Lens quality control

Started 7 months ago | Discussions thread
parallaxproblem
Veteran MemberPosts: 4,607
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Re: Sample variation is not that big a deal
In reply to ProfHankD, 7 months ago

ProfHankD wrote:

From what I've seen, sample variation is larger on newer autofocus lenses than on old manual lenses. This makes sense in that motor drive for focus, etc., requires less friction and somewhat looser fits. The older lenses also tend to have fewer and all spherical elements, which also help.

However, I think a lot of what's going on also has to do with the modern practice of designing tooling to "wear through" a tolerance range. The machinery may be capable of tighter tolerances than things made years ago, but this ability is used to control placement of values so that they vary within the allowable tolerance range for the longest possible time without needing frequent (or 100%) testing/readjustment to confirm things are still in tolerance.

In any case, relax. As usual, LensRentals is right that the out-of-spec lenses stand out against the normal variation, and normal variations often trade one aspect for another rather than being one good vs. one bad. Don't use the out-of-spec lenses and things will be fine. The reason there are design tolerances is because the designer and manufacturer analysis said that within that range things work well enough... which they generally do.

Hum...  have you ever bought an SEL16/2.8 ?

I wouldn't feel 'relaxed' about QC when buying that lens at all

Howver I think there is another factor at play here: offshoring

I simply don't believe that 'quality systems' ensure standardisation...  the easiest way to confirm this is to eat in a few different McDonald restaurants in your neighbourhood (if you can stand it).  You will find that the burgers do not taste the same in each restaurant, and McDonalds has spent years trying to ensure standardisation of it's products (and assembling a hamburger is much easier than assembling a lens!)

Take a product that has been built in an established factory with a history of high-quality production and a workforce that takes pride in its activity, and move it to a developing nation where you recruit from scratch the cheapest workforce possible (why move if it isn't to pay the least salaries possible?) and the quality of output will simply *not* be the same whatever processes you put in place.  Add cultural factors into that and you create even more problems - I lived and worked in Thailand for a while and I love the country and count many Thais amongst my closest friends, but the 'work ethic' there is simply not the same as that in Japan or in Germany.  My friends in Vietnam would always ask me to buy European-built Nokia phones for them even though they cost much more than the Chinese assembled items as they simply didn't trust them, and were always highly sceptical of anything manufactured locally.

The most annoying thing about offshoring is that it causes a lot of misery amongst those directly impacted, but it normally doesn't actually save any money once the 'unforseen factors' are accounted for - as witnessed by prices for the latest Thai-built Sony lenses that exceed those of the Japanese-built Sigmas, and which are higher than the cost of equivalent Japanese-built lenses 15 years ago.  Sometimes production costs actually increase or the company discoveres that local corruption or communications problems etc simply make it impossible to produce goods there...  in my last job the order from the CEO was to 'offshore jobs' and so the managers actually had to pay more money to engage people in other countries than they would if they had kept the jobs locally (and redundancy payments, training costs and service interruption added further to these costs!)

However the person who suggested the offshoring in the company has normally already received their bonus by the time the consequences are obvious, and by then it is too late

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