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Multiple questions about AF points

iunlock

New Iberia, US
47 posts

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iunlock Silver Member Nikonian since 27th Jan 2012
Fri 20-Sep-13 04:20 PM

I have had my new D800 for a week now and I am just now getting around to shooting it and checking the auto focus for sharpness. I have Darrell Young's book; Mastering the Nikon D800. I have been reading page 457 over & over again about cross type AF sensors. And I have some questions about this.

1. When Darrell discusses the maximum aperture of the lens, I am assuming that he is meaning the lens "SET" maximum aperture, and that this is not referring to what aperture I am shooting at, am I correct?

2. The lens that I have been shooting with is a 70-200 f2.8 VRII, this means that I should have 15 cross type AF sensors in the center of my view finder. I have tested the camera to see if my copy has the left focus problem, it does not. I have shot against a brick wall using center left and right AF sensors and all are nice and sharp. However, when I am taking pictures of my dog as he walks around the yard, I am noticing a small amount of difference in sharpness from the extreme far right and left AF sensors compared to the center AF sensors. The right and left sensors would not be cross type, while the center one is. The center sensor is very sharp, while the outside left and right are not as sharp.
Is this normal? should I see any difference in sharpness between the two types of sensors?
If this is the case, when do you guys use the outside, non-cross type sensors?

3. I would assume that for a portrait, we would turn the camera vertically and place the far right AF sensor, (which when the camera is vertical would be the top AF sensor,) on the model's eye. However, since this is not a cross type sensor would this be the best focussing technique for a portrait? or should I use one of the center cross type sensors to focus on the model's eye, and recompose the image before releasing the shutter?

Im sorry that this is so long. I'm just trying to get a handle on my focussing.
Thanks for any help.

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