Pentax Quality Control Strikes Again

Started Apr 23, 2015 | Discussions thread
DAVID MANZE Veteran Member • Posts: 5,768
Re: Pentax Quality Control Strikes Again

awaldram wrote:

Jim King wrote:

awaldram wrote:

You perhaps are not aware how manufacturing works in the modern age

The only reason 'occasional' lens are checked is to ensure the lens are coming off the manufacturing line within 'acceptable defined limits. It has nothing todo with checking the lens itself (it doesn’t get a 'checked' stamp)

There I agree wholeheartedly with you!

Manufacturing plants use designs and build technique to achieve a set quality .... they then randomly check the plant is hitting that quality.

This doesn't mean things can't go wrong but is unlikely and even it it does not for an appreciable run before detected.

I don't think it's a problem with a production run as such, the problem is mostly with the couplets and triplets which cemented together the cement takes a while to set and the top elements "float" out of true, speaking to both Sigma and Tamron service department they both stated they were waiting for parts, when I enquired "what parts" they said the couplets, I probed further and they both blamed the out of alignment couplets to be the problem with my lenses. I phoned a Sigma a while later and was told the parts had arrived , a week later my lens was returned and was perfectly centered, the same was the case for Tamron decently centered.

The company I work for has a 2% limit for failing memory simms , One of the manufacturers we 'badge' has a 5% limit consequently we QC every simm from this manufacturer so that we can deliver on our 'promise' with our label.

The same applies to Joe even though it's manufacturer to user, Pentax obviously have a lower standard than Joe therefore the only way Joe can be sure to get 'what he requires' is to test every lens he buys, As his standard is greater than the manufacturers a good proportion will fail his test.

I'm not sure why we are always saying that "only Joe" has very demanding standards, don't we all when paying out $500 or much more for a lens? at least we would like a well centered lens, I know for the most part I insist on it at least to the point within 1/2 stop, that to me is acceptable. I've had F2.8 lenses where at F11 they still didn't resolve the out of balance plane of field. (Tamron 17-50mm/ Sigma 50-150mm both F2.8) The incidence of decentered lens I've purchased is frightning frankly, the latest is the (Tamron 150-600) I've just had notice a new one is on it's way.

This is because as designed they were never meant to pass his test hence he needs the better ones off the production run rather than average.

Pentax on the other hand couldn't care less they set their 'standards' to keep returns and warranty repairs to an acceptable level and if they can put two milk bottoms on a pepsi can and sell it for £1000 with low return they will.

To assume otherwise shows a level of brand blindness that is the true 'fanboy state' to believe Pentax make lens as a service to their users rather than make money !!! and leads to the disillusioned rants we often see in these forums ..... hell has no fury like pentaxian spurned

Andrew, wouldn't you expect to something close to a standard distribution of "quality" around the center point of the design spec, with outliers and and beyond the edges of the spec? if so, even if Joe's acceptance criteria are higher than Pentax's limits, I would think that he would still see a good proportion of acceptable lenses, with a few outliers. Instead, most of the lenses he gets seem to be unacceptable to him. Either his standards are absurdly high (and I don't think this is the case), his testing methodology is faulty, or he has had an extreme run of bad luck...

Your thoughts?

I would agree and honestly don't know why Joe suffers such high failures.

Probably because like me he checks his lenses, once bitten twice shy, a lot of folks find out a lot later on. Actually if you read Photozones reviews you will find Klaus Schroiff is "always complaining about de-centered lenses" (especially Sony's) often needing up to three copies to find a decent one, I think it would be hard to argue with his expertise.

I trust Joes testing so when he says a lens is d-centered I'm confident it is (at a level that easily users see-able)

I trust his findings because they equate with mine! I noticed already a few complaints of decentered DA 16-85mm copies in the very short time of their production. Photozone will be testing this lens soon!

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A fanatic is one who can't change his mind and won't change the subject.
- Sir Winston Churchill
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A fanatic is one who redoubles his effort when he has forgotten his original aim.
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P.S. Love that quote BTW.

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