Strange marks on front element - coating degraded?

StewartR

StewartR

Messages
11,513
Name
Stewart
Edit My Images
Yes
Has anyone seen anything like this before? It's the front element of a Canon EF 24-70mm f/2.8 L II USM. It looks to us like the non-reflective coating is degrading somehow. This does not appear to be abrasion caused by over-enthusiastic cleaning. We see that a lot and this looks different.

What's particularly odd is that we've seen his sort of thing before - not very often, but a few times - and it's always the same type of lens, the Canon 24-70 Mk II.

It seems like we're not the only ones either - see post #17 here: http://www.canonrumors.com/forum/index.php?topic=19396.15

Any ideas what's going on here?

15512-1464776465-629f93d374e6e1457b8b1a13935b1382.jpg
 
Last edited:
Looks just like my glasses where the anti reflective coating is wearing off.
Had the same happen on some compact cameras where the LCD screen has lost its coating and also seen it very rarely on building glazing as part of my work.

Could be a coating issue where it hasn't adhered to the glass properly during manufacture. More likely I would have thought is its the result of poor cleaning which I would have thought your lenses are particularly susceptible to due to users not taking as much care as they should.
A scratch in the coating invisible to the naked eye could be enough to encourage the coating to start deteriorating.
 
Last edited:
I've just checked my service records and this is the FIFTH Canon 24-70mm Mk II lens which has had this problem. We haven't seen it on any other lens.
 
Without knowing the manufacture process and specs of this lens against others I can't see why it would be any different, but it's entirely possible it has a unique coating spec that just happens to be less robust.

Do the date codes suggest they are all from the same batch? Unlikely I would have thought as I guess you increased your stock over a period of time.
 
bass_junkie83 said:
Without knowing the manufacture process and specs of this lens against others I can't see why it would be any different, but it's entirely possible it has a unique coating spec that just happens to be less robust.
Click to expand...
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.
bass_junkie83 said:
Do the date codes suggest they are all from the same batch? Unlikely I would have thought as I guess you increased your stock over a period of time.
Click to expand...
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.
 
bass_junkie83 said:
Without knowing the manufacture process and specs of this lens against others I can't see why it would be any different, but it's entirely possible it has a unique coating spec that just happens to be less robust.
Click to expand...
It's not necessarily the coating itself that is different - if they use a different glass for the front element, then it might be harder to coat (or need more/different cleaning before coating). Small things like a different coefficient of thermal expansion for a different glass can also play a part.
 
twist said:
You should buy more nikon glass.... oh wait.
Click to expand...
Damn! Beat me to it.

Last complaint was how bad Nikon was. I wonder what it will be next... :)
 
My daughter has a canon with a 18-55stm kit lens. That appears to have a very soft front coating that flakes like that rather than just scratching. It looks to me like the coating is not really adhering to the lens so any scratch goes through it causes a problem.
 
Was it covered by warranty?
 
Ouch, drop that in the round file. It is caused by the coating delaminating from the glass, probably from inferior prep work on the glass prior to coating to remove all contaminants. On the bright side, at least it wasn't on a really good lens that this happened.
 
Last edited:
  • Like
Reactions: BBR
MatBin said:
Was it covered by warranty?
Click to expand...
The one which happened on 2013, which was within a year of the lens being purchased, was covered by warranty. The others all developed after the 12-month warranty period, so they weren't.

Having said that, I've only just identified the pattern and spotted that these particular lenses seem to have a unique vulnerability. I'm concerned that I might be facing another dozen repair bills in the near future, plus there's the risk to my operations. So at the same time as sending the latest one in to Elstree, I've asked Canon UK what they're going to do about the wider issue.
 
GT von said:
It is caused by the coating delaminating from the glass, probably from inferior prep work on the glass prior to coating to remove all contaminants.
Click to expand...
You sound pretty certain of that. But I don't think our paths have crossed before, so I do t know how to evaluate this information. Would you mind elaborating on why you're so certain? (I mean, I read somewhere that there are people who offer opinions on the internet and who do actually know what they're talking about. I'd like to think you're one of them.) And if that is the cause, how does the "inferior prep work" actually happen? Why might it happen to lenses manufactured years apart, and why might it affect only this type of lens?
GT von said:
On the bright side, at least it wasn't on a really good lens that this happened.
Click to expand...
See, childish comments like that don't help your credibility. That thing about people knowing what they're talking about...
 
brman said:
My daughter has a canon with a 18-55stm kit lens. That appears to have a very soft front coating that flakes like that rather than just scratching. It looks to me like the coating is not really adhering to the lens so any scratch goes through it causes a problem.
Click to expand...
That's interesting. Can you post a picture of the front element? It would be useful to compare...
 
