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01-10-2009, 03:40 PM   #31
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QuoteOriginally posted by wavecurrent Quote
Yes, I have taken a K 24/2.8 apart. And it's almost the same as the M35, the rear end is actually a little bit simpler in its design. The reason was that I suspected some fungus in the front lens grope, but I think it's even worse. There are two lenses cemented together, and they are coming apart
Look at the pictures, what do you think??!!
Hm, hard to decide. The reflection obscures the problem to a big degree. Nevertheless it does, on first glance, not really look like fungus. Separation might be true. You could repair that, but it is tedious... Nevertheless separation need not be the death spell for the lens. It might be, that it doesn not show in the photos or you will only have a slight loss of contrast. One thing that helps in thiese cases, is shielding the lens element from stray light, which means, using a good lens hood is really important.

Ben

01-13-2009, 10:05 AM   #32
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QuoteOriginally posted by ovim Quote
Haven't done it myself but heres a thread on mflenses.com on repairing cemented lenses.
Thanks for the link, interesting reading.

QuoteOriginally posted by Ben_Edict Quote
Hm, hard to decide. The reflection obscures the problem to a big degree. Nevertheless it does, on first glance, not really look like fungus. Separation might be true. You could repair that, but it is tedious... Nevertheless separation need not be the death spell for the lens. It might be, that it doesn not show in the photos or you will only have a slight loss of contrast. One thing that helps in thiese cases, is shielding the lens element from stray light, which means, using a good lens hood is really important.

Ben
Ben, Iím quite sure itís the cemented lenses causing this problem. No other lenses seems to be affected, and yes the contrast is really bad wide open. Iím fortunate to have an A24/2.8 as well, and when compared you have to stop-down the K-version to 5.6-8 for a decent result. I might try to repair it someday, or maybe I can get it fixed somewhere.

Mike
01-13-2009, 10:10 AM   #33
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QuoteOriginally posted by wavecurrent Quote
Ben, Iím quite sure itís the cemented lenses causing this problem. No other lenses seems to be affected, and yes the contrast is really bad wide open. Iím fortunate to have an A24/2.8 as well, and when compared you have to stop-down the K-version to 5.6-8 for a decent result. I might try to repair it someday, or maybe I can get it fixed somewhere.

Mike
Mike, if you can spare that lens, you should give it a try. Otherwise recementing is expensive and most repair shops won't do it anyyway. It is really only worth a commercial repair, if the lens is very valuable.

Ben
01-18-2009, 10:18 AM   #34
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Never confuse enthusiasm for talent or skill
I just magically transformed an SMC-A 50mm F1.4 into a SMC-M 50mm F.4
... .... .... ...
If anyone has a micron sized spring please let me know...

Plus the lens isn't that particularly clean (had fungus)... Stupid cloths.

Thats the of my adventures into lens repair... well in good lenses at least.

01-18-2009, 11:15 AM   #35
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QuoteOriginally posted by edumad Quote
If anyone has a micron sized spring please let me know...

Plus the lens isn't that particularly clean (had fungus)... Stupid cloths...
Just one junk camera will have enough spare parts for several mistakes. I think I've used up all the tiny brass springs I had (bearings too).

Fungus can etch the lens coatings in bad cases. If your lens has splotches where the coating looks different, it might be coating damage from fungus.
01-18-2009, 03:24 PM   #36
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After crawling on the floor with a torch light for quite some time... Hurray spring found!

phew...
04-27-2009, 10:49 PM   #37
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This is such great info for Pentax lens followers. Thanks for all your contributions.
04-28-2009, 05:06 PM   #38
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QuoteOriginally posted by frank Quote
That's really true

I opened up another lens last night, my second time doing lens surgery:


And the reason why I opened it up? The aperture stayed wide open all the time due to these oily aperture blades (the left two blades were after cleaning):


After about 1 hour, the lens was put together, beautiful as new again:
Are you a trained repairman or just gifted when it comes to doing that kinda stuff?

I AM IMPRESSED! WOW!

I have a MF lens that will not open the aperture blades with the aperture ring. The blades only open up with the auto aperture function.


So I have a Vivitar 100-300 f/5 that I can use wide open with the AE function on the camera or at f/22 with the green button.

Any suggestions?

04-28-2009, 06:32 PM   #39
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QuoteOriginally posted by res3567 Quote
Are you a trained repairman or just gifted when it comes to doing that kinda stuff?

