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10-30-2010, 10:45 AM   #1
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Video of K-5's LiveView AF

While browsing around YouTube, I saw this Japanese sales video on the Pentax K-5. What caught my eye was a demonstration of the LiveView AF out in a scenic area. If you're wondering how the AF performance is in LiveView, this should really please you. Jump to 0:58 for the AF demo:

[YT]http://www.youtube.com/watch?v=_-uDwtaitVQ#t=0m58s[/YT]

- Jason

10-30-2010, 03:38 PM   #2
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Need to remember that the video only show LV focus in CONTRAST mode which my experience with on the K5 so far is lukewarm. In PHASE mode it is more accurate in low light but blacks out the LCD while it drops the mirror, focuses and re-flips the mirror up. I have not tried the "Smiling Face" mode yet.....no one smiles when they see me.
10-30-2010, 04:01 PM   #3
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QuoteOriginally posted by imtheguy Quote
Need to remember that the video only show LV focus in CONTRAST mode which my experience with on the K5 so far is lukewarm. In PHASE mode it is more accurate in low light but blacks out the LCD while it drops the mirror, focuses and re-flips the mirror up. I have not tried the "Smiling Face" mode yet.....no one smiles when they see me.
Lukewarm, ok maybe - but compared to what? I would love to see another dslr that does a better job (micro 4/3 does not count). Maybe the Sony slts (not maybe, definitely - but not technically a dslr), but pentax has done a pretty good job in his dept, definitely a huge step from their own previous iterations.
10-30-2010, 04:16 PM   #4
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QuoteOriginally posted by pxpaulx Quote
Lukewarm, ok maybe - but compared to what? I would love to see another dslr that does a better job (micro 4/3 does not count). Maybe the Sony slts (not maybe, definitely - but not technically a dslr), but pentax has done a pretty good job in his dept, definitely a huge step from their own previous iterations.
Just comparing Contrast to Phase on the K-5. Both have drawbacks/advantages. At least on my K-5, the Contrast AF misses by a mile enough that I can't trust it, or at least have to try it a 2, 3, 4 times and check the best of the group. I am not talking about candlelight but normal room with lamps testing with a black tripod leg on a beige carget. Also shade, picking the tree trunk out from the background lawn, also shaded. Certainly would never use it for serious landscape shots but for faces I would give it a shot. As I said the Phase AF is fine but for the 3 second blackout. I have no experience with this kind of comparison on any other DSLR so my expectations and methods COULD be way off.

10-30-2010, 04:20 PM   #5
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QuoteOriginally posted by imtheguy Quote
Just comparing Contrast to Phase on the K-5. Both have drawbacks/advantages. At least on my K-5, the Contrast AF misses by a mile enough that I can't trust it, or at least have to try it a 2, 3, 4 times and check the best of the group. I am not talking about candlelight but normal room with lamps testing with a black tripod leg on a beige carget. Also shade, picking the tree trunk out from the background lawn, also shaded. Certainly would never use it for serious landscape shots but for faces I would give it a shot. As I said the Phase AF is fine but for the 3 second blackout. I have no experience with this kind of comparison on any other DSLR so my expectations and methods COULD be way off.
Wow that's somewhat disappointing...
I was really hoping to use live-view AF to overcome slower lenses with my AF TC rather then conventional AF, but now I'm not sure its going to work at all...

Also can you explain the difference between Phase and contrast AF?
10-30-2010, 06:00 PM   #6
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QuoteOriginally posted by imtheguy Quote
I have no experience with this kind of comparison on any other DSLR so my expectations and methods COULD be way off.
Contrast AF on the 7D locks on every time, just takes a little bit. Sounds like the K-5 doesn't take the time and just rushes to try and get done focusing. Phase sounds like Quick mode on the 7D which uses the normal AF system. It's super fast. I don't use it purely because just adds more wear to the shutter. Contrast locks on everytime.
10-30-2010, 06:10 PM   #7
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QuoteOriginally posted by pxpaulx Quote
Lukewarm, ok maybe - but compared to what? I would love to see another dslr that does a better job (micro 4/3 does not count). Maybe the Sony slts (not maybe, definitely - but not technically a dslr), but pentax has done a pretty good job in his dept, definitely a huge step from their own previous iterations.
I have a sony R1 from year 2005. It is not DSLR but APC cam, it does AF using contrast detect. If you get chance try this cam, it is very very fast You will be surprised. (At least 100 times faster than anything of contrast detect of my k-x) .
10-30-2010, 07:42 PM   #8
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QuoteOriginally posted by JohnBee Quote
Wow that's somewhat disappointing...
I was really hoping to use live-view AF to overcome slower lenses with my AF TC rather then conventional AF, but now I'm not sure its going to work at all...

