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12-30-2007, 10:17 AM   #31
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QuoteOriginally posted by GaryML Quote
The real value of forums like this one is to share real-life experiences that go beyond what a magazine tester (or a guy with a Web site, like Klaus) can discover in a one hour or one day test. Using the camera system for seven months and taking thousands of photographs gives you more information on how the camera system works for you than any published review can provide.
And here's the difference between Klaus and other tester. Klaus did not spend just one hour. He has spent many many hours with each system as he has to test the lenses day-in day-out. And it is not restricted to studio/indoor test pattern either. He actually went out and use the camera.

Anyways, my comment is not just specifically directed to you even though it is a reply to your post. I am just addressing the general notion that "Pentax AF Sucks". It does NOT. Maybe particularly the AF tracking is a bit weak. But in general photography, Pentax AF system is right up there with the best.

12-30-2007, 11:08 AM   #32
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QuoteOriginally posted by Ishpuini Quote
I actually compared my DA*50-135/2.8 to my Sigma EX70-200/2.8, which is generally considered a fast AFfing telezoom. Indeed the Sigma travels in slightly over half the time from nearest distance to infinity. However, that time takes it from 1,8m to infinity, whereas the DA*50-135 starts at 1m. The 1,8m mark on the DA*50-135 is half way its travel, so when measuring the time it takes to travel from 1,8m to infinity it is actually faster than the Sigma!!

I think we should be comparing to similar lenses, rather than to primes or standard zooms... If you do that the DA*50-135 isn't that slow at all. Except when it hunts, then it does take more time, but that's solely related to its starting at 1m already...

Just another way of looking at things...

That's interesting and true, the focus is more than fast enough if you go from 2,5m to infinity and most of the full travel time is taken to go from 1m to 2,5m.

Maybe that's why Canon incorporates a limiter that goes from 2,5m to infinity (AFAIK) to cut the AF time on their 70-200f2.8...

I did a lot of tracking shots yesterday (my 4 years old coming towards me on its bike in bright sunlight) and, while AF-C doesn't struggle to keep up with the action, the shots end up being slightly back focused if one uses f2.8. Of course, stopping down the lens to f8 gets you almost all shots in acceptable focus but then blurring the background is difficult.

Predictive AF should be better implemented in future Pentax cameras, especially if higher frame rates are introduced.

Actually, a higher frame rate should mean faster mirror/shutter mechanism and lead to better "predictive" AF since it will cut the lag between focus and picture taking and should automatically reduce the amount of backfocusing.

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