July 26, 2014, 05:15:49 AM

Author Topic: Quality control issues with the 24-70 L II?  (Read 4906 times)

neuroanatomist

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Re: Quality control issues with the 24-70 L II?
« Reply #15 on: September 19, 2012, 07:48:35 PM »
Anybody know if they focus via live-view for these tests (I would hope so)? It would be weird relying on the AF of the camera, so I am 99% sure they do use live-view.

From TDP:

"Tests are conducted using externally-magnified Live View manual focusing and center-point-only autofocus. The best of the many re-focused shots (typically at least 10 sets - often 15-20) are used for the results for each camera/lens/focal-length/aperture combination. The proper lens hood is in place for all test shots, all filters are removed. Image Stabilization, if available, is turned off."
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Re: Quality control issues with the 24-70 L II?
« Reply #15 on: September 19, 2012, 07:48:35 PM »

LetTheRightLensIn

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Re: Quality control issues with the 24-70 L II?
« Reply #16 on: September 19, 2012, 08:35:17 PM »
Anybody know if they focus via live-view for these tests (I would hope so)? It would be weird relying on the AF of the camera, so I am 99% sure they do use live-view.

From TDP:

"Tests are conducted using externally-magnified Live View manual focusing and center-point-only autofocus. The best of the many re-focused shots (typically at least 10 sets - often 15-20) are used for the results for each camera/lens/focal-length/aperture combination. The proper lens hood is in place for all test shots, all filters are removed. Image Stabilization, if available, is turned off."

Keep in note:

1. they did not do that on their earlier tests, they were much less careful earlier on
2. despite the above they still get weird things some apertures suddenly going to junk, maybe it's just mixed up files now and then, but for some reason they seem to only ever get bad copies of tamron

kaihp

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Re: Quality control issues with the 24-70 L II?
« Reply #17 on: September 20, 2012, 02:40:28 AM »
Quality standards are not reduced over time, but the number of units getting a major inspection off the line can decrease. In order to maintain efficient throughput in manufacturing, not all aspects of the assembly are inspected at 100%.
While statistical testing is the norm in many companies (and the only thing making sense in many cases), the QC procedure do depend on the type of business you're in. I work for a medical device company, and we do 100% inspection (all units are tested). Most electronic products like mobile phones are 100% tested as well.

heptagon

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Re: Quality control issues with the 24-70 L II?
« Reply #18 on: September 21, 2012, 02:54:51 AM »
For the price of L-Lenses, Canon should do 100% testing. Especially early in the production.

TDP usually does a pretty good job in testing lenses so i guess that the second lens really shouldn't have been sold.

serendipidy

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Re: Quality control issues with the 24-70 L II?
« Reply #19 on: September 21, 2012, 03:44:36 AM »
+1000!!

Why should it be a lottery to get a decent quality lens from Canon? Those with experience maybe can detect the less than ideal copies and send them back. The casual hobbiest may not and just be stuck thinking that's the best they can do. Also, when someone sends several less than razor sharp new copies back, to say B&H or Adorama, until they find one they like, what happens to those returned copies? Are they sent back to Canon or resold?
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Viggo

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Re: Quality control issues with the 24-70 L II?
« Reply #20 on: September 21, 2012, 03:58:53 AM »
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
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heptagon

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Re: Quality control issues with the 24-70 L II?
« Reply #21 on: September 21, 2012, 10:48:37 AM »
@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.

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Re: Quality control issues with the 24-70 L II?
« Reply #21 on: September 21, 2012, 10:48:37 AM »

Studio1930

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Re: Quality control issues with the 24-70 L II?
« Reply #22 on: September 21, 2012, 11:08:22 AM »
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
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Mt Spokane Photography

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Re: Quality control issues with the 24-70 L II?
« Reply #23 on: September 21, 2012, 05:09:00 PM »
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.

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Re: Quality control issues with the 24-70 L II?
« Reply #23 on: September 21, 2012, 05:09:00 PM »