SDM Lenses

Started Sep 30, 2009 | Discussions thread
awaldram
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High Speed SDM
In reply to awaldram, Oct 2, 2009

All this talk of SDM failure got me doing a quick functional test of my SDM glass.

I was surprised to find my 50-135 end to end travel is now .9 secs

When purchased (nearly 2 years ago) the same travel was 1.3 secs

My 16-50 returned the same figure for end-to end as it did when purchased (12 months)

Now I don't generally bother about end to end travel as it has limited effect on achieving AF lock in the real world, But .9 to 1.3 is massively different.

The figure is not scientific and it could be battery condition etc.

But the biggest likely cause IMHO is that I use the 50-135 almost constantly and the 16-50 occasionally so the WS have loosened up on the 50-135 allowing faster transit times with less load on the motor.

From this I surmise that users, most risk, are new purchases (likely to be dead from new or shortly afterwards. and occasional snappers who will pull their SDM lens out of the cupboard after 9 months to find it seized.

 awaldram's gear list:awaldram's gear list
Pentax Q Pentax K-3 Pentax smc DA* 55mm F1.4 SDM Pentax smc DA* 16-50mm F2.8 ED AL (IF) SDM Pentax smc DA* 50-135mm F2.8 ED (IF) SDM +11 more
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