I agree that the issues could be more involved when looking at just one lens. But just because it's the same process doesn't mean every piece of glass is treated by the same machine - not even even all front elements. And Canon is always updating their coatings on their best glass to improve them.
It also does not mean that a bad batch or more than one bad batch will not occur. That sort of thing happens with other highly controlled manufacturing - pharmaceuticals, automotive parts, Ben& Jerry's Ice Cream (fun tour - employees love it when a bad batch happens 🙂 etc. A bad batch or several batches would be the responsibility of the manufacturer. Coatings on lenses may seem a bit magical or mystical, but it is pure science - good article from Edmunds Scientific at https://www.edmundoptics.com/knowledge-center/application-notes/lasers/an-introduction-to-optical-co....
Glass coating is a sophisticated and highly automated process, but any sophisticated process can have failures. Even the highest end printer (which is a much simpler device than those used in coating lenses) needs maintenance and proper adjustment and QC monitoring. Thus the more complicated lens coating machines would need even more attention and maintenance and be more susceptible to bad batches due to some anomalous condition. Delamination could be caused by improper glass preparation, equipment out of calibration, contamination of deposition materials, clean room contaminants, or a host of other variables.
In other words, there is a lot that can go wrong with any batch of coated glass. It sounds like Canon may have recognized a bad lot of coatings for the front element of this product in Japan. if so, they have not recognized the same for products destined for the US. I very much doubt that there is a "Japan" and "US" product line in the factory for coating glass. I suspect all of the front elements for this product are made in the same room and on the same machine or machines for both the US and Japan. So IF Canon, Inc has recognized there was at least one bad batch of glass sold in Japan it seems plausible the same could certainly be true for the same glass destined for the US market.
So yes, maybe it was applied wrong, as you say. The onus in the US is on the customer to demonstrate this. One way is for enough product that was not ill-treated to have to be replaced at the factory. Canon is still not obligated to admit an error in manufacturing. It is usually much better if they do so, of course. Canon could perhaps be more sensitive to their reputation in Japan than in the US, or it could simply be that there is not a "smoking gun" pointing to a manufacturing defect and there has been in Japan. I will assume the latter, but I certainly understand for those affected it may be harder to do so.
If I were in their shoes and the rumor of replacement in Japan is true I would certainly be raising the issue here and via any other means that I thought appropriate to get a proper resolution. I hope this works out well for both Canon and the people with delaminated coatings.
>> Owns/Owned both Canon EOS mirrorless full-frame and APS-C cameras and associated RF, RF-S and EF adapted lenses - inventory tends to change on short notice. Same for flashes, tripods, bags, straps, etc.
Plus>> Canon imagePROGRAF PRO-1100 Printer
>>The opinions and assistance are my own. Please don't blame Canon for any mistakes on my part.
