Discussion in 'Back Room' started by New Daddy, Dec 31, 2013.
Should I need to rent, you just earned my business. You are an important asset to this forum.
When two materials interface, the softer of the two will wear. This is true for metals of course, but for a metal to plastic interface, there is only one winner - no prizes for guessing. This doesn't mean failure, just that the plastic mount will wear gradually from day one, resulting in increased play at the interface.
Very informative. I worked for a camera retailer for many years and sold both metal and plastic mount lenses. Other than appearance, I don't think the plastic were any less reliable. If the lens mounts were indestructable, it would result in many more broken camera bodies.
...that pop you heard....was the bubble in my fantasy world...gee thanks
This is certaintly true - although with the latest polycarbonates, this will take a lot longer to happen than it used to. I will say this: If I do have an accident while the lens is mounted on my camera, I personally would prefer that the lens mount breaks off cleanly rather than bending, taking much of the lens and/or camera innards with it.
That's a fair point and a plus for a sacrificial plastic mount (I think we should refer to them as engineering polymers, not plastics).
What is the mechanism for that? Wear is caused by friction. If there is no relative motion between parts there will be no wear. I can't see any reason to expect the plastic on the inside of a lens mount to wear and cause slop. If the bayonet is plastic, then that would wear when the lens is installed and removed from the camera.
But the fact is, there have been several examples of early catastrophic mount failure with the Olympus 12-40mm lens. That might or might not be due to a poor design decision, or it might or might not be due to a manufacturing fault. But it is real and it is happening.
"Olympus 12-40mm not fragile by the industry standards" is not what Lens Rentals said:
"Much of the recent internet rioting was triggered by some Olympus 12-40 lenses that broke off at the plastic mount. Several people reported their lenses broke at the mount with minimal force applied (a short fall or even pressure from other items in a camera bag). I can say we ship those lenses all over the country and they seem no more likely to break than any other lens we stock. But apparently at least some of them had a weak mount.
What amused me was the absolute fury expressed by numerous photographers that a “professional quality” lens might have a plastic mount. I’ve looked up the term ‘professional quality’ everywhere and nowhere have I found it defined as ‘having an all-metal mount’. But some people are livid that it isn’t so. If you’ve read one of these posts on the internet lately, you’ve learned all kinds of things. . . none of which are true."
I don't think the failure is down to a plastic/metal interface, it's screwing the mount into plastic ( from what I've read).
Replace professional quality with inappropriate material selection. Olympus may well be good at optical design, servo control, but they don't seem to be too hot with mechanical design. Anyone worth their salt would not design like that.
Thank you to the OP, we should make this thread required reading for all contributors to the 'ouch' thread? The quote I remember is 'that you convict beyond reasonable doubt' whereas in the discussion with the 12-40 there has been a tendency 'to convict with unreasonable certainty'
Not to mine it's not
A few lenses have broken. Some more may yet break. Perhaps with the fullness of time this will turn out to be a real issue or a silly mob panic. In the meantime I continue to use my 12-40 with the same realization as I use all of my other lenses - it hasn't broken, it probably won't, but if it does, I'll deal with it then. At this point it's a non-issue to me. This article reinforces this approach. If it breaks someday, I'll get it fixed. Until then I use it like any other lens, with no special provisions to prevent breakage.
...and this is exactly the type of statement Roger was referring to. Irony is alive and well, it seems
At no point during the article does Roger mention having opened up a 12-40mm lens. It's basically saying that the use of structural plastics is not uncommon even amongst larger and more expensive lenses. Whether there is a design, manufacturing, or assembly related issue on a few, some, or all copies of 12-40mm lenses is still unknown. Haven't heard of any more breakages though so fingers crossed they were isolated events.
It is reassuring that Lensrentals has been sending copies of this lens all over the place without incident to date:
Having worked in manufacturing for most of my working life I would comment that fixing metal parts to engineering grade plastics using thread forming screws is nothing new.
Yes I've seen failures like the photographs before and they are quite often due to a combination of factors rather than just one. For example:-
1 The hole in the mouldings is close/ on top design limit on one impression/tool.
2 The moulding tool was not quite up to temperature and the first few of a batch are slightly different to the rest/approved product.
3 The moulding powder was not pre-treated properly.
4 A batch of screws were on bottom design limits of diameter and/or length.
Please note - None of the above are "design" flaws or errors.
It might take three of the above before a lens "fails" when stressed. If the probability of each one is say 1% (0.01) then you might see 1 in 1,000,000 fail. You are unlikely to find this out during product development.
Obviously 1 and 4 above can be checked physically and or slight corrections made to eliminate them but 2 and 3 are much more difficult to trace. I would suspect that Olympus is not going to say anything during the investigation ( if at all going by most Japanese company's ethos).
Without being involved with the process of investigation it's impossible for any of us to state the reasons why. But if I was a betting man ( I'm not) I would be looking at 2. given the level of failures.
Yes it may be possible to make the area stronger ( e.g. deeper holes with longer screws) but I think the question is what do Olympus do when people have any failures - hopefully we will find out over the next few weeks as lenses get repaired/replaced.
His point was that we keep getting sidetracked by irrelevant stuff. He never said the 12-40 wasn't fragile, in fact he said:
"Obviously a few Olympus 12-40mm lenses have broken at the mount. It may be there was a batch of badly molded mounts. It may be a design flaw. It may just be random chance – a few of everything break. But it’s not just because the mount is plastic."
He is saying that even though "Obviously a few Olympus 12-40mm lenses have broken at the mount", its not simply because the mount is plastic. He defending plastic mounts, not the lens.
I can totally understand owners of this lens being invested into thinking the breaks are an anomaly (and I hope they are), but the insistent and not always logical ways people rush to defend this lens and the issues we have seen is bizarre. Honestly, I'm beginning to think Steve Jobs reality distortion field was amateurish compared to Olympus.
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