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Stay away from petri lenses!
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PostPosted: Tue Mar 18, 2014 7:12 pm    Post subject: Stay away from petri lenses! Reply with quote
I know that there's a topic for "uncleanable" lens, but I decided to post a separate one for Petri (bayonet mount) lenses. They often appear for attractive price, and based on their register distance, they, besides mirrorless cameras, also can be adapted to Canon or Sony DSLRs. However, since these lenses are old, they often have fungus, dust or other problems, that you might think that can be easilly fixed. I bet you not.

Almost all treads and external screws are fixed with some kind of very stubborn glue. It is so strong, I was not able to soften it by submerging into acetone for 24 hours! Also, it holds things so strong, that I've broken two screwdrivers (non cheap, WIHA ones) while trying to unscrew such glued lens. The only way of softening that glue was to subject it to fumes of boiling NSF Primer for PVC pipes (NEVER try this, 99.99% chances of fire and 99% of lethal outcome, unless you have very well equipped chemical lab). Logical conclusion of using such strong solved was the fact, that not only glue, but all labels ant painted surfaces were gone.

Certain parts/lens assemblies are finished by pressing, so it is not possible to separate them without damage, and be sure, fungus grows exactly inside them.

This experience is based on about 10 Petri lenses, both fixed and zoom. Only one, easily to clean and adapt petri lens was Petri 2X teleconverter, because it appears to be made by same plant, which was manufacturing Vivitar 2X-1 teleconverter.


PostPosted: Tue Mar 18, 2014 7:52 pm    Post subject: Re: Stay away from petri lenses! Reply with quote
CuriousOne wrote:
I know that there's a topic for "uncleanable" lens, but I decided to post a separate one for Petri (bayonet mount) lenses. They often appear for attractive price, and based on their register distance, they, besides mirrorless cameras, also can be adapted to Canon or Sony DSLRs. However, since these lenses are old, they often have fungus, dust or other problems, that you might think that can be easilly fixed. I bet you not.

Almost all treads and external screws are fixed with some kind of very stubborn glue. It is so strong, I was not able to soften it by submerging into acetone for 24 hours! Also, it holds things so strong, that I've broken two screwdrivers (non cheap, WIHA ones) while trying to unscrew such glued lens. The only way of softening that glue was to subject it to fumes of boiling NSF Primer for PVC pipes (NEVER try this, 99.99% chances of fire and 99% of lethal outcome, unless you have very well equipped chemical lab). Logical conclusion of using such strong solved was the fact, that not only glue, but all labels ant painted surfaces were gone.

Certain parts/lens assemblies are finished by pressing, so it is not possible to separate them without damage, and be sure, fungus grows exactly inside them.

This experience is based on about 10 Petri lenses, both fixed and zoom. Only one, easily to clean and adapt petri lens was Petri 2X teleconverter, because it appears to be made by same plant, which was manufacturing Vivitar 2X-1 teleconverter.


Thank you for an interesting and valuable post. But could you clarify, please, the point about "bayonet mount".

Petri lenses were made in two different mount styles, in addition to the m42 screw mount Petris. There is the Petri proprietary breech lock mount, and (later) the PK mount, which is pure bayonet. I assume the lenses which gave you trouble had the Petri breech-lock mount. Most Petri lenses have that mount. But just wanted to be sure so I'm asking.

Now in general:

In my view the greatest impediment to lens repair enjoyment and bliss is that so many lenses are glued together. And I, too, have tried to open lenses when even acetone would not soften the horrid, thread-locking, glue. It's enough to drive you crazy. It's enough to reduce grown men to tears. It sucks!!

(And I'm sorry you broke your tools. That really sucks!)


PostPosted: Tue Mar 18, 2014 11:08 pm    Post subject: Reply with quote
I like those little gas soldering irons, get them hot and put the tip on the screw, hold it there for maybe a minute. I haven't had a screw beat me yet.


PostPosted: Wed Mar 19, 2014 12:57 am    Post subject: Reply with quote
Lloydy wrote:
I like those little gas soldering irons, get them hot and put the tip on the screw, hold it there for maybe a minute. I haven't had a screw beat me yet.


Well you make a good point and perhaps I did not read sufficiently closely and carefully. I agree with your take that screws most often can be freed, one way or another, even though thread lock was used. What give me fits is locked lens retainers and other situations where the thread lock is dispersed widely around and across a larger thread. Also, as the OP highlighted, acetone is not always able to "melt" the locking compound. The entire thing can quickly become a nightmare, depending on the brand of lens and the manufacturing approach used.


PostPosted: Wed Mar 19, 2014 4:43 am    Post subject: Reply with quote
Yes, by "bayonet" I meant petri breech lock lens.

So far, models taken down are:

80-200/4.5 (both big - with silver ring and "normal" ones)
200/4
55/2
35/2.8
2x teleconverter


PostPosted: Wed Mar 19, 2014 8:30 am    Post subject: Reply with quote
I don't think they glued them, maybe mainly because of time, some corrosion appeared. I heard from my friend that using a kind of anti-corrosion solution for several hours, we would be able to take out these screws.
I totally understand your frustration because I broke a screw driver and injured my hand once while I tried to unscrew the rear part of the SMC Pentax-M 50/1.7. I have two and both have the same problem.
Thank you for your information, now I have more reason to stay away from this brand.


PostPosted: Wed Mar 19, 2014 8:47 am    Post subject: Reply with quote
No, they are glued. I'll took camera to workshop shortly and will take some photos.


