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12-23-2013, 04:43 AM   #1
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AF Area: SEL L vs SEL M vs SEL S

It would be interesting to know the situations where using one AF Area is better than using another. For example wouldn't using L provide the maximum tracking capability? If so - why not always use SEL L?

12-23-2013, 07:12 AM   #2
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Hi Rob:

Unfortunately since acquiring the K3 winter has sent in so not any opportunities to test tracking. My feeling is that it will take lots of testing to work out the best combo for different situations.

Dale
12-23-2013, 09:05 AM   #3
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Depends on what your subject matter is. Too many focus points can be confused by changing patterns of action if many human bodies are your subject. OTOH a single centered focal point my be too inflexible in the same context, requiring the shooter to constantly recalibrate focus.

Many points may work better on a large railroad train running on a track which keeps things predictable.

What is your usage scenario?

M
12-23-2013, 11:16 AM   #4
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Two primary environments - wildlife/birds in flight/eagles AND grand kids playing sports. Appreciate your insight and help Miguel - thanks.

12-23-2013, 11:47 AM   #5
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My pleasure Bob.

We are shooting similar subjects. I think a factor in the preferred AF area to use depends on how much the subject fills your frame and how erratic the subjectís movements are. So if you are photographing an eagle flying away from a bare tree branch and you can see its eyes, then Iíd recommend using the center point. Their flight pattern is fairly stable, and not too fast (unless they are diving for food, lucky you), so by pressing the AF button in synch with its arc of movement you should have a sharp enough shot.

If I find birds to be isolated enough to be able to stick a single AF point on them, I can maintain this with surrounding helper points. It helps to have a 300-400mm lens. It helps even more to learn bird behavior again and again.

Kids sports, however, pose other challenges. A lot depends on whether the individual sporting event allows for the framing of isolated individual action or if participants are mostly part of a moving hive. Baseball is more of the latter and its action can be predictable. You can anticipate that collision at home, or how the pitcherís windup will fill your frame. For this you want center-point AF; Iíve had shots of the pitcher turn out badly because the multipoint AF somehow decides to fixate on the third baseman nervously moving some behind.

Kids soccer and lacrosse can be tougher because things are moving semi-randomly and quickly. As noted in other threads, Iíve been fairly happy with the 9-point AF for soccer on the K-3, but Iím still experimenting. With my Canon 7D I am just about always using a center point AF with four surrounding helper points.

As with birds it depends how close you are to the action. Iím always on the sidelines or on the line behind and to the side of the goal. If you are shooting as a spectator from the stands, then the AF margin of error is a lot less intense due to the distance away.

M
12-23-2013, 01:22 PM - 1 Like   #6
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When using AF.C to get tracking I am using SEL L, SEL M, or SEL S. My understanding is that all these modes use a single point to acquire focus and you can move this point round within the selected area.. So for birds in flight, say a solitary eagle, I am guessing that SEL L, using all the focus points for tracking and I generally select the center point as the target focus point. Up to now, only about a months with three or four sports outings, I have also used SEL L for kids sports - soccer and flag football. I am going to have to try using SEL S (nine points) with the center. I did see another post recommending SEL M but setting the focus point down, rather than in the center, which would mean focus point would fall at the belt level of a player being tracked.
If I just use center point I feel I would be giving up tracking capability in AF.C - Is this correct? If so then for tracking the choice might be limited to SEL L or SEL M or SEL S.
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12-23-2013, 01:38 PM   #7
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QuoteOriginally posted by RockvilleBob Quote
....
If I just use center point I feel I would be giving up tracking capability in AF.C - Is this correct? If so then for tracking the choice might be limited to SEL L or SEL M or SEL S.
It depends how you define tracking. It will still keep the lens in focus and will track the subject's movement towards and away from you but will not track it in lateral movement. It would in other words be plain AF.C though some people still call that focus tracking. I don't.
12-24-2013, 05:23 AM - 1 Like   #8
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QuoteOriginally posted by RockvilleBob Quote
When using AF.C to get tracking I am using SEL L, SEL M, or SEL S. My understanding is that all these modes use a single point to acquire focus and you can move this point round within the selected area.. So for birds in flight, say a solitary eagle, I am guessing that SEL L, using all the focus points for tracking and I generally select the center point as the target focus point. Up to now, only about a months with three or four sports outings, I have also used SEL L for kids sports - soccer and flag football. I am going to have to try using SEL S (nine points) with the center. I did see another post recommending SEL M but setting the focus point down, rather than in the center, which would mean focus point would fall at the belt level of a player being tracked.
If I just use center point I feel I would be giving up tracking capability in AF.C - Is this correct? If so then for tracking the choice might be limited to SEL L or SEL M or SEL S.
Read up on 1st frame action as this should make it clear when to use different expansion areas.

in short the first frame action will pick the primary from 9,25 or 27 points respectively.
If your target is in a crowded environment it may be impossible for the camera to match AF with what you think your shooting at without additional help (narrow scope)

limiting expansion to 8,24,or 26 should help.

