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Carl Zeiss Jena 25mm/1.4 Biotar adapted to M4/3
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PostPosted: Fri Apr 16, 2021 6:50 pm    Post subject: Carl Zeiss Jena 25mm/1.4 Biotar adapted to M4/3 Reply with quote
Hi All,

This is a topic on request: http://forum.mflenses.com/posting,mode,quote,p,1550238.html

Yesterday I took delivery of a Carl Zeiss Jena 25mm f1.4 Biotar lens that originally had a pentaflex 16 mount. The eBay seller modifies these to M4/3 mount. This intrigued me so I decided to pick one up. The serial number dates it to 1962-ish.

So yes, it does have some hard vignetting in the corners since the lens is intended for a 16mm movie camera and a M4/3 sensor is 21.6) mm across. No amount of stopping down resolves that. But I think it also means that the lens is actually wider than 25mm (about 18.5 by my math?), so room to crop down.

The lens has also been serviced and regreased. Smooth as silk. The first thing I tried was one of my standard sharpness and contrast tests where I take a series of pictures of a building about 750 meters away with apertures from wide open to usually about f11. My initial impression is that even wide open at 1.4 it is sharp with fairly decent contrast. Stop it down 1 stop and contrast improves considerably. I am really impressed.

First picture shows the lens on my E-M5 Mk.II (taken with an E-M1 Mk.II and an OM 50mm 3.5 macro).
Second pic shows the vignetting. The frame of that picture is 85.5 wide, I was about 3 meters away.






Regards, C.


PostPosted: Fri Apr 16, 2021 9:13 pm    Post subject: Reply with quote
if you go for the 1.4/50mm then there is no vignetting anymore, but is a bit more costly.
I have both and actually 2x of the 50mm, as it is sooo good!

Last edited by kds315* on Tue Apr 23, 2024 9:25 am; edited 1 time in total


PostPosted: Fri Apr 16, 2021 11:04 pm    Post subject: Reply with quote
kds315* wrote:
if you go for the 1.4/50mm then there is no vignetting anymore, but is a bit more costly.
I have both and actually 2x of the 50mm, as it is sooo good!


How do you adapt these lenses? I mean, I have one so I know it can be done. But when searching eBay for Pentaflex 16 to MFT (or variations thereof) it turns up nothing.

Regards, C.


PostPosted: Fri Apr 16, 2021 11:37 pm    Post subject: Reply with quote
connloyalist wrote:
How do you adapt these lenses? I mean, I have one so I know it can be done. But when searching eBay for Pentaflex 16 to MFT (or variations thereof) it turns up nothing.
I found this item - https://www.ebay.com.au/itm/Pentaflex-AK16-lens-to-Micro-4-3-adapter-Olympus-OM-D-Lumix-GH5-Blackmagic-BMPCC/193870350438

I do like your adapter. Looks very neat with the OMD and the lens

Like 1 small


PostPosted: Mon Apr 19, 2021 2:03 pm    Post subject: Reply with quote
kds315* wrote:
if you go for the 1.4/50mm then there is no vignetting anymore, but is a bit more costly.
I have both and actually 2x of the 50mm, as it is sooo good!

My sample of the 1.4/50 mm Biotar was nowhere as good as the 1.4/25 mm. The latter is very sharp, even wide open. You have to crop the dark corners or use it after sunset, but I would prefer it over my 1.4/50 mm.


PostPosted: Tue Apr 23, 2024 9:22 am    Post subject: Reply with quote
kds315* wrote:
if you go for the 1.4/50mm then there is no vignetting anymore, but a bit more costly.
I have both and actually 2x of the 50mm, as it is sooo good!


Following up on my own topic. Kds, you said the 50mm doesn't vignette anymore. Does that imply that the shorter the focal length the more vignetting, and the longer the focal length the less vignetting with these lenses?

In other words, a Pentaxflex AK16 12.5mm lens (which exists) would vignette more than my 25mm lens?

Regards, C.


PostPosted: Tue Apr 23, 2024 9:24 am    Post subject: Reply with quote
connloyalist wrote:
kds315* wrote:
if you go for the 1.4/50mm then there is no vignetting anymore, but a bit more costly.
I have both and actually 2x of the 50mm, as it is sooo good!


Following up on my own topic. Kds, you said the 50mm doesn't vignette anymore. Does that imply that the shorter the focal length the more vignetting, and the longer the focal length the less vignetting with these lenses?

In other words, a Pentaxflex AK16 12.5mm lens (which exists) would vignette more than my 25mm lens?

Regards, C.


Yes indeed, shorter FL has vignetting as those lenses were not computed for larger sensors. I also have the 12.5mm but it vignettes way too much to use it...

My both 50mm lenses are very good, no complains! https://www.flickr.com/photos/kds315/albums/72157672400003047/





taken fully open from what I remember...
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