Also can you explain the difference between Phase and contrast AF?
Autofocus wikipedia

John, the difference is described in section 4. I wish I had a tc to run some testing for you! Theoretically I do think that contrast detect could be better than phase for something like the 50-135 and tamron 1.4x tc with sdm. My thought on that possibility being that the focus is found using contrast at the pixel level, which should not be limited by whatever it is that causes the hunting with the sdm/tc combo. Of course, someone will need to try it in order to find out!

10-30-2010, 07:46 PM   #9
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is the K-r's Liveview speed similar to k-5's?
10-30-2010, 08:10 PM   #10
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QuoteOriginally posted by JohnBee Quote
Wow that's somewhat disappointing...
I was really hoping to use live-view AF to overcome slower lenses with my AF TC rather then conventional AF, but now I'm not sure its going to work at all...
I must backtrack a little here. My original informal test was at long focal lengths even though I used a very clearly defined subject. I just tried again with the trusty da16-45 under normal incandescent lighting and this time contrast AF worked just as well and a little faster than the phase AF.

Tomorrow I will retry the original 2 lenses I had trouble with (da*300/4 and da18-250) to see what is making the difference. There is hope yet JohnBee! I will try a lens+1.7x AF TC to force a high minimum aperture so John can get his answer too about slow lens plus AF TC.
10-30-2010, 10:11 PM   #11
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QuoteOriginally posted by JohnBee Quote
Wow that's somewhat disappointing...
I was really hoping to use live-view AF to overcome slower lenses with my AF TC rather then conventional AF, but now I'm not sure its going to work at all...

Also can you explain the difference between Phase and contrast AF?
Phase detect AF uses the same AF hardware which is used for Viewfinder work.
Contrast detect uses the Live-View image feed directly - the same way P&S cameras do AF.

On the K-7, Phase detect is usually faster and more accurate in good light.
The advantage of Contrast detect becomes very apparent in failing light.
Typically SAFOXVIII AF starts to lose speed and accuracy dramatically in failing light before shutting down altogether. CD makes use of the sensor's High-ISO boost capability to get a brighter image during AF and lock AF even in lighting where SAFOX VIII PD would have given up.

CD is slow on the K-7, a lot faster it seems on the K-5.
My K-5 won't be delivered until late November , so I'll have to wait a while more to check it out...
10-30-2010, 11:51 PM   #12
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Hi,
I don't understand very well. AF works alone when you are recording or you need to do it by yourself like with the K-7?
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10-31-2010, 01:01 AM   #13
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I still cannot get over the Live View AF speed on this leetle beastie...it is amazing!!
10-31-2010, 02:52 AM   #14
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QuoteOriginally posted by imtheguy Quote
At least on my K-5, the Contrast AF misses by a mile enough that I can't trust it
QuoteOriginally posted by imtheguy Quote
I must backtrack a little here. My original informal test was at long focal lengths even though I used a very clearly defined subject. I just tried again with the trusty da16-45 under normal incandescent lighting and this time contrast AF worked just as well and a little faster than the phase AF.

Tomorrow I will retry the original 2 lenses I had trouble with (da*300/4 and da18-250) to see what is making the difference.
One of the advantages of Contrast AF (CAF) is that it should be more precise than phase AF, and with the K-7 it is most of the time. What you report is a real bummer. It needs further invesitigation.

However, when you say you had problems in particular at longer focal lengths: Contrast AF depends on the subject being static. It must not move while you focus. Otherwise, the internal assumptions of the CAF are violated and most CAF algorithms are still at their infancy to deal with more complex situations. Therefore, at 300 or 250 mm, hand shake should be bad enough to confuse CAF. Please, redo your comparsion using a tripod and show us 100% crops from the focussed region, for contrast AF and phase AF, resp. Thank You.
10-31-2010, 06:26 AM   #15
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QuoteOriginally posted by Malsi Quote
Hi,
I don't understand very well. AF works alone when you are recording or you need to do it by yourself like with the K-7?
Regards.
Malsi
Sounds like you are referring to af during video recording. There is still no af during video recording on the k5. This discussion is talking only about af while using the liveview feature.
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