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05-16-2013, 06:04 AM   #1
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auto focussing with K5 and 300mm DA* f4

I have had a 300mm DA* for a short time, with my K5. I have noticed that the auto focus struggles when shooting birds low overhead (i.e. they fill a substantial portion of the field) against a sky background (with plenty of light). I would have thought that the contrast of the bird's outline profile against the sky is ample for easy AF.Whether it is the angle of elevation of the lens, and whether it's just my lens, I'm not sure. I don't have the same problem with my other AF lens, which is the 18-55mm kit lens.

Has anyone had this problem?

Cheers, Andrew

05-16-2013, 06:36 AM   #2
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It might be that the AF sensor can't find contrast in the bird, or mayve the bird is moving too fast for the AF to lock. You did say that it happens when they fly low over you, ie. relatively close to the camera.
05-16-2013, 06:38 AM   #3
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Based upon my experience with the DA* 200 (with a similar AF system):

The narrow field of view provided by telephoto lenses together with the proximity of the bird means that the image will move rapidly over the AF-sensor. That can be a challenge for any AF system. You will have to excersize panning your camera together with the bird (unless you are already doing that?).
05-16-2013, 06:45 AM   #4
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Are you using the afc, continuous focussing? Center point focus? With both of them and practice at panning so that the bird stays in the center of the viewfinder, it should focus.

If the bird is low overhead it means that everything is happening quickly, so it may simply be that the lens/body focus mechanism can't react quickly enough.

05-16-2013, 06:56 AM   #5
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If the bird are low overhead filling the frame of a DA*300 ! What are they doing? Dive-bombing you? I'd get outta there before you get pooped on.

Sounds pretty challenging for any AF system esp if the subject (underside) is in shadow.
05-16-2013, 07:20 AM   #6
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I usually don't have too many problems with the DA* 300 and the K-5.

Are you using 11 point AF, 5 point or centre-spot? The contrast you describe may only be relevant if there is a AF sensor within the vicinity of a contrasty area, which may not always happen even under 11 point AF if the edge of the bird is right out to the image boundary.

Also I have to add - I hope you aren't using any UV filters, and are always using the hood. Both may play some role in the performance of the lens when shooting into the light as you describe.
05-18-2013, 03:37 AM   #7
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Thanks

Thanks All for the tips - I'll do a bit more experimenting and report back.
05-18-2013, 08:26 AM   #8
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QuoteOriginally posted by Andrew Crouch Quote
Thanks All for the tips - I'll do a bit more experimenting and report back.
Make sure your firmware is up-to-date and consider turning OFF SR (shake reduction).

Also, consider getting a copy and spend a little time learning LR (Lightroom), plus NIK's plug-in collection for LR (NIK offers excellent free on-line tutorials for each module... I use Define for noise reduction, Vivesa to expand dynamic range, Output Sharpening, and Color Efex Pro to adjust lighting.).

A little quick and dirty (I spend no more than 3 minutes on an image ) post-process fine tuning can help a lot.

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