlight it decreases, purple reflections appear. In general, light resistance can be assessed as very good for a single-coated lens.
The recognizable but unobtrusive Pentakta bokeh is reminiscent of Tevidonovskoe - this lens is also a perfectly corrected planar. Circles of confusion have an almost uniform distribution of brightness, closer to the edge of the frame, due to vignetting, they turn into characteristic "lemons" - almost symmetrical due to the slight influence of coma (unlike, for example, Helios)."

Also on this site you can see examples of photos from it. For universal application, you need to set an adjustable aperture from ½ to 1/8, this is expensive, I settled on the option without aperture, since my goal was to get a compact 1/2 portrait lens with good bokeh and soft pattern with natural color reproduction and contrast, and not cartoon picture). For architecture and macro, I have other lenses with aperture adjustment. For architecture on Pentakta, it makes sense to set the aperture to 1/8 to achieve maximum sharpness, as recommended by "radojuva". In your architecture example,
kds315* wrote:

My hometown Weinheim:


you can see that the right side of the image is unsharp at 1/2.8 - it would be better at 1/8, then there would be enough depth of field.

kds315* wrote:

Zeiss usually knew rather well what they were doing Wink
Yes, they made a special lens for a narrow task - Pentakta 2.8 / 30 is a microfiche lens from the Pentakta L100 projection device, which was manufactured by VEB Pentacon in the GDR. Since sharpness and aperture were needed, apparently they reached a compromise by calculating the optical design for an open aperture of ½ and covering it by 1 step.


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I added some cartoonishness settings). But visually, the original photos were the closest to the original real picture, looked at several ordinary uncalibrated monitors.
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https://sony-club.ru/forum/threads/pentakta-30-2-8-30-2-0.70609/
More examples of modifications.