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03-17-2016, 10:01 AM   #1
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slow aperture on M 50 1.4

Hey friends,

got an M 50 f/1.4 and I was stoked about the condition. at home I discovered in some testing situations that the aperture is kinda sticky and goes only "slow" from f22 to open. Is there anything I can do about that without dismantling or brining it to the repairshop? I talked to the guy and he told me about 200+ Euro for a lens repair...? Wft?
Will it come back to life if I use the blades a lot? open and close them manually? Hmmm I am a bit disappointed. looked so good that glas...

03-17-2016, 11:41 AM   #2
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QuoteOriginally posted by i5_david Quote
Hey friends,

got an M 50 f/1.4 and I was stoked about the condition. at home I discovered in some testing situations that the aperture is kinda sticky and goes only "slow" from f22 to open. Is there anything I can do about that without dismantling or brining it to the repairshop? I talked to the guy and he told me about 200+ Euro for a lens repair...? Wft?
Will it come back to life if I use the blades a lot? open and close them manually? Hmmm I am a bit disappointed. looked so good that glas...
If you are feeling adventurous, the disassembly database has an entry for your lens. I cleaned my M 28mm last weekend, it took me 2-3 hours, and I'm a beginner with lenses - but not with screwdrivers
03-17-2016, 11:51 AM - 1 Like   #3
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See this disassembly video:
03-17-2016, 12:13 PM   #4
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Thanks for your help already!!! It doesn't look that crazy hard to open up... but do I need to disassamble the complete unit? The attached video shows the blades at 2:26 already. Is this the moment I can actually clean the blades? Or do I need to get each of them out of the lens to clean them properly?
How do I clean them? alcohol?
I am a bit afraid that dust will get into the lens when I go on my adventure....

EDIT: Do you think the problem are the blades or can it also be the spring that brings the aperture wide open? Then I wouldn't be able to fix that, right?

03-17-2016, 01:24 PM   #5
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hey dcshooter, thank you for your detailed description. I am right now following this dude: https://www.youtube.com/watch?v=-rlDO5Qj6cU#t=71
since its a bit different with the 50 1.4. but I am ready to work on the blades. In fact I just opened it but I dont have the fluid here and stores are closed since some hours already.

just a couple things:
- you mean the normal fluid I would use to fire up a zippo lighter or any special fluid?
- what happens when the drop goes through the blades into the lens... does it go/fly away/disappear like pure ethanol?

Thanks for your outline I will take a shot tomorrow and try it
03-17-2016, 02:03 PM   #6
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Thanks mate, really appreciate your help here!
I will go downtown and get myself a bottle of lighter fluid and give it a ride. I will be sure to let you know here if it worked. That would be so cool, since I really looked forward to use this lens.
(in fact I got it on ebay (marketplace) in comination with a ME, the 50 1.4 and 200 f4 for 45€ - so happy about this deal, haha )
03-18-2016, 08:56 AM   #7
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QuoteOriginally posted by i5_david Quote

EDIT: Do you think the problem are the blades or can it also be the spring that brings the aperture wide open? Then I wouldn't be able to fix that, right?
It's unusual for the rest of the mechanism to have trouble. I have one lens like that, and it's a screw-mount lens so it doesn't need fast aperture blades. Resist the temptation to put a drop of oil somewhere just in case. .
03-18-2016, 01:26 PM   #8
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So, came back today and after the opening the lens test yesterday I did it. longer story short: I bought a bottle of lighter fluid for 2,20€ and now its working again! HAHA
THANK YOU so much dcshooter!!! Because of your awesome outline I managed to repair my lens. great feeling. love it
After I put it together I noticed a small little tiny hair... that actually bothers me, so I think I have to do it one more time.
(One thing, after I put it together the lens' focus sounded a bit like there is sand in the mechanism (NO WAY, No Chance that that happened). Its better now, but these noises were kinda strange. Turned the focus back and forth and back and forth and now its better but why is this?)

@soti: thanks for pointing this list out of videos how to open up lenses. Great resource!

03-23-2016, 07:56 PM   #9
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dcshooter is The Man :-)

i tore down a canon fd 50/1.4 a couple of days ago for oily blades... i stupidly took it down too far, basically disassembled the focus mechanism, and it took me half a day just to grasp how the internal focus ring could drive the top group assembly straight down: gregpotter.net - Canon New FD 50mm F/1.4 Disassembly from the Front

i got the blades out, blew 'em clean with carb cleaner, but they were still sticky, ended up with all eight blades disassembled in pieces on the bench :-0

the amount of screw torque on the blade assembly is apparently critical to proper operation.

got it all back working, infinity adjusted, then noticed some very tiny bubbles somewhere in one of the rear elements...

live and learn, glad to hear that someone had better luck with their lens teardown.
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