Maybe its a Focus Accuracy Issue

rawr · 07-03-2013, 01:52 PM

Originally posted by nomadkng

do any of you have a "technique" to compensate?

FWIW, I've found that you can also 'train' the AF to work with difficult scenes by engaging the AF in short bursts, rather than holding the AF button down continuously before a shot. Running the AF in short bursts seems to give the AF algorithms a more precise feel for the features of the subject, so the AF doesn't run right across the range from zero to infinity.

Assigning AF only to the AF button on the camera back can also sometimes help with the process of exercising more control over the AF and your shooting. Many people swear by the AF button.

Just on the centre-focus point, since you have taken the time and effort to test for back and front focus, shot some focus charts etc, perhaps now you can also do some testing to identify the sensitivity boundaries around your centre-focus point... Setup a contrasty object (tennis ball? soccer ball? checkers board?), place it a working distance away against a neutral backdrop, and explore it with the camera AF in centre-point AF-S, monitoring the green hexagon to see when it lights up or not as you move across the focus target. UnknownVT did something like this with his K-x some time ago, using a simple pencil set up on a fence, and it was a good illustration of how precise even the K-x's centre-point could be.

It's also worth rehashing the point that if you want to depend on the AF, and need to shoot wide-open all the time on lenses other than less than 50mm, the narrow DOF will oftentimes kill you as much as any AF sensor blunders.

Anvh · 07-03-2013, 02:00 PM

like RAWR says the AF button works very well, expecially with quickshift or HSM lenses. Je focus manually close to the subject and then turn on the AF for the last part.
Almost 99% of the time it will lock onto the subject, since it's the sharpest and closest subject.

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07-03-2013, 01:52 PM	#16
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	Originally posted by nomadkng do any of you have a "technique" to compensate? FWIW, I've found that you can also 'train' the AF to work with difficult scenes by engaging the AF in short bursts, rather than holding the AF button down continuously before a shot. Running the AF in short bursts seems to give the AF algorithms a more precise feel for the features of the subject, so the AF doesn't run right across the range from zero to infinity. Assigning AF only to the AF button on the camera back can also sometimes help with the process of exercising more control over the AF and your shooting. Many people swear by the AF button. Just on the centre-focus point, since you have taken the time and effort to test for back and front focus, shot some focus charts etc, perhaps now you can also do some testing to identify the sensitivity boundaries around your centre-focus point... Setup a contrasty object (tennis ball? soccer ball? checkers board?), place it a working distance away against a neutral backdrop, and explore it with the camera AF in centre-point AF-S, monitoring the green hexagon to see when it lights up or not as you move across the focus target. UnknownVT did something like this with his K-x some time ago, using a simple pencil set up on a fence, and it was a good illustration of how precise even the K-x's centre-point could be. It's also worth rehashing the point that if you want to depend on the AF, and need to shoot wide-open all the time on lenses other than less than 50mm, the narrow DOF will oftentimes kill you as much as any AF sensor blunders.

07-03-2013, 02:00 PM	#17
Anvh Veteran Member Join Date: Sep 2011 Posts: 4,616	like RAWR says the AF button works very well, expecially with quickshift or HSM lenses. Je focus manually close to the subject and then turn on the AF for the last part. Almost 99% of the time it will lock onto the subject, since it's the sharpest and closest subject.