Quality control issues with the 24-70 L II?

[Viggo]

You'll see MUCH bigger variation out in the field when you're using phase-AF, and even then you'll probably hardly ever notice it in a real shooting situation.

Besides, apertures can vary alot, and there is VERY few lenses that follow the "soft open, better one stop, very good two stop down and diffraction softens at f22"- curve. For example the 50 L is sharper at 1,8 than at 2,2.

And the 24-70 mk2 is no different and it still is the best zoom ever, but it's when a test charts shows you a slight difference it's a bad copy and it sucks and Canon should burn in hell.

I like my lenses to be optimized as well, and I have had several copies of every lens (never saw a difference) and I adjust them with AFMA, now lately, with the best method, FoCal. They are adjusted as good as they can be on the best AF-body ever made, and that's good enough for me.

Perfect phase-AF is a myth.

http://www.lensrentals.com/blog/2012/07/autofocus-reality-part-1-center-point-single-shot-accuracy

 

[heptagon]

@Viggo: Yes, Phase-AF is a big problem. But Lensrentals found out that New Cameras with New Lenses can have a very good phase-AF. (Look for part 2 or 3 of the story)

However, what the test of the two lens samples shows are much bigger variations. Other manufacturers are even worse than that. Maybe Tamron gets tested 3 times and the worst is used while for canon it's the best sample.

For the new lenses it gets harder and harder to achieve near-perfect manufacturing because the tolerances required to achieve the high quality results get lower and lower. This is not an easy problem to overcome. Lensrentals are the only site which sometimes tests a number lenses from one batch. They could provide some numbers on the rate of bad lenses per model. Other sites which only test a few samples cannot provide conclusive evidence on how high the rate of bad lenses is.

 

[Studio1930]

Samples 1 and 2 are very close when you look at the 24mm shots. This is the exact reason the newer camera bodies have AFMA for both near and far on zoom.

Also some good reading here...

http://www.lensrentals.com/blog/2011/10/the-limits-of-variation

 

[Mt Spokane Photography]

Unfortunately, lenses can be damaged during handling and shipping, and can, of course, be improperly assembled.
QC inspection went away years ago for most Japanese companies, its a obsolete process. It was replaced by Total Quality Management which goes far beyond just inspecting finished products like they did 20 years ago.