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.
 
StewartR said:
You sound pretty certain of that. But I don't think our paths have crossed before, so I do t know how to evaluate this information. Would you mind elaborating on why you're so certain? (I mean, I read somewhere that there are people who offer opinions on the internet and who do actually know what they're talking about. I'd like to think you're one of them.) And if that is the cause, how does the "inferior prep work" actually happen? Why might it happen to lenses manufactured years apart, and why might it affect only this type of lens?
See, childish comments like that don't help your credibility. That thing about people knowing what they're talking about...
Click to expand...
But name calling makes you sound like you do know what you are talking about evidently.
Research it yourself, I'll say no more.
 
bass_junkie83 said:
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.
Click to expand...

The issue will be proving that it is an inherent problem with the lens rather than the way the lens has been treated, which I guess is why Stewart is trying to establish a pattern of the fault including outside of his business :)
 
Return it stating sales of goods act unfit for purpose!
 
gramps said:
The issue will be proving that it is an inherent problem with the lens rather than the way the lens has been treated, which I guess is why Stewart is trying to establish a pattern of the fault including outside of his business :)
Click to expand...

Yep, you are correct.
With Stuarts extensive range of lenses, multiple copies of each and seemingly exemplary record keeping, well if he can't do it no-one can.
 
What does he do for a living? What's he photographing?
 
bass_junkie83 said:
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.
Click to expand...

gramps said:
The issue will be proving that it is an inherent problem with the lens rather than the way the lens has been treated, which I guess is why Stewart is trying to establish a pattern of the fault including outside of his business :)
Click to expand...

Could you argue these faults when it's a business renting out lenses. Stewart may have little control of the care of the lens when out of his possession at rental.?... It's just something which springs to mind when I was on the tools and the warranties would be limited further, due to heavy use and not sure what Canons stance maybe on this or their terms and conditions.

Does seem annoying and a intermittent faulty manufacturing process by the look of thinks.
 
Back to being serious for me, it would seem like the only way to keep your quality up, Stewart, is to sell these lenses on before the problems start.

The affected lenses are no good to you but you need to have decent stock of these lenses.

If it was me, I'd start by selling on the October 2012, then the August 2013 and September 2013.
Hopefully you won't take too much of a hit cost wise, but it would be better than not having stock or stock you can't use.
The cost to you would have to be passed on to the customer, but broken down to a per rental amount over two years or so shouldn't be too much.

It seems unlikely that the problem will go away.
 
Last edited:
Mate of mine cleaned his 24-70 (Nikon) with some cheap microfibre wipes and "lens" cleaning solution to remove some oil, either the cloth or the solution or combo of both wiped away some of the coating, in short it looked much like that, yonks back when microfibre cloths first appeared on the market another friend of mine who worked with microscopes at the time advised me not to use them on coated glass, he said the coating is easily removed or damaged, as said here depending on the type of glass the coating/element can often be very soft. He was saying some of the internal lens elements on his scopes it was so soft just about any cloth could damage it, I never use microfibres on the front or rear elements for that reason and always use a protective filter, however I do feel sometimes the filters defeats the object of such fine glass and compromises clarity, flare and so on. What's the cost of replacing the front elements?
 
Swanseajack said:
Could you argue these faults when it's a business renting out lenses. Stewart may have little control of the care of the lens when out of his possession at rental.?... It's just something which springs to mind when I was on the tools and the warranties would be limited further, due to heavy use and not sure what Canons stance maybe on this or their terms and conditions.

Does seem annoying and a intermittent faulty manufacturing process by the look of thinks.
Click to expand...

If it was happening across the whole range of lenses you could argue that it is down to poor care of the lenses. But as it is limited to one specific model, I don't think Canon could counter by arguing that only 24-70mkii users are ham fisted monkeys while the users of every other lens are especially careful.

If it was down to poor care you would expect to see similar issues on other lenses.
 
GT von said:
But name calling makes you sound like you do know what you are talking about evidently.
Research it yourself, I'll say no more.
Click to expand...
Sorry, didn't mean to offend. I thought I said I was willing to believe that do know your stuff. Maybe I should have used a smiley.

