9 AF POINTS(eos 400D).... Which one produces the most sharpest picture?

[oliver]

Hi evryone! Im new here in this forum. Im a CANON EOS 400D user (my first camera given to me by my sister last Dec '07). Apart from the kit lens(18-55mm), I also purchased the cheap but amazing 50mm/1.8 II.  I wanted to appreciate & maximize my photographic potentials thats why I bought some photography books & attended some basic & not so advance photography sessions here in the Philippines. Slowly i have developed the keen sense in distinguishing the sharp & not so sharp shots. I spend 90% of my time shooting with the faster 50mm prime.
My question is simply about sharpness. I happened to experience this when I was shooting a head & shoulder portrait. I was shooting with my 50mm Handheld(f/2.2 @ 1/25 setting;vertical shooting mode;AF Mode; Manual Exposure Mode; Manual AF Point Selection Mode) using available light in our room, locking the focus in either eye(then recompose the shot) using the topmost AF point(vertical shooting) when I surprisingly noticed that there were times when the other eye of the subject was not that sharp as compared with the other. Why is that? Does this really happen with you guys? Or is it probaby because I can't make my hands steady with that 1/20 sec?
1. Is there really a significant sharpness difference in using the Manual or Automatic AF Point Selection Mode?
2. When using the Manual Selection, which AF Point seems to be the "sharpest"?
3. When using the Manual Selection, is the selected AF Point's performance affected by varying the aperture?

[Bob Atkins]

As long as the camera selects the focus point that you want, or you select it manually, there should be no significant difference msot of the time.

The center AF point should give slighly better accuracy on difficult subjects since it's a cross sensor and has a high precision mode when used with lenses f2.8 or faster.

I suspect you're simply seeing the effects of a shallow depth of field with a fast lens. You may also be moving the camera slighly after you have focused. Without IS, I would recommend a shutter speed of 1/80s or faster to avoid blur due to your hand shaking - or better still use a tripod! At 1/25s with a 50mm lens on a 400D, I'd expect quite a few shots to show motion blur.

[lukeap69]

Yup, that was I thought so too.

Be careful shooting at wide apertures due to shallow DOF. Happened to me lots of time.

BTW, I'm kabayan also (in Dubai).