Strange marks on front element - coating degraded?

That's my thinking too. Why they would use a unique coating for just this type of lens isn't clear to me, but it does seem to be the most logical answer.

Good question.

I have 18 of these lenses.
3 with date code 93 => August 2012 ... 1 with this problem (April 2013)
1 with date code 95 => October 2012
1 with date code 96 => November 2012 ... 1 with this problem (December 2015)
2 with date code 01 => January 2013 ... 1 with this problem (May 2016)
3 with date code 04 => April 2013 ... 2 with this problem (June 2015, March 2016)
2 with date code 08 => August 2013
1 with date code 09 => September 2013
3 with date code 14 => February 2014
1 with date code 30 => June 2015
1 with date code 38 => February 2016

So it could be an issue with early examples of this lens which has subsequently been addressed, in which case our newer ones won't suffer from it.
Or it could be that it typically takes a few years for the coating to degrade, in which case our newer ones might suffer from it at some point.

Trouble is, we'll never get any kind of official acknowledgement from Canon that there is an issue.

Just checked my copy of the lens, date code UW0212, and it doesn't seem to exhibit any defect of the sort... Hope this helps in your investigation :)

[EDIT] Ooops, my lens is the MK I 24-70 f/2.8 - sorry!!
 
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Just got back off my holls so a bit late to the party.
With 37 years in ophthalmic optics I've seen plenty of lenses like that. It's definitely faulty coating. If it's always the same element on the same model then more than likely a dodgy batch went through the coating process.
In the ophthalmic industry most commonly seen in "In house" budget coating systems, very rare from the premium brands.
 
With 37 years in ophthalmic optics I've seen plenty of lenses like that. It's definitely faulty coating. If it's always the same element on the same model then more than likely a dodgy batch went through the coating process.
Thanks. So if it's just a dodgy batch, the problem should be self-correcting?

The 5 lenses I've had with this problem were all manufactured between August 2012 and April 2013. I know nothing about Canon's internal processes, so I can't say whether one faulty batch of front elements might actually get put into lenses over a period of 8 months, but it's not totally implausible.
 
maybe the affected lenses had a common customer who is using something bad to clean them?
Seems unlikely that just one customer out of over 20,000 is able to damage lenses like this. But I checked anyway.

It turns out that we don't have a single customer who has hired all 5 of these lenses. I was able to identify 3 customers who have each hired 4 of them, and quite a lot of customers who have hired 3 of them. I took a close look at the 3 customers who had hired 4 of the lenses, but in each case (a) the dates didn't match, not even nearly - for example I can't see how a customer mistreating a lens in 2013 could cause its coating to fail in 2015 - and (b) they've hired other examples of the lens which haven't developed the fault..

So an interesting idea, but sadly not the answer.
 
Thanks. So if it's just a dodgy batch, the problem should be self-correcting?

The 5 lenses I've had with this problem were all manufactured between August 2012 and April 2013. I know nothing about Canon's internal processes, so I can't say whether one faulty batch of front elements might actually get put into lenses over a period of 8 months, but it's not totally implausible.
Generally speaking (ie not necessarily Canon) the issue of de-laminating coatings becomes apparent some time down the line maybe two to five years post manufacture. I would have thought that the first time one of the faulty lenses was returned to the manufacturer they would have known that it wouldn't be the last.
You would like to think that the issue would be self correcting, in that the coating departments quality control protocols would have spotted and rectified a non-compliance. As I mentioned, the first of the batch to fail in the field could be several years after production, and we can only guess how many lenses could potentially be affected in that time.
Either way I would suggest the problem is Canon's to resolve and "Sorry, it's out of guarantee." would not be an acceptable answer.
 
As regards customer abuse or miss-treatment. It would be very difficult to re-create this effect without causing some other identifiable issue ie damage to the glass under the coating, but even then scratching through the coating and into the glass shouldn't result in de-lamination.
 
Two thoughts struck me.

Getting Canon to accept there is an issue with the QC in the plant making and coating those specific front elements will by very hard. I wonder if this USA company "lensrentals" have experienced the same type of degradation?

In regard to user causation, what is the coating made of? The reason I ask is that DEET is a known problem that if I recall can degrade camera body plastics.......so is there perhaps a common factor such as all lens (in the case of DEET) were used in a mosquito area???
If there was a trigger event it was perhaps a single 'event' and the damage to the coating was progressive thereafter?

Stewart, best of luck getting a resolution in your favour with Canon.
 
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I thought people might like an update on this.

When I created the thread, 3 months ago, my inventory of these lenses was as follows:
3 with date code 93 => August 2012 ... 1 with this problem (April 2013)
1 with date code 95 => October 2012
1 with date code 96 => November 2012 ... 1 with this problem (December 2015)
2 with date code 01 => January 2013 ... 1 with this problem (May 2016)
3 with date code 04 => April 2013 ... 2 with this problem (June 2015, March 2016)
2 with date code 08 => August 2013
1 with date code 09 => September 2013
3 with date code 14 => February 2014
1 with date code 30 => June 2015
1 with date code 38 => February 2016

I presented the evidence to Canon UK. They did not admit to any knowledge of an inherent problem with this type of lens, but they did agree that if I suffered any further front element failures they would replace them free of charge.

And since then I have indeed continued to experience failures. The current situation is:
3 with date code 93 => August 2012 ... 3 with this problem (April 2013, July 2016, September 2016)
1 with date code 95 => October 2012 ... 1 with this problem (August 2016)
1 with date code 96 => November 2012 ... 1 with this problem (December 2015)
2 with date code 01 => January 2013 ... 2 with this problem (May 2016, July 2016)
3 with date code 04 => April 2013 ... 2 with this problem (June 2015, March 2016)
2 with date code 08 => August 2013... 1 with this problem (July 2016)
1 with date code 09 => September 2013
3 with date code 14 => February 2014 ... 3 with this problem (July 2016, July 2016, September 2016)
1 with date code 30 => June 2015
1 with date code 38 => February 2016
1 with date code 41 => May 2016

So that's now 13 front elements replaced out of 16 lenses that are more than 2 years old. And we're still not seeing anything like this on any other type of lens.
 
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Thanks for the update Stewart. That's a pretty shocking track record - clearly a problem with Canon's quality control. Did you drop an email to any other lens-rental companies to see if they see the same thing? You're probably in one of the few lines of business who could make meaningful stats on this!
 
Thanks for the update Stewart. That's a pretty shocking track record - clearly a problem with Canon's quality control. Did you drop an email to any other lens-rental companies to see if they see the same thing? You're probably in one of the few lines of business who could make meaningful stats on this!

I was going to suggest the same, lensrentals.com are quite active with blogging and stats about their inventory etc, so I would imagine they would be interested.
 
My old Nikkor 18-70 went that way after I unintentionally stored it damp.

I never really noticed it affecteing IQ much though.
 
It may be out of warranty, but can you argue it under statutory rights? I'll have to look it up to be sure, but I am pretty sure that there is something under your statutory rights that states that an item should be expected to last a suitable period of time which can be longer than a manufactures warranty.

Not sure what the cost of these lenses are new, but I'm pretty confident you can build an argument that it should be expected to last longer than 12 months without having to be repaired or replaced.

x2 ;)
 
Worrying to see that it's happening with 2016 lenses in a short time frame. I was going to buy one of these but I think perhaps I will leave it for a little while. Given the price of this lens that sort of defect is simply not good enough.
 
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My 24-70/2.8 MkII is still mint after three+ years :)

And I'd add, an awesome lens it is too!
 
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