But seriously, the reason I asked is that I know I don't know about this stuff. I can't research it myself because I wouldn't be able to evaluate whether what I was reading was correct.

So I'd be grateful if you're able to explain why you think this is what's happening.
 
bass_junkie83 said:
If it was down to poor care you would expect to see similar issues on other lenses.
Click to expand...
My point exactly. Same as with the Nikon zooms which I wrote about a couple of weeks ago - if the high failure rate was due to mishandling, then you'd expect to see it on more types of lenses.
 
kendo1 said:
Back to being serious for me, it would seem like the only way to keep your quality up, Stewart, is to sell these lenses on before the problems start.

The affected lenses are no good to you but you need to have decent stock of these lenses.

If it was me, I'd start by selling on the October 2012, then the August 2013 and September 2013.....
Click to expand...
Yeah, I think you're probably right. Though I want to hear back from Canon first. For all I know this was a known issue which they identified and quietly fixed back in 2014.
kendo1 said:
It seems unlikely that the problem will go away.
Click to expand...
Maybe. But I'm hopeful.
 
StewartR said:
Sorry, didn't mean to offend. I thought I said I was willing to believe that do know your stuff. Maybe I should have used a smiley.

But seriously, the reason I asked is that I know I don't know about this stuff. I can't research it myself because I wouldn't be able to evaluate whether what I was reading was correct.

So I'd be grateful if you're able to explain why you think this is what's happening.
Click to expand...


He won't be able to answer, even if he wanted to. He was hit by Mark's banhammer earlier today.

I've seen similar coating degradation but only on old (even back in the '70s they were old!) lenses. Didn't seem to have much affect on image quality but then again, I didn't do any back to back comparisons with unmarked copies.
 
I have a tiny spot of this right in the center of my Tamron 17-50 f2.8 and was wondering what it was...
 
StewartR said:
Yeah, I think you're probably right. Though I want to hear back from Canon first. For all I know this was a known issue which they identified and quietly fixed back in 2014.

Maybe. But I'm hopeful.
Click to expand...

That would be my guess.
 
StewartR said:
That's interesting. Can you post a picture of the front element? It would be useful to compare...
Click to expand...
Not sure I will be able to to be honest. With my daughters lens it (so far) is on the one scratch and it is very small, maybe 5mm long at most. But it does look the the edges are flaking rather than being a clean scratch (if you see what I mean). Hence my comparison with you lens.

I'll have another look at it later and see if it is possible to take a picture.

btw. this lens is less than 6 months old.
 
A few years ago I had a Citroen C5 which had a similar issue with the interior of the glass deteriorating giving a similar effect ,I know it's not a lens but it can obviously happen in glass manufacture and the makers can argue over a one off problem but if it's happening to several same model lenses then the fault lies with canon ,have you informed them yet and/or had a reply
 
My first thought was that it looks most like de-bonding of a doublet (but not quite right)... I have never seen AR coatings fail like that.
But, 7 pages of discussion on the topic as current as last march... all related to the 24-70/2.8 L II. In many cases it seems Canon claimed user error... at least initially.

http://www.canonrumors.com/forum/index.php?topic=19396.0
 
IIRC @gary43 knows about lens coatings, maybe he will be able to shed some light on the matter for you.
 
bass_junkie83 said:
Looks just like my glasses where the anti reflective coating is wearing off.
Click to expand...

Yes, I'd agree with this - my wife's glasses lenses coating was degrading and looked just the same...

Hope you manage to get it sorted with Canon...
 
Last edited:
Adam Priseman said:
I have a tiny spot of this right in the center of my Tamron 17-50 f2.8 and was wondering what it was...
Click to expand...

The Helios 44-5 on my Zenit has a very tiny area like this, but it doesn't seem to affect the optical quality in any noticeable way.

I put it down to normal wear and tear on a 30 year old lens.
 
I had this years ago on a much older lens and it turned out to be simply that the lens needed to be cleaned.

Once done the marks simply disappeared - it appears that even a small amount of a contaminant on the lens can alter the refractive index of the coating and cause these marks.

I expect you have already tried to clean them but just in case you haven't.....
.
 
maybe the affected lenses had a common customer who is using something bad to clean them?
 
You must log in or register to reply here.
Back
Top