I AM IMPRESSED! WOW!

I have a MF lens that will not open the aperture blades with the aperture ring. The blades only open up with the auto aperture function.


So I have a Vivitar 100-300 f/5 that I can use wide open with the AE function on the camera or at f/22 with the green button.

Any suggestions?
Nah, I'm not really a trained repairman, just have some guts to open up a cheapy lens like the Cosina I wouldn't have opened it if it's a Pentax M or A50/1.4 (for my first lens to practice). But since then I've opened more than 10 lenses already, including some Pentax lenses

Never really tried any zoom lens yet except a Vivitar 70-210 (to repair its A contact). Seems a lot harder than a simple prime lens. But since it's just the aperture blades problem, I think you should be able to fix it by yourself if you dare

Good luck.
05-26-2009, 02:08 AM   #40
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I have fungus similar thing present on an element bordering the aparture blades. This is 1.4/50mm SMC-M lens in K mount.

I was hoping to get to it from back but that isn't the case since i can only remove 2 elements. Do i have to open the front? And will i have to remove elements one by one from the front to come to aparture blades?
Thank you in advance!
05-26-2009, 06:11 AM   #41
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QuoteOriginally posted by Mushroom_Toy Quote
As long as its not an auto lens it should be ok to dissasemble it, but being that ita a bigger lens it will be harder to put back together.
i have an auto vivitar 24mm 2.8 lens with what looks like an exoskeleton floating between some of the elements. is it just harder to put back together because it has more parts to deal with? i think i might just go with the refund if its too difficult.
05-26-2009, 02:55 PM   #42
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hi there,

I've posted this in another thread but these are great for getting the front ring off of a lens



Its a rubber pipe cap. I got this from a store that sells rubber products but I imagine you should be able to get one from any big hardware store, and they come in various diameters so you should be able to get one to match your lens. And because its rubber there less of a chance of it damaging the front lens element. I've tried other methods without much luck, but with this I've even managed to get the front ring of a lens with damaged filter thread. There was a 50mm f1.2 on ebay and I think in the market place here recently that had been destroyed by someone drilling holes in the front ring and scratching the front element. Please don't do this to a lens ever!
05-27-2009, 03:14 AM   #43
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Pentax 1.4/50mm SMC-M lens separation

Hi!
I already wrote some of you privately regarding quickest way to the Pentax 1.4/50mm SMC-M inner elements. I had to go through front, putting even aparture mechanism off. Anyway i was so happy to reach faulty element but when it popped out i saw there are two of them glued and they suffer from separation.

Does anyone know how to fully separate them?

I read heating up to 150 degrees Celsius might help. But that was about older lenses. And i already tried heating some old ones and they cracked. But i did sucessfully separated 8/500mm front element and just put it together without glue / grease and the photos are superb.

Please help, this SMC is otherwise perfect.

Last edited by Pancolart; 05-27-2009 at 03:22 AM.
05-27-2009, 04:08 AM   #44
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QuoteOriginally posted by Pancolart Quote
Hi!
I already wrote some of you privately regarding quickest way to the Pentax 1.4/50mm SMC-M inner elements. I had to go through front, putting even aparture mechanism off. Anyway i was so happy to reach faulty element but when it popped out i saw there are two of them glued and they suffer from separation.

Does anyone know how to fully separate them?

I read heating up to 150 degrees Celsius might help. But that was about older lenses. And i already tried heating some old ones and they cracked. But i did sucessfully separated 8/500mm front element and just put it together without glue / grease and the photos are superb.

Please help, this SMC is otherwise perfect.
Heat is the best way to separate glued elements. Just take your timew! Put the elements in the COLD oven and then heat it slowly to the required temperature - and vice versa let the whole assembly cool down slowly in the oven after switching off. Then the lenses shouldn't crack.

Chemically you could try acteone for dissolving the glue, but it doesn't work with all glues and it might damage the coating. You could try it on an old non-valuable lens, first.

If you do not recement an originally cemented lens assembly it might work fine optically, but you will get increased ghosting and flare, as you would create two additional glass-air surfaces.

Ben
05-28-2009, 05:39 AM   #45
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Thank's Ben! I guess there is no other way then to try it. Can i put it in the water and slowly boil? I read somewhere one can use different oils instead of cement. Any experience?
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