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02-10-2010, 11:04 PM   #16
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QuoteOriginally posted by aaronius Quote
But I just feel strange that my KX will be slower in AF compared to my old Nikon D80 which is old technology.
Actually, that is not strange at all. At the risk of spamming again, that same guy posted speed tests of the k-7 with kit lens (pretty fast focusing lens for Pentax) vs. a 19 year-old film camera with an 11 year-old kit lens, and they were about the same speed, so I am not surprised that you feel your D80 is faster than your k-x.

[YT]http://www.youtube.com/watch?v=7-gfkUJA6dY[/YT]



SAFOX is just slow doggone it. Many of us have been whining about it for years (not just Rice High). Hopefully, the next generation of Pentax DSLR will have new AF algorithms. Replacements for SAFOX and SDM could make Pentax a pretty potent competitor in performance. I really hope we see improvements like these in Pentax's next generation, as opposed to colors for the k-7, and more in-camera postprocessing gimmicks.

02-10-2010, 11:25 PM   #17
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QuoteOriginally posted by PentaxPoke Quote
SAFOX is just slow doggone it. Many of us have been whining about it for years (not just Rice High). Hopefully, the next generation of Pentax DSLR will have new AF algorithms. Replacements for SAFOX and SDM could make Pentax a pretty potent competitor in performance.
My guess why the system is slow, is precisely because the Pentax phase detection/rangefinder readings are inaccurate, especially in low light. In the video you posted, the first reading (on the Pentax) is way off, so it does have to check again and focus again.

EDIT: Here's an example, where the Canon has to focus again, as well (because the first reading was wrong):

[yt]http://www.youtube.com/watch?v=E-TPzui2Oxs[/yt]


QuoteQuote:
I really hope we see improvements like these in Pentax's next generation, as opposed to colors for the k-7, and more in-camera postprocessing gimmicks.
Same here.

Last edited by asdf; 02-10-2010 at 11:36 PM.
02-10-2010, 11:28 PM   #18
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Guys can advise if using C-AF will help the KX autofocus faster (hunt less) if I am taking performances and events?
02-11-2010, 01:02 AM   #19
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QuoteOriginally posted by asdf Quote
My guess why the system is slow, is precisely because the Pentax phase detection/rangefinder readings are inaccurate, especially in low light. In the video you posted, the first reading (on the Pentax) is way off, so it does have to check again and focus again.

EDIT: Here's an example, where the Canon has to focus again, as well (because the first reading was wrong):
Interesting theory. It would be quite interesting to know the details of the algorithm. I wonder why the control cannot be accomplished continuously while the focus ring rotates. What is the reasons for the pauses in between motion? Also, why can't the pauses be shorter? The details are all probably proprietary though.

aaronius, I don't thing AF-C will improve speed. It is designed to continually refocus if the subject moves. I think you may be happier with AF-S. In fact, I prefer the AF-S setting even for moving subjects, but that is my personal preference.

02-11-2010, 01:19 AM   #20
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QuoteOriginally posted by PentaxPoke Quote
Interesting theory. It would be quite interesting to know the details of the algorithm. I wonder why the control cannot be accomplished continuously while the focus ring rotates. What is the reasons for the pauses in between motion? Also, why can't the pauses be shorter? The details are all probably proprietary though.
If you take a look at the video of focusing with the AF assist lamp, you can notice that the Canon and Pentax AF assist lamp flashes 2 or 3 times; after the first flash, the ring moves and after it stops, there's another flash. So in each case, there were two or three rangefinder readings. And I don't know how continuous-AF varies from camera to camera--and whether it's really continuous. Perhaps, someone else can tell us...
02-11-2010, 01:52 AM   #21
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Oh man, I do find it unfortunately slow in low light! I missed some birthday shots of my girlfriend (blowing out candles with lights off) since it wouldn't focus fast enough ha, contrarily her dad with a Nikon D70 got em. Both of us using our respective kit lens.

Oh well! I need a better low light lens!

-Jay
02-11-2010, 08:03 AM   #22
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QuoteOriginally posted by aaronius Quote
Guys can advise if using C-AF will help the KX autofocus faster (hunt less) if I am taking performances and events?
I would actually consider that to probably not be the best idea. Probably better to keep it on S-AF, locked into one specific known focus point (center, most likely), and feather the shutter button to keep it refocusing when the subject moves.
02-11-2010, 08:05 AM   #23
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QuoteOriginally posted by er1kksen Quote
I would actually consider that to probably not be the best idea. Probably better to keep it on S-AF, locked into one specific known focus point (center, most likely), and feather the shutter button to keep it refocusing when the subject moves.
Oh you mean like AF-A does.

02-11-2010, 09:17 AM   #24
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No. With AF-S, it only refocuses when you tell it to. With AF-A, lets say the subject suddenly moves laterally but the subject distance doesn't change. Suddenly the focus point is over something in the distance, but the actual subject is still in focus.

AF-S? You're good, just keep your finger on that shutter button. The focal distance is locked in.

AF-A? It focuses on whatever the focus point is on, in this case- not the subject.
02-11-2010, 10:36 PM   #25
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Thanks for the advices guys, think I will just stick with the AF-S for the time being. I only used AF-S when I was using Nikon last time so I am fine with it. I do hope that Pentax will improves their AF system in future cameras, that will make Pentax from being good to being great!
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