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Praktica Pentacon 1.8 50mm modified to fit EOS
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PostPosted: Tue Apr 12, 2011 6:55 am    Post subject: Praktica Pentacon 1.8 50mm modified to fit EOS Reply with quote
Hi folks

I own a lovely Praktica Pentacon 1.8 50mm in PB mount but sadly it wouldn't hit infinity on my EOS 10d with an adapet. Also, the aperture mechanism seemed to sometimes stick wide open.

So I took it apart, fixed the aperture and machined the adapter down so it would fit in place where the PB mount had been. Sadly my repair on the aperture was a failure and it's now stuck wide open forever with epoxy.

Takes a nice pic though, I like the sharpness and contrast for wide open, these were taken late afternoon with the sun low in the sky. Seems sharper than my Helios 44-2 wide open.











PostPosted: Tue Apr 12, 2011 6:58 am    Post subject: Reply with quote
Sadly, infinity as marked on the barrel is still not in focus, I think the lens maybe now be sitting slightly too close to the sensor and is focusing past infinity.




This is why I think it may be focusing past infinity, it's not quick in focus but is closer, I had focused a fair bit closer than infinity so perhaps I can work out where infinity now is for this lens and mark it on the barrel?



PostPosted: Tue Apr 12, 2011 6:55 pm    Post subject: Reply with quote
No comments at all?


PostPosted: Tue Apr 12, 2011 9:32 pm    Post subject: Reply with quote
I tried to get a PB mount lens to fit my Pentax, getting the register distance right was a nightmare, and one I haven't gone back to yet. Rolling Eyes
My problem is, I turned the body down in the lathe to what I thought was right - it wasn't - and I've lost the bit of paper with my calculations and measurements on it, so I have no idea what I've done! Laughing

Perhaps it's easier to just buy the right lens ? Wink


PostPosted: Tue Apr 12, 2011 9:40 pm    Post subject: Reply with quote
Lloydy wrote:
I tried to get a PB mount lens to fit my Pentax, getting the register distance right was a nightmare, and one I haven't gone back to yet. Rolling Eyes
My problem is, I turned the body down in the lathe to what I thought was right - it wasn't - and I've lost the bit of paper with my calculations and measurements on it, so I have no idea what I've done! Laughing

Perhaps it's easier to just buy the right lens ? Wink


Aye, I've bought a M42 version of this lens because I think it has very nice IQ when working right. I only paid 4 quid for the PB version and the same now for an M42 version so it was worth trying a conversion as I spent 9 quid on the PB-EOS adapter with AF confirm chip!

The focus is a bit off in most of the test shots but you can see it is quite sharp where it is in focus, the contrast is good for wide open too.

I think where I went wrong with this modification is in trimming down the thickness of the adapter I ground down in diamter to fit where the PB mount was. The EOS register is 44mm and I think the PB one is 45.2. I could sort this problem out byt removing the adapter and putting in some shims but the aperture would still be stuck wide open. The aperture itself is fine, it's a problem with the rod that connects the aperture mechanism to the aperture ring and only a very minor problem, it was working when I put it back together but after turnign it a couple of times it stuck again.


PostPosted: Tue Apr 12, 2011 9:59 pm    Post subject: Reply with quote
It looks soft wide open to me I'm afraid. But most shots are mis-focused so it's a bit tricky to tell...grab a cheap tripod and take a few shots while slowly focusing and keep the sharpest shot as a test. My 50/1.8 PB mount is terrible wide open BTW Laughing


PostPosted: Tue Apr 12, 2011 10:50 pm    Post subject: Reply with quote
It is a lovely lens to use, I use mine a lot.

And even if you do FUBAR your lens mount, you can always use a reversing ring, it wouldn't be wasted.


PostPosted: Wed Apr 13, 2011 12:29 am    Post subject: Reply with quote
The same lens you can buy a working one for peanuts in M42 - may be on a Praktica body. So why bother?


PostPosted: Wed Apr 13, 2011 12:35 am    Post subject: Reply with quote
ManualFocus-G wrote:
It looks soft wide open to me I'm afraid. But most shots are mis-focused so it's a bit tricky to tell...grab a cheap tripod and take a few shots while slowly focusing and keep the sharpest shot as a test. My 50/1.8 PB mount is terrible wide open BTW Laughing


When my M42 copy gets here i'll do a 50mm shootout test like that, I have these to test against each other:

Pentacon 1.8/50 modified/knackered
Pentacon 1.8/50 M42
Helios 44-2 2/58
Helios 44-4 2/58
Industar-50 2.5/50
Meyer Domiplan 2.8/50

I also have a Pentax-M 2/50 and a Petri CC 1.8/55 but no adapters for them to fit my cam.

I might not bother testing the Domiplan, well all now how good it is...

I suppose it boils down to the Pentacon vs the Helios, we knwo the Helios has good bokeh and is quite sharp, I like the Pentacon to use, like Lloydy and I suspect it has better coatings than the Helios. The Industar is slower and I like it cos it's a pancake and easy to carry around. it's pretty sharp though, I think a little sharper than the Helos but we shall see...

I'm hoping to modify the Petri to fit my EOS because I'm told it's a wonderful lens...


PostPosted: Wed Apr 13, 2011 2:27 am    Post subject: Reply with quote
I had pentacon 50/1.8 PB mount. the plan was to converted to EOS. But I had no time to do it. I sold it for charity. That time I had other 50/1,8 ; CZ pancolar, pentacon M42, Nikon AI. The PB version is slight better to me than M42. I guess MC mean something.
Here's my shot in 1000D Canon handheld without adapter. No editing.




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