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Porst (Fujinon) 50mm f/1.2 question
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PostPosted: Fri Aug 11, 2017 7:10 pm    Post subject: Porst (Fujinon) 50mm f/1.2 question Reply with quote

Finally i got some time to dismantle the Porst Fujinon 1.2/50.

I had bought it from a seller who stated it was like new, but when it arrived the focus ring did not move one millimeter.... he would not take it back as he is not a professional seller but a private person, so this was my bad luck. In the end he refunded me 30 euros.....

This lens has a double helicoid, a very small and thin one and the larger one inside, both need to turn in order to make it functional. It took me quite some time to take it to pieces, clean the chewing-gum like grease off the threads and put it back together. I noticed oil had gotten between the lens elements the moment i took them out. The stains were not visible at first, but as soon as the elements were released from each other an oily layer made itself visible.

After putting it together again we had some days of rain and i did not bother to use it.

Today i made some test shots, but i feel something is not okay. Maybe one of the elements is upside down??

Thanks for looking and every bit of help is much appreciated!

Samples, jpeg from Sony A7:

1. Wide open f/1.2 a LOT of vignetting!!



2. f/5.6, look at the corners and edges, they're not sharp, i do not think this is normal



3. Even at f/8 you can still see the unsharpness in the corners:



PostPosted: Fri Aug 11, 2017 8:37 pm    Post subject: Reply with quote

I think the rear element could be relitivly easy to put in backwards compared to the rest that will seem more obvious, so you might want to double check that one.


PostPosted: Sun Aug 13, 2017 2:23 pm    Post subject: Re: Porst (Fujinon) 50mm f/1.2 question Reply with quote

I'd say something is wrong. Here is a sample of mine at f/5.6 I think. (Sony A7)



PostPosted: Sun Aug 13, 2017 2:33 pm    Post subject: Reply with quote

Looks like the lens has severe coma, which will most likely be a flipped element. It could also be incorrect element spacing, but the former is more likely.


PostPosted: Sun Aug 13, 2017 5:11 pm    Post subject: Reply with quote

Thanks! I'll check as soon as i have some time, don't want to do this in a hurry....

Other than the coma it's showing at this point: what a great piece of optics it is!

Cheers, René.


PostPosted: Tue Aug 15, 2017 3:05 pm    Post subject: Reply with quote

There's surely something wrong.
A glass misaligned ? I had this issue with a Cyclop.

But I like very much the pictures it delivers like that. I see a kind of nice 3D effect.