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10-04-2014, 08:43 PM   #1
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Automatic focus on a K-3 - definitive guide?

I am delighted with my K-3 but am having trouble really understanding the various Autofocus options and frankly find the manual useless. I realise that this may be covered in parts on a number of threads but here's my question.

Is there anywhere - in this forum or elsewhere - that gives a complete and understandable account of how to use all the many options in the K3 autofocus system?

For example, what does it mean to have all these focus points? Why is this such a good thing (it's just confusing to me!)?

What is best for landscape photography - I'm guessing not AF-C?

What is best for portrait - single point on the eyes, I imagine, but then what happens if the subject moves?

As you may have realised by now, you're dealing with a beginner here. I jumped straight from an early iDSL to the K3,so I've never had any previous experience with such a complex system - which I'm sure is excellent, if you understand it.

10-04-2014, 09:12 PM   #2
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Not definitive but here is some information.

I generally use center point, AF-S. More from habit than anything else. However, that mode is still very reliable and useful for just about anything that is not moving.

Next is AF-S with select AF point, I resisted using this for a long time, but I am finding it more and more useful as I practice with it. Yes you can focus and recompose using the center point but sometimes selecting a particular point just works better. I am using it a lot with tabletop work, camera is on the tripod so moving the selected AF point around allows the composition to remain static.

Then we have AF-C which is used for things that are moving, dogs, birds planes, whatever. I rarely shoot anything that moves so I do not use this much but I can say it is much improved over the AF-C in the k-5. I have a user mode set up with this for bird in flight or anything that I happen upon that is moving.

One other trick I am using is setting focus to the rear AF button instead of the shutter release. Then put the camera in AF-C. A single press to focus of the AF button acts much like AF-S but hold the AF button down and you have AF-C, that's as flexible as you can get.

I'm sure someone with more technical details will jump in but that's rather simple explanation.
10-05-2014, 02:44 AM   #3
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@jatrax: just one question concerning the AF-C mode. You mentioned that you set up a user mode - so I'm just curious which other settings you changed and saved under this user mode. (Because otherwise it would be more simple just to switch the lever from AF-S to AF-C ?)


Edit: of course the small lever is on K-7, while in case of K-3 you have to push the AF mode button and turn the front wheel - so then it might really be easier to simply change to U1?

Last edited by zzeitg; 10-05-2014 at 07:16 AM.
10-05-2014, 05:19 AM   #4
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QuoteOriginally posted by zzeitg Quote
@jatrax: just one question concerning the AF-C mode. You mentioned that you set up a user mode - so I'm just curious which other settings you changed and saved under this user mode. (Because otherwise it would be more simple just to switch the lever from AF-S to AF-C ?)
JTrax gave a great explanation. But the one I think is the most important is to change your focus button to the rear AF button and not use the shutter button for focusing, this is what the pros do. For now center point using the rear focus button will be the most helpful Just focus on the eyes or closest eye if the head is turned to the side and adjust your composition. If you are using an extremely shallow depth of field like in macro or with an F1.8 or faster changing the focus point is the better way to go since recomposing may put your most important area out of focus. However for normal portrait or landscape work recomposing should work great. Also with landscape you will mostly be working with much smaller Fstops like F8 or greater so just focus and recompose

10-05-2014, 08:47 AM   #5
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QuoteOriginally posted by zzeitg Quote
You mentioned that you set up a user mode - so I'm just curious which other settings you changed and saved under this user mode. (Because otherwise it would be more simple just to switch the lever from AF-S to AF-C ?)
I use this mode for bird in flight so settings are:
TAv
ISO auto 100-3200
SR = on
AA filter = Off
WB = sunny
First frame AF = focus priority
Action AF = focus priority
Hold AF = medium
Focus point = 27 point select with center point selected
Shooting mode = continuous high
Shutter speed = 1/640
Aperture = f/4

I do not do a lot of BIF so maybe others would have more experience and better choices but this is what I use. It gives you a quick setting in case that bald eagle with a common murre in it's talons flies by and you don't want to totally muck up the shot like I did.

10-05-2014, 11:05 AM   #6
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thanks for details of your setting...


few questions:
- WB - do you find this setting important? Isn't it OK for most situations to simply keep AWB?
- shutter speed / aperture - I guess with these settings you really need "sunny" conditions with lot of light, otherwise the photo will be simply too dark. Is there a reason why not to stay in "P" mode and let the camera decide?
10-05-2014, 12:24 PM   #7
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QuoteOriginally posted by zzeitg Quote
- WB - do you find this setting important? Isn't it OK for most situations to simply keep AWB?
For BIF I find a fixed WB to be better as you are panning and the camera may read the scene differently from shot to shot. For nearly all other situations I use AWB. And on k-3 maybe it is not such a problem as AWB on k-3 is better than previous cameras.
QuoteOriginally posted by zzeitg Quote
- shutter speed / aperture - I guess with these settings you really need "sunny" conditions with lot of light, otherwise the photo will be simply too dark. Is there a reason why not to stay in "P" mode and let the camera decide?
Mode setting is TAv so camera will adjust the ISO to make the exposure. Priority for BIF is keeping the shutter speed as high as possible. 1/640 is really too slow and those settings are just defaults for the user mode, I then adjust to what to the situation requires.

My 'BIF' user mode is intended to get me settings that will allow a decent FAST shot of something moving. Lot's of changes required per the actual situation for the best set up, these are just so I get some kind of results.

A hard lesson from the photo above. Wrong settings in almost every way and potentially a shot of a life time. The one posted is the best of a dozen I snapped, none are worth anything but I was in the right spot right time and totally unprepared. That won't happen again.
10-05-2014, 12:41 PM   #8
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This might help you a bit:
https://www.pentaxforums.com/forums/172-pentax-k-3/251413-post-your-k3-af-settings-here.html
Why don't you cross-post there as well?
A little searching sometimes helps !


Last edited by jpzk; 10-05-2014 at 12:46 PM.
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