Roger and Aaron at Lensrentals.com decided to do a teardown of the brand new Canon EF 70-200mm f/4L IS II after having one return from a rental with a malfunctioning IS unit. Don't worry about the reliability of the IS unit, as its the same one that Canon uses in its newer lenses and has proven to be very reliable.
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Roger discovered after doing MTF testing on a batch of the EF 70-200mm f/4L IS II lenses, that the copy variation was the lowest he'd ever seen for a zoom lens. Canon's manufacturing abilities are obviously on display here, though they'll never go public with how they're assembling lenses now, but there are usually some clues in tear downs.
Lensrentals.com speculates:
We have some hints, and a lot of Roger speculation, about how Canon is getting lenses with such low variance. Here’s what we know: Canon has more optical adjustments than most lenses, not less. So while they may have tighter tolerances (I have no clue), the key seems to be more in a careful optical adjustment of compensating elements than anything else.
Adjusting compensating elements is time-consuming and can be complicated. We sometimes spend half a day doing it on a complex lens. Canon seems to have made the process modular and logical. In this lens, for example, there are (we think):
– Centering for the focusing element.
– Tilt and centering adjustments for one or more middle elements
– Centering adjustments for the rear element.
It is clear that Canon is going with more, and more straightforward, adjustment of optics than the other manufacturers. Most lenses have a centering, or at most a centering and tilt adjustment. Many lenses have no optical adjustments at all. There are a couple of non-Canon lenses that have multiple adjustments, but it’s the exception, and often the adjustments are shims, which have more limited adjustment possibilities. See the full teardown
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Of course Roger and Aaron and all others at Lensrentals know, what they're doing, but just to imagine doing this on your own... phew!
Thanks for doing and sharing that with us, guys.
In the discussion about the 70-200/4-MFT-Testing Roger said, that he will perhaps not do Variance-measurements in case of the 70-200/2.8 III:
"I haven't tested it; since the optics didn't change I don't expect to see a difference. I wouldn't be surprised if the variance is smaller. Reality is it's a week long commitment of me and a very expensive machine to do a full set of 70-200 lenses for variance and it's just lower on my priority list right now."
Just like teams have their armchair quarterbacks, who'd win every game were they ever on the team, Canon has its armchair CEOs, engineers, etc. Without ever trying or even touching a product they declare it a winner or loser before the coin has even been tossed. Before it even reaches store shelves they begin to moan. They'll do the same when mirrorless is announced. In fact, they are already doing it.
Leica has been having optical and mechanical reliability problems for the past few years, at least
My experience of shooting with Canon gear in rugged environments (nature, birding, wildlife) in a nutshell is that Canon generally delivers quality, Nikon does not anymore, unfortunately. We have both an extended Canon and Nikon gear, and with Nikon we had a lot of trouble, dying camera mechanics, dying AF drives, failing camera buttons and thread mount contacts because of worse weather sealing. With Canon I only had a broken thumb wheel of my original 7D during the past 10 years, that's it. I am no fanboy, that's just our side-by-side real world experience. This reliability and quality is what keeps me to use Canon (plus Canon's nice color rendering just out of the camera). So my own experience fits well to what I read at lensrentals (I don't care anymore about dpreview & Co.).