Lens mount “brassing” on 300mm f/2.8L II

R1-7D

EOS Rebel SL2
Jun 25, 2012
645
6
Canada
#1
I noticed yesterday that the lens mount on my Canon 300mm f/2.8L IS II is showing some wear. Specifically, the chrome coating has worn down to the brass underlay.

I also noticed some tiny brass filings around the pin hole where the camera body locks into the lens. I’ve since cleaned the filings out with a dampened Q-tip.

My questions to everyone are:

1) Would this issue of “brassing” warrant sending the lens in for repair? And, if so...

2) Does anyone have an estimate of cost for a lens mount replacement?

Thanks.
 

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Mt Spokane Photography

Spends too much time on this forum
Mar 25, 2011
14,749
231
#2
I'd ask Canon. The tolerances between the camera body lens mount and the lens are very precise, if either is bent a slight amount, you can see the issue. Its likely the camera side, the lens side, or maybe both.

Cost for a new mount is pricey, so ask Canon to fix it and see if they will do it Gratis!.
 

R1-7D

EOS Rebel SL2
Jun 25, 2012
645
6
Canada
#3
I'd ask Canon. The tolerances between the camera body lens mount and the lens are very precise, if either is bent a slight amount, you can see the issue. Its likely the camera side, the lens side, or maybe both.

Cost for a new mount is pricey, so ask Canon to fix it and see if they will do it Gratis!.

Thanks for the response.

I have checked all my other lenses and none exhibit this wear. I bought the 300mm used, so it’s likely that the seller’s camera caused the marking.

Pricey? Great... :(
 

privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
7,147
142
118
#4
1) Not until it is time to sell it as it will probably happen again.

2) That kind of thing comes under the 'fixed price servicing' and isn't generally too bad, I'd estimate $150 going from my past experiences.
 

privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
7,147
142
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#5
Obviously if you bought it like that (your other lenses don't have the mark) then getting it fixed now would be a good idea. Don't worry about tolerances or de-centering as it is clearly just a sticky body lens release pin and that one small area won't impact the mating surface enough to impact alignment.
 

R1-7D

EOS Rebel SL2
Jun 25, 2012
645
6
Canada
#6
1) Not until it is time to sell it as it will probably happen again.

2) That kind of thing comes under the 'fixed price servicing' and isn't generally too bad, I'd estimate $150 going from my past experiences.
Thank you for the reply.

Perhaps I’ll leave it then. I was just worried about seeing the little metal filings, and I know brass is a relatively soft metal, so it makes sense that the camera locking pin is shaving the brass a bit.

$150 isn’t too bad, especially with the CPS discount applied.
 

R1-7D

EOS Rebel SL2
Jun 25, 2012
645
6
Canada
#7
Obviously if you bought it like that (your other lenses don't have the mark) then getting it fixed now would be a good idea. Don't worry about tolerances or de-centering as it is clearly just a sticky body lens release pin and that one small area won't impact the mating surface enough to impact alignment.

Thanks again.

I might leave it for now then and see if my 1DX2 causes further shavings. If it does, then I’ll go ahead and ship it to Canon.

If the problem doesn’t persist, then I’ll just leave it if it won’t affect image quality.
 

privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
7,147
142
118
#8
I had a 1VHS do it to a 70-200 f2.8 IS once, I left it for a long time, I eventually sent the lens in for something else and they replaced the mount under the umbrella of the other work.

Thank you for the reply.

Perhaps I’ll leave it then. I was just worried about seeing the little metal filings, and I know brass is a relatively soft metal, so it makes sense that the camera locking pin is shaving the brass a bit.

$150 isn’t too bad, especially with the CPS discount applied.
 

privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
7,147
142
118
#9
It absolutely won't affect image quality.

Thanks again.

I might leave it for now then and see if my 1DX2 causes further shavings. If it does, then I’ll go ahead and ship it to Canon.

If the problem doesn’t persist, then I’ll just leave it if it won’t affect image quality.
 
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AlanF

EOS 5DS R
Aug 16, 2012
4,137
335
#11
The 300mm f/2.8 II is the only one of my lenses to show brassing, and it diidn't affect the sale price.
 

YuengLinger

EOS 6D Mark II
Dec 20, 2012
2,023
65
Southeastern USA
#12
Years ago Moose Peterson said in one of his videos that a very common cause of stubborn sensor spots comes from tiny bits of metal flaking off the lens and body mounts. He recommended frequently wiping both with microfiber to reduce how much falls onto the sensor.
 

privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
7,147
142
118
#13
I don't agree with Mr Peterson. In normal use there is no effective wear on the mounting surfaces as the coatings are more then hard enough to deal with the minimal mechanical loads imparted on them, in this particular instance there was obviously an issue with the lens release pin on a body that has caused unusual wear that might cause dust spots, but this is an unusual case.
 

YuengLinger

EOS 6D Mark II
Dec 20, 2012
2,023
65
Southeastern USA
#14
I don't agree with Mr Peterson. In normal use there is no effective wear on the mounting surfaces as the coatings are more then hard enough to deal with the minimal mechanical loads imparted on them, in this particular instance there was obviously an issue with the lens release pin on a body that has caused unusual wear that might cause dust spots, but this is an unusual case.
What I notice, if I wipe my mounts every six months or so with a lens wipe, is a slight amount of grayish residue on the wipe. I assumed this was from a combination of oxidation and slight friction during lens swaps.
 

R1-7D

EOS Rebel SL2
Jun 25, 2012
645
6
Canada
#15
The 300mm f/2.8 II is the only one of my lenses to show brassing, and it diidn't affect the sale price.

Thank you for the response.

Did you ever consider having the mount replaced?

Also, did you notice any brass shavings start to accumulate over time?
 

R1-7D

EOS Rebel SL2
Jun 25, 2012
645
6
Canada
#16
I don't agree with Mr Peterson. In normal use there is no effective wear on the mounting surfaces as the coatings are more then hard enough to deal with the minimal mechanical loads imparted on them, in this particular instance there was obviously an issue with the lens release pin on a body that has caused unusual wear that might cause dust spots, but this is an unusual case.

Ultimately, I think I’ll send the lens in. For the time being I will keep an eye on it and follow the advice of keeping the mount clean either by wiping it or using a dampened Q-Tip. The last thing I want is for a metal filing to make its way onto my sensor.
 

Don Haines

posting cat pictures on the internet since 1986
Jun 4, 2012
7,324
314
Canada
#19
It should not need the whole mount replaced, this should just be a simple ring.... undo a few screws, pop off the ring, put a new one on, and calibrate.....

Of course, all of us forum users (myself included) are just guessing... send some pictures to Canon service and ask them.
 

R1-7D

EOS Rebel SL2
Jun 25, 2012
645
6
Canada
#20
It should not need the whole mount replaced, this should just be a simple ring.... undo a few screws, pop off the ring, put a new one on, and calibrate.....

Of course, all of us forum users (myself included) are just guessing... send some pictures to Canon service and ask them.

Thank you. I spoke with them on the phone this morning. The phone agent said that it's impossible to tell unless they can physically evaluate the lens. The best guesstimate he could offer me was around $450, mostly accounting for the technician's time. With that said, you could be right -- I am not sure if the whole mount needs replacing, as there's no wear anywhere else. It's just that ring that sits flush against the camera mount that is worn.