24,26 seems a limit of technology rather than sensible options.!

12-24-2013, 06:08 AM   #9
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Thanks for the response. I guess for a clear subject, like an eagle flying, the larger area would work and for a busy scene a smaller area would be a better selection. The K-3 represents a first time exposure for me into all the autofocus options. The manual leaves much to be desired. The only explanation of 1st Frame Acton in Pentax material is this (I will need to look for Nikon and Canon explanations):
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12-24-2013, 09:50 AM - 1 Like   #10
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I found this article about autofocus on the Internet and felt it gave me a good place to start. Just posting it in case others also find it of value
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File Type: pdf DSLR Autofocus Modes Explained.pdf (2.40 MB, 668 views)
12-24-2013, 06:00 PM - 1 Like   #11
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I have two user modes set up, one spot focus and metering, the second 27 point afc, with center weighted metering. The only reason I can think that one would limit the point count is to prevent wrong selection in low contrast low light situations.

It is mostly very dark here right now, so I'm using the center point focus for accuracy. Multiple point has a tendency to jump around to wrong points if they are all close on the focus plane, or low contrast. With better light it works very well.

I'll probably have a firmer opinion by summer next year.
12-25-2013, 06:55 AM - 1 Like   #12
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I posted a thread on my experiences with AF-C. Here's an excerpt:

- I intend to leave menu items 16 and 17 on focus priority at all times. I have no use for OOF shots.
- Line 18, Hold AF, I will stay with Low as default, until I know better how it works.
- Focus point choices will depend on what I'm shooting. It is damned hard to keep a fast bird in the center, so I will use all the points. Focus points are not a big issue with a truck.

For tracking to work, you have to ensure that the first shot is locked on your target. If the first shot locks on anything other than the subject, it will not let go and you will have a string of misses.


Read more at: https://www.pentaxforums.com/forums/172-pentax-k-3/245959-k-3-tracks-oncoming...#ixzz2oUifDCcZ

I haven't shot sports yet, but I intend to try center point with 9-point expansion, AF Hold on Low. I suspect I may need to bump up the AF Hold.
07-30-2014, 03:57 AM - 1 Like   #13
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A very useful guide to advanced auto-focus that I have looked at quite often is from Canon, for their pro-sports shooter the EOS 1Dx. Many of the K-3 AF options resemble those of the 1Dx:

Canon DLC: Article: Master the EOS-1D X's AF System

The Guidebook is a 55 page PDF available for free download (12MB).

This is another good Canon article, specifically on using multiple AF point modes:
http://www.learn.usa.canon.com/resources/articles/2012/5d3_multiple_af_points.shtml

Last edited by rawr; 07-30-2014 at 04:08 AM.
07-30-2014, 04:18 AM - 1 Like   #14
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QuoteOriginally posted by rawr Quote
A very useful guide to advanced auto-focus that I have looked at quite often is from Canon, for their pro-sports shooter the EOS 1Dx. Many of the K-3 AF options resemble those of the 1Dx:
This demonstrates a significant weakness in Ricoh/Pentax: the incorporation of significant technical improvements in high-end models without sufficient white papers or tutorials explaining how it works. Look at the paltry amount of space in the K-3 manual devoted to explaining the AF options, how the AF tracking uses the AE sensor block and how it uses contrast, shape, colour and subject distance to separate the initial subject from other foreground subjects or background objects.

I wonder if this applies to all markets or just the non-Japanese markets.

Dan.

Last edited by dosdan; 07-30-2014 at 04:29 AM.
07-30-2014, 07:07 AM - 1 Like   #15
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QuoteOriginally posted by dosdan Quote
This demonstrates a significant weakness in Ricoh/Pentax: the incorporation of significant technical improvements in high-end models without sufficient white papers or tutorials explaining how it works.
I agree wholeheartedly. The K-3 has so many features that appear to target specific use cases, but the documentation is simply not there.


Steve
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