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What does a Screwdrive Converted Pentax DA* 50-135mm F2.8 lens sound like?

Started Jun 8, 2014 | Discussions thread
awaldram
awaldram Forum Pro • Posts: 13,271
Re: What does a Screwdrive Converted Pentax DA* 50-135mm F2.8 lens sound like?

candgpics wrote:


So, "once your SDM fails, which is inevitable" is correct in spirit, I think, and a good and appropriate warning to potential customers, even if it really will not happen in every instance, or even most.

DA* 16-50 7 years old no failure

da* 55 4 years old no failure

da* 300 6 years old no failure

da* 50-135 7 years old failed at 4 years was replaced

That gives an MTBF of 24 years !

If you take all available stats and translate them into 'failure' rate you get

da*55 = 3-5%

da*300 = 2-4%

da* 50-135 = 8-10%

da* 16-50 = 8-12%

The industry 'mean' is 2-4% so though the first SDM lens have higher than average for the industry they also are within tolerance for a new technology at release and one would expect if you limited the data used to recent years they would now be within except able limits.

Though it easy to rant 'those bxstards with their crappy SDM' when you have a failed unit the facts are different and show why Pentax/Ricoh have not and will not take any action to fix web mythology rather than real facts.!

SDM is more prone to failure than screw drive but so is HSM/USM etc etc.

SO the correct statement would be in the unlikely event your SDM fails !

To imply that SDM failure is inevitable or even probable is foolish an the facts do not support it.

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