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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?

MartinsB wrote:

awaldram wrote:

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 !

How did you calculate that?

7+7+4+6 =24 years with 1 failure 24/1 = 24

Calculating MTBF
MTBF sounds simple: the total time measured divided by the total number of failures observed. For example, let's wring out a new generation of 2.5-in. SCSI enterprise hard drives. We run 15,400 initial units for 1,000 hours each (thus our tests take a little less than six weeks), and we find 11 failures. The MTBF is (15,400 x 1,000) hours/11, or 1.4 million hours. (This is not a hypothetical MTBF; it represents current drive technology in 2005.)

http://features.techworld.com/operating-systems/1944/mtbf-what-lifespan-can-you-expect/?intcmp=ros-md-acc-p-ft

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