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09-02-2018, 03:23 PM   #1
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Pentax K3 II autofocus Issue

Hi! I was shooting with my Pentax K3 II at an air show recently and couldnít get the camera with a Pentax DA 18-250mm zoom to lock in the focus. It was continuously hunting no matter what setting it used.
The atmosphere was heavy with a combination of clouds and soft sun. After getting home I was testing the camera and it seemed to focus without any difficulty. I was wondering if the low contrast conditions while shooting the show would have caused the camera to hunt so much?
In setting different AF mode it didnít make any difference. i thought that the spot setting would have secured a lock onto the subject. I have not searched my manual to see if there are any suggestions.
Appreciate if anyone has a similar experience or if I somehow wasnít using an appropriate setting.

09-02-2018, 04:07 PM   #2
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My K-3 sometimes doesn't focus when I start at a position where focus is actually very close to in focus (with a screwdrive lens).
If this happens and my intended subject is near infinity I focus something close (the ground in front of me) and then re-focus my subject or vis-ŗ-vis depending where my subject is.
09-02-2018, 04:53 PM   #3
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QuoteOriginally posted by TommyRingo Quote
a combination of clouds and soft sun. After getting home I was testing the camera and it seemed to focus without any difficulty. I was wondering if the low contrast conditions while shooting the show would have caused the camera to hunt so much?
It is likely, As I have had the same experience trying to get a shot of an Osprey flying overhead on an overcast day using my KP which is normally pretty good about that. That seems to happen with my Sigma 120-400 and my 55-300 PLM. Were you using single focus point or 9 or max? There is a chart someone created with initial settings for best results in different situations that lists the preferred settings. I think airshows are 9 point and I don't remember the metering settings.
09-02-2018, 06:29 PM   #4
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I find it can do that if the front element of the lens is a bit dirty or dusty and there is some sunlight. Presumably the dust can produce scattered light that interferes with AF. A quick clean usually improves the situation.

09-03-2018, 06:41 PM - 1 Like   #5
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QuoteOriginally posted by SSGGeezer Quote
It is likely, As I have had the same experience trying to get a shot of an Osprey flying overhead on an overcast day using my KP which is normally pretty good about that. That seems to happen with my Sigma 120-400 and my 55-300 PLM. Were you using single focus point or 9 or max? There is a chart someone created with initial settings for best results in different situations that lists the preferred settings. I think airshows are 9 point and I don't remember the metering settings.
Thanks, SSGGeezer!
I agree that this is the most likely explanation. I didnít find the day I was shooting that changing the AutoFocus Mode (# points made any difference). I plan to find a similar situation (overcast, etc) to see if I can replicate the air show situation and confirm why it couldnít get a focus. One thing I did do that day was to switch to manual focus and was able to get a few good shots.
Thanks again, TommyRingo
09-06-2018, 02:01 PM   #6
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QuoteOriginally posted by SSGGeezer Quote
It is likely, As I have had the same experience trying to get a shot of an Osprey flying overhead on an overcast day using my KP which is normally pretty good about that. That seems to happen with my Sigma 120-400 and my 55-300 PLM. Were you using single focus point or 9 or max? There is a chart someone created with initial settings for best results in different situations that lists the preferred settings. I think airshows are 9 point and I don't remember the metering settings.
PLM seems to be far more prone to that issue than the Sigma 100-300 F4 (which is essentially similar to the 120-400) - noted when trying both lenses on the K-3 & k-3 II at an airshow earlier this year.
09-06-2018, 02:28 PM   #7
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Some things to consider: in low contrast situations, especially with slower (aperture) lenses, any dust and etc will affect the ability to lock focus. For example, the 55-300 will hunt more than the 50-135 in the same low contrast shooting (my experience).

Also, if you haven’t done so, take a rocket blower to the mirror box of your camera. A bit of dust on the AF module has a huge impact.
09-06-2018, 07:28 PM   #8
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QuoteOriginally posted by twilhelm Quote
Some things to consider: in low contrast situations, especially with slower (aperture) lenses, any dust and etc will affect the ability to lock focus. For example, the 55-300 will hunt more than the 50-135 in the same low contrast shooting (my experience).

Also, if you havenít done so, take a rocket blower to the mirror box of your camera. A bit of dust on the AF module has a huge impact.
Thanks for the tip on blowing the mirror to clean the AF sensor! As I would have been focusing at full zoom (250mm) any dust would be interfering more.

09-07-2018, 01:44 PM   #9
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QuoteOriginally posted by SSGGeezer Quote
There is a chart someone created with initial settings for best results in different situations that lists the preferred settings. I think airshows are 9 point and I don't remember the metering settings.

does anyone know where I can find it?

Thank you
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