*ist DS AF speed

[Patrice LACOUTURE (GMail)]

Hi dear PDMLers,

My apologies in advance if this topic has been discussed at length 
already, however I couldn't find it in my PDML archives.

Like many people around, I've always found that the *ist DS focuses 
quite slowly in poor lighting conditions.

But last week-end, I took my MZ-5n out of its disgrace, and put on my 
F-50 f/1.7. I didn't have this lens yet when I bought the *ist DS, and 
had never used it before with the MZ. I must say I was immediately 
impressed by the AF speed!

In both low light and normal light conditions, the MZ focuses way faster 
than the *ist. It's not just noticeable, it's like twice as fast!!! I 
wish I had such raw speed on my *ist!

I used NiMH AA cells on both the MZ and the *ist DS. I assumed maybe the 
*ist DS draws more power for electronics, so I tried lithium batteries: 
it's a bit faster, but still not on par with the MZ still equipped with 
its NiMH cells.

Is the *ist DS supposed to be so slow, or is my unit somehow bogus and 
I've failed to notice so far? Do any of you have an experience to share 
in this regard?

My unit is still under guarantee for a few months, so I'd rather have it 
fixed now if it's abnormal...

Best regards

Patrice