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12-10-2018, 11:02 AM   #1
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Live View Auto Focus issues?

Using the 50-200mm with the K70 and noticing a significant difference in live view and OVF auto focus speed. Catches on quickly using OVF but much slower with LV, sometimes hunting for seconds in good light with clear subject? Similar with 50mm prime so can't be the lens. Anyone else experienced anything similar?

12-10-2018, 11:07 AM   #2
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Live view is always slower when auto focusing.
12-10-2018, 11:22 AM   #3
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QuoteOriginally posted by Mark1961 Quote
Using the 50-200mm with the K70 and noticing a significant difference in live view and OVF auto focus speed.
CDAF (live view) is intrinsically slower, though potentially more precise/accurate than PDAF (used with optical viewfinder) where speed is deemed more desirable than other factors. Short answer = it's supposed to be that way.


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12-10-2018, 11:23 AM   #4
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QuoteOriginally posted by sergysergy Quote
Live view is always slower when auto focusing.
only on the K3? Never noticed as much a difference on other cameras including the K5, which overall had poorer AF?

12-10-2018, 11:26 AM   #5
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All the pentax models I have had behaved this way
12-10-2018, 11:43 AM   #6
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QuoteOriginally posted by Mark1961 Quote
only on the K3? Never noticed as much a difference on other cameras including the K5, which overall had poorer AF?
The K-5 has slow optical focus and even slower live view focus. The K-3 has faster optical focus, while live view is still slow, so it feels like there's a bigger difference in the 2 modes.
12-10-2018, 12:59 PM   #7
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QuoteOriginally posted by Mark1961 Quote
Using the 50-200mm with the K70 and noticing a significant difference in live view and OVF auto focus speed. Catches on quickly using OVF but much slower with LV, sometimes hunting for seconds in good light with clear subject? Similar with 50mm prime so can't be the lens. Anyone else experienced anything similar?
On my KP PDAF {method used with OVF) is faster than CDAF {method with LV} in 'normal' light.
When I took a photo that required ISO=12800
First photo with KP - PentaxForums.com
the CDAF took a couple seconds to creep up to "in focus", but it was never clear to me when PDAF got there.

Last edited by reh321; 12-10-2018 at 07:57 PM. Reason: rewording
12-10-2018, 01:54 PM   #8
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FYI: CDAF = contrast detect auto focus; PDAF = phase detect auto focus
Generally, cameras OVF uses phase while LV uses contrast detect!

12-10-2018, 03:29 PM - 1 Like   #9
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QuoteOriginally posted by reh321 Quote
he CDAF took a couple seconds to creep up to "in focus", but PDAF didn't get there at all.
Do you have the AF assist lamp enabled in your settings and not blocked by a finger or two? Even without the lamp, your KP's PDAF is sensitive to -3 EV100 which computes to hard to see anything for my eyes and should have acquired focus at least as easily as the CDAF.


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12-10-2018, 06:30 PM   #10
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QuoteOriginally posted by stevebrot Quote
Do you have the AF assist lamp enabled in your settings and not blocked by a finger or two? Even without the lamp, your KP's PDAF is sensitive to -3 EV100 which computes to hard to see anything for my eyes and should have acquired focus at least as easily as the CDAF.
I have reworded my comment. After many years of manual focus, I don't quite trust AF, certainly not with a new camera. I don't remember exactly how long it took PDAF to turn on the "focus" light, but I could never see that it was in focus, which is why I switched to LV while the cats slept on. My point in response to the OP was that CDAF was slowish but sure, and the advantage of PDAF seems to be diminished as the scene gets darker.
12-10-2018, 09:08 PM   #11
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QuoteOriginally posted by reh321 Quote
My point in response to the OP was that CDAF was slowish but sure, and the advantage of PDAF seems to be diminished as the scene gets darker.
Definitely.


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12-10-2018, 09:37 PM   #12
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If you want really good live view AF speeds, get the 55-300mm PLM. Other non-screwdrive lenses, as well as lenses with a shorter focus throw, should also be better.

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