PostPosted: Wed Mar 19, 2014 11:00 am    Post subject: Reply with quote
[quote=" What give me fits is locked lens retainers and other situations where the thread lock is dispersed widely around and across a larger thread. [/quote]

That's murder to deal with, I took the elements out of a Tamron O1F X2 converter recently and the whole optic block is positioned by a fine thread and locking nut - which is all glued in place. It's guaranteed that once you've freed the damn thing it will never go back into the same place. Evil or Very Mad Luckily, it was fungused and I was converting it to a tube, but dismantling it effectively wrecked any chance of it working again.


PostPosted: Wed Mar 19, 2014 12:05 pm    Post subject: Reply with quote
Langstrum wrote:
I don't think they glued them, maybe mainly because of time, some corrosion appeared. I heard from my friend that using a kind of anti-corrosion solution for several hours, we would be able to take out these screws.
I totally understand your frustration because I broke a screw driver and injured my hand once while I tried to unscrew the rear part of the SMC Pentax-M 50/1.7. I have two and both have the same problem.
Thank you for your information, now I have more reason to stay away from this brand.


While not in disagreement with the OP, I take your point that corrosion oftentimes can be an issue where lens dismantling is concerned. The specific form I run into all too often, with both large and small items, is galvanic action over (perhaps) thirty or forty years. Galvanic action is, as the saying goes, "a bear and a spare". Sad


PostPosted: Wed Mar 19, 2014 12:21 pm    Post subject: Reply with quote
personally, i see very little reason to buy lenses with fungus because often they cannot be cleaned to the point where they are perfectly restored. especially these type lenses that are cheap when in pristine condition.

while interesting, the post shouldnt be to avoid petri lenses. ive had many and for the price, they performed very well. in fact the kuribayashi line are imo very good indeed and a great value. the 135/3.5 is one of my favorites and the most compact 135 ive ever used or seen. imo the post heading is misleading and provides somewhat of a misapprehension. the fact (?) that one cannot remove fungus from a lens is no reason to warn everyone off those lenses in general. far from avoiding petri lenses, perhaps avoid buying lenses with known faults, faults which are no fault of petri.


PostPosted: Wed Mar 19, 2014 1:54 pm    Post subject: Reply with quote
Same lens had other, non-glued screws too, and no "galvanic action" occured in past 30-40 years in them for surprise.

Why should you buy lens with fungus? because it is bargain and cheap, and many people have spare time that they can spend on lens cleaning, rather than making some $$$ Smile

Regarding the image quality of petri lenses, I've compared above mentioned models with the Helioses, Rokkors and some low-end stuff such as Lumetar. Definetly nothing to write home about. I've found a limited use of 35/2.8 coupled with Petri 2x teleconverter for some special effect shots - it creates very interesting haze effect, hard to reproduce with special f/x filters or in software.


PostPosted: Wed Mar 19, 2014 7:30 pm    Post subject: Reply with quote
rbelyell wrote:
personally, i see very little reason to buy lenses with fungus because often they cannot be cleaned to the point where they are perfectly restored. especially these type lenses that are cheap when in pristine condition.


If the price is right (or even free), however, I'd definitely encourage people to pick them up for practice!

I came across a Nikkor 135/2.8 that looked like a goner, it was caked with dust and fungus. To my surprise, it cleaned up perfectly, and I had a chance to get some valuable hands-on experience with spanner wrenches.


PostPosted: Wed Mar 19, 2014 10:14 pm    Post subject: Reply with quote
rbelyell wrote:
personally, i see very little reason to buy lenses with fungus because often they cannot be cleaned to the point where they are perfectly restored. especially these type lenses that are cheap when in pristine condition.

while interesting, the post shouldnt be to avoid petri lenses. ive had many and for the price, they performed very well. in fact the kuribayashi line are imo very good indeed and a great value. the 135/3.5 is one of my favorites and the most compact 135 ive ever used or seen. imo the post heading is misleading and provides somewhat of a misapprehension. the fact (?) that one cannot remove fungus from a lens is no reason to warn everyone off those lenses in general. far from avoiding petri lenses, perhaps avoid buying lenses with known faults, faults which are no fault of petri.


I must have bought 30 lenses with fungus, never had one that couldn't be cleaned. I've had some amazing bargains and only collectors care about perfectly restored condition, shooters know that a lens has to be damaged pretty badly before the IQ is noticeably affected.


PostPosted: Sun Mar 23, 2014 3:07 pm    Post subject: Reply with quote
You will not say this if you have try the Orikkor 50mm F2.


PostPosted: Mon Mar 24, 2014 12:47 am    Post subject: Reply with quote
rbelyell wrote:
personally, i see very little reason to buy lenses with fungus because often they cannot be cleaned to the point where they are perfectly restored. especially these type lenses that are cheap when in pristine condition.

while interesting, the post shouldnt be to avoid petri lenses. ive had many and for the price, they performed very well. in fact the kuribayashi line are imo very good indeed and a great value. the 135/3.5 is one of my favorites and the most compact 135 ive ever used or seen. imo the post heading is misleading and provides somewhat of a misapprehension. the fact (?) that one cannot remove fungus from a lens is no reason to warn everyone off those lenses in general. far from avoiding petri lenses, perhaps avoid buying lenses with known faults, faults which are no fault of petri.


Hear hear!


PostPosted: Wed Apr 02, 2014 6:45 am    Post subject: Reply with quote
iangreenhalgh1 wrote:
I must have bought 30 lenses with fungus, never had one that couldn't be cleaned.


Fungus really does a number on Rokkor 58/1.4 coatings.
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