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06-12-2018, 08:40 AM   #16
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QuoteOriginally posted by bdery Quote
The Irix is a very good solution, I really liked testing it, it's dependable but not quite as high-quality. It's often decentered (but repaired by the manufacturer under warranty) and suffers from pretty strong field curvature. It's not AS sharp as the Pentax 15-30 but for the money you're getting a lot.
It's not even decentering. I saw the same problem on a trip and upon closer inspection I noticed that it's actually the mount's screws that became loose. I tightened them however I could and when I came back from the trip I did it again with some medium thread locker.
The problem is a shoddy design! The Pentax design uses five screws to hold the bayonet ring on to all of their lenses, even the lightweight DA Zooms. I checked all my adapters and extension tubes, and they are all five screw, too. But the HEAVY Irix has just three screws! Even Samyang/Rokinon/etc. have four screws, and I've never had problems with those. Sigma uses three screws too, but those are mostly plastic and lightweight. They would break rather than become unscrewed.

Well, problem solved. No recurrences so far. Been a few months.
My only gripe is that this also affects the weather sealing since the seal can't make full contact against the camera mount and this happened during a trip to a rainy canyon and I did shoot in the rain.
I should also note that the lens had prior taken a fall mounted on a MZ-S. The lens survived unscathed. The camera and camera mount didn't. So that could have been the reason it became loose.
If it's any worth, I do use the lens quite often and do think it's an excellent piece of gear in every aspect.

Here's a shot from my replacement MZ-S I bought from a forum member here.

Gesendet von meinem Mi A1 mit Tapatalk

06-12-2018, 09:43 AM   #17
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QuoteOriginally posted by torashi Quote
The problem is a shoddy design! The Pentax design uses five screws to hold the bayonet ring on to all of their lenses, even the lightweight DA Zooms. I checked all my adapters and extension tubes, and they are all five screw, too. But the HEAVY Irix has just three screws! Even Samyang/Rokinon/etc. have four screws, and I've never had problems with those. Sigma uses three screws too, but those are mostly plastic and lightweight. They would break rather than become unscrewed.
All things being equal, more screws are better, however you can't simply equate less screws with a shoddy design. As you said, simply using threadlocker solved the problem. If the screws are strong enough there's no need to have so many of them at all cost.
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