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01-16-2011, 01:06 AM   #16
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QuoteOriginally posted by Canada_Rockies Quote
The biggest problem with AF and birds is that the AF will focus on the branch behind the bird rather than the bird. The human eye works much better than the mechanicals. For birds in flight (BIF) auto focus will work, but otherwise manual focus is best. I bought a Sigma 170-500 AF lens some years back, and sold it. I got way more keepers with the manual lens when the bird was in the bushes.

I also did not mention in my reply above that I have a focus magnifier on the camera, the Pentax 1.3X. It helps some, but not as much as the coarser screen. Both together are a nice touch. It took a while to get used to having to move my eye to read the data display at the bottom of the screen with the magnifier.
change the AF mode? they have several mode and you can choose spot or simply just one of the focus point... stick it right at the bird and it should work... I've never done bird watching, I've had more problem when it's closer than the minimum distance of the lens, i rare have problem when it's far enough (well sometimes it seeks too much since there's not enough contrast, but if you get used to it, there's some small things to do and get it to focus on the right spot).

01-16-2011, 11:00 AM   #17
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QuoteOriginally posted by clockwork247 Quote
change the AF mode? they have several mode and you can choose spot or simply just one of the focus point... stick it right at the bird and it should work... I've never done bird watching, I've had more problem when it's closer than the minimum distance of the lens, i rare have problem when it's far enough (well sometimes it seeks too much since there's not enough contrast, but if you get used to it, there's some small things to do and get it to focus on the right spot).
I'm afraid that the focus area is too large to be accurate for BIB (Birds in Bushes). Don't rely on the size of the little red square, it defines only which of the focus areas is in use and is in no way indicative of how large the focus area is. The focus system relies upon high contrast edges, and bird feathers don't have those edges. If any hard edge intrudes into the focus area, the camera will use that rather than the bird. My eye can tell me that the bird is in focus, and ignore any twigs or branches that are in front of the bird or close to the side of the bird and behind it. An AF lens cannot do that. If you want to try it, you can get a pretty good idea of how large a focus point is by creating a target that is a large blank area with a single high contrast element and focusing set to the central area. See just how far off center the contrast element can be and still cause the camera to gain focus on it. You might be surprised. With the standard screen, the central focus area on my K10D is about the size of the ( ) screen area.
01-16-2011, 10:19 PM   #18
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QuoteOriginally posted by Canada_Rockies Quote
I'm afraid that the focus area is too large to be accurate for BIB (Birds in Bushes). Don't rely on the size of the little red square, it defines only which of the focus areas is in use and is in no way indicative of how large the focus area is. The focus system relies upon high contrast edges, and bird feathers don't have those edges. If any hard edge intrudes into the focus area, the camera will use that rather than the bird. My eye can tell me that the bird is in focus, and ignore any twigs or branches that are in front of the bird or close to the side of the bird and behind it. An AF lens cannot do that. If you want to try it, you can get a pretty good idea of how large a focus point is by creating a target that is a large blank area with a single high contrast element and focusing set to the central area. See just how far off center the contrast element can be and still cause the camera to gain focus on it. You might be surprised. With the standard screen, the central focus area on my K10D is about the size of the ( ) screen area.
hmm, that's interesting, i've never done bird watching so I'm pretty clueless on that, but it does make sense, i take pictures of flower and sometimes I get focus problem because there's not enough contrast for the camera to pick up (alot of flowers are 1 color lol)... in that case, manual focus is probably the best way out... but I'm pretty bad at it, alot of times I think something is focus (manual focus), but there's no light indicator (meaning the camera says it's not haha)... I'd have to say that to me there's no "exact" focus, I can move the focus ring slightly and still look the same to me (which means it's more of a range VS an exact specific distance)...
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