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11-02-2013, 12:17 PM   #16
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This looks good to me. I occasionally shoot cyclists and they are a good test for any AF system. The speeds are relatively high and the subject fairly dynamic. These head on shots are great and up to current market standard for AF-C, but I would be interested in seeing some done with the cyclists coming around a corner. I.e. lateral movement as well as changing distance, say with/without fixed focus point.


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11-02-2013, 12:50 PM   #17
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This is good news... The Tour de France goes though my home town next year (yes I'm in England)
11-02-2013, 01:30 PM   #18
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I think this bodes very well for the AF-C.

The examples here are very good because the test conditions are very demanding on the AF system.

The subjects are moving at or close to perpendicular to the focus plane. This causes constant changes in focus plane distance, and they happen at the fastest rate for the speed the subject is moving. Horizontal panning shots are much less of a challenge to AF tracking because the subject is moving closer to parallel to the focus plane.

A very fast max aperture tele lens was used. Max aperture matters because the AF system focuses with the lens wide open. The shallower DOF requires more AF correction per delta distance. Slower lenses require considerably fewer adjustments for a given change in distance so provide less of a challenge. Also, by using a wide aperture for exposure, DOF covers fewer focusing errors.

The subjects are being captured at medium to close distances. Closer working distances mean constantly shallower DOF and require more movement of the focusing mechanism for a given change in distance. Look at any lens. As working distance decreases, the # of degrees of focus ring rotation per distance change increases, so the AF system must move the focusing group farther and more often with shorter working distances.

Nicely done, to both Winder and the K-3!

Scott
11-02-2013, 01:39 PM   #19
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Hmm.... Looks promising, doesnt´t it?

11-02-2013, 01:40 PM   #20
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QuoteOriginally posted by stevebrot Quote
This looks good to me. I occasionally shoot cyclists and they are a good test for any AF system. The speeds are relatively high and the subject fairly dynamic. These head on shots are great and up to current market standard for AF-C, but I would be interested in seeing some done with the cyclists coming around a corner. I.e. lateral movement as well as changing distance, say with/without fixed focus point.
I agree that these indicate that the new AF system is up to current market standard for AF-C, but lateral movement as well as changing distance is probably as much of a test of the photographer's technique as it is of the AF system. With the Expanded AF area feature, this will probably prove to be better also.

Scott
11-02-2013, 01:57 PM   #21
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Very nice. My test will be my dog running towards me. The K-5 maybe got one shot in focus, as well as all over the place metering. This is promising.
11-02-2013, 02:02 PM   #22
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QuoteOriginally posted by innivus Quote
Thanks! The actions shots with the new AF are (for me, anyway) the single biggest reason to upgrade to a k3. It seems the last image of some groups tend to be out of focus - is that the AF or have the passed the minimum focusing distance of the lens?

Keep 'em coming!
Looks like the shirt stays in great focus, the face less so. Will face-AF work on people wearing dark shades? I hadn't tried that.
These look very promising, maybe some day I will be a bird-in-flight shooter but it hasn't happened just yet.
11-02-2013, 02:32 PM   #23
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Thanks for posting and doing the work. This looks very good and I bought the K-3 primarily for improved AF. It looks like a good decision. I have a feeling the DA*300 will still be a little slow due to the lens design but the Sigma Zooms I have 70-200 and 150-500 should really benefit. I would be interested in the feedback of experience with the Sigma 500 and K-3 - I am guessing that will be a stellar duo.

11-02-2013, 02:39 PM   #24
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QuoteOriginally posted by jimr-pdx Quote
Looks like the shirt stays in great focus, the face less so. Will face-AF work on people wearing dark shades? I hadn't tried that.
These look very promising, maybe some day I will be a bird-in-flight shooter but it hasn't happened just yet.
As the hanlde bars are also focused the blured face is most lilkle a result of the 1/500 shutter, not related to AF at all.
11-02-2013, 03:23 PM   #25
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Great shots. What lens is this? It wasn't clear to me in the exif.
11-02-2013, 03:28 PM   #26
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QuoteOriginally posted by virtualjsk Quote
Great shots. What lens is this? It wasn't clear to me in the exif.
Everything posted was shot with the Sigma 85mm F/1.4.
11-02-2013, 03:58 PM   #27
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QuoteOriginally posted by Winder Quote
Everything posted was shot with the Sigma 85mm F/1.4.
I sense the Sigma lenses have robust focus mechanisms, if not robust at least fast.
11-02-2013, 04:02 PM   #28
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QuoteOriginally posted by RockvilleBob Quote
I sense the Sigma lenses have robust focus mechanisms, if not robust at least fast.
The Sigma 85mm is not slow, but its moving a lot of glass and its not the quickest of lenses.
11-02-2013, 04:05 PM   #29
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A useful set of tests and good results.

QuoteOriginally posted by Winder Quote
I used the center AF point and on the last shot I was on his chest, not his face. Did not have as much luck with the 9 center AF points
I suspect single centre point AF is not the best option for AF-C tracking.

In the Canon 1Dx AF settings User Guide, which is 1Dx focussed but a good guide to sports AF-C settings generally, they say:
QuoteQuote:
However, since Spot AF reads such a small area of the scene, it's not really suited to fast-moving subjects
One of the K-3's 'Expanded Area AF' or 'Zone Select' options may work better. They seem very similar to the 1Dx's 'AF Point Expansion' mode options.

Pentax need to put out a book on the new AF features. They have a lot of nuances, I suspect.
11-02-2013, 04:31 PM   #30
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Thanks for sharing!! The Tracking seems pretty darn good - I have a date in June marked on the calendar... 8 more months for me.
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