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Butchered Prakticar/Pancolar, help needed
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PostPosted: Sat Mar 25, 2017 8:04 pm    Post subject: Butchered Prakticar/Pancolar, help needed Reply with quote

Time ago i bought a Prakticar f/1,8 80mm in PB mount, roughly converted to PK mount.
Knowing that practically is a Pancolar (worse build but -probably - better coating), i bought it on Ebay.
The price was affordable because the previous buyer returned it because of stuck/not working diaphragm.
The lens waited my return for a couple of months, but when we opened it it was pretty evident that the lens had been butchered so badly that there is no way to repair the diaphragm without a "donor lens".
The part that has been badly ruined is the one that sits under the bayonet. Unscrewing the rear of the lens, the component i need is the one that sits immediately under the bayonet itself.
I have only two other PB lenses, one is a Sigma-made zoom, and the other is a 28mm (probably german made, but the bayonet looks different).

I know that some of the forum users are used to open their lenses, to clean the glasses or free the iris leaves.
The 80mm Prakticar is a very nice, desirable objective, so i guess a few of you own one.
What i'm asking for is quite simple. Is there any other (hopefully cheaper!) Praktica lens with the same kind of mount?
The two i have are completely different, the 28mm has no screws at the back and the other is a Sigma!
My only hope is to find a 50mm or 135mm with the same kind of mount, but i'm trying to get some informations first...

This is the back of the butchered lens:




cheers

Paolo


PostPosted: Sun Mar 26, 2017 9:21 pm    Post subject: Reply with quote

You can find "cheap" CZJ made Prakticar lens, for example the first version of 50mmF/1.4 , the first version of 50mmF/1.8, 20mmF/2.8.
Those CZJ made lens has identical mechanical mount base, the best one is 50mmF/1.8 (optically same as Pancolar 50mmF/1.Cool which
has the same F1.8 as Pancolar 80/1.8 which uses the same internal register which tells the PRAKTICA camera which F-stpp in in use now.

However it is the next to impossible to find a cheap first version of 50mmF/1.8 lens today. If you do not use PRAKTICA camera with
films, those internal registers do not affect your say mirrorless camera's exposure. In this case you can use any CZJ made lens mount
interchangeably I think.

Newer PENTACON made Prakticar lenses use a bit different mechanism, so you may have a problem for Prakticar 80mmF/1.8 lens. Also
you may have to change/eliminate its internal register (if you open the mount you can see it, normally attached to the mount base).

good luck .../koji


PostPosted: Mon Mar 27, 2017 12:00 am    Post subject: Reply with quote

Thanks for the reply, and thanks for the suggestions concerning CZJ made Prakticar lenses with a similar mount.
Though, from a couple of things you have written, i'm not sure you understood the problem.
The lens doesn't have to inform the camera about anything, i'm not using a Praktica (film camera). I'd be happy to use the lens in stop-down, if only i could operate the iris! The problem is due to the fact that the (badly made) conversion messed with the component that sits under the bayonet, so that the diaphragm ring can't move the diaphragm leaves anymore. The diaphragm in itself is fine, if i close and open with my fingers, accessing the lever from the back of the (opened) lens, everything is fine. The blades are all there, not oily, with no gum.
I don't know what you refer to when you write about "register". I've never used this word for anything but the distance between the flange of the lens and the sensor/film.
The "register" of the lens has been already adjusted. Doing so the previous owner modified the part that transfers the movement of the diaphragm ring to the lever that operates the diaphragm assembly. It is nearly destroyed, beyond repair, probably for lack of experience or because he couldn't have access to a decent mill/lathe.
If i can find the part i need, i will get rid of the original bayonet (which has been adapted with a Pentax M42 to PK ring stuck on top of it - and missing a section of the circumference!), and i will replace it with a non-infinity M42 to PK flange, milled and drilled to reuse the original screws. These flanges are available in 1mm and 0.5mm of thickness, thinner than the original bayonet (allowing to compensate for the register difference, if needed).

The lenses you propose as donors should be everything but cheap, but i found a cheaper lens that seems to have a similar mount, with the screws positioned the same way.
ALL the Prakticar's made by Sigma or derived from Meyer objectives have a different mount.
Sigma's have 3 screws, and Meyer's, like my 28mm f/2.8, have none:



The 135mm f/3.5, the PB version of the original CZJ Sonnar, has more or less the same mount:



If anybody has ever opened both lenses (80mm and 135mm), i'd be very interested in knowing if both have the same structure, under the bayonet

cheers

Paolo