Quote:
Originally Posted by 49erbruin
I've been wrestling with this too. My main subject is my ~1 1/2 year old daughter who, of course, doesn't stay still for long. I was shooting her at ~f/2.5 with my 50 mm 1.4, but the photos weren't as sharp as I felt they should be with that lens.
A photographer friend suggested I 1) Try practicing at least at f/4 for a bit, since I'm not a super-experienced photographer; 2) DON'T use the center focus point and use switch to the correct point instead and 3) move my auto focus to AI Servo on my Canon XTi to help to better track my toddler.
I tried this yesterday and got MUCH sharper shots and good bokeh too! Hope that helps...
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Wrong-it is better to only use the centre focus point; here's why:
In your camera’s viewfinder, depending on camera-flagship models generally have many focusing spots, and lesser, entry-level dslr’s will have around 5 focusing spots. With lens wide open, any of these spots can be used for selecting where to auto focus-But, depending on maximum aperture of lens in use, the ones you are able to use get fewer. Top-of-the-line cameras will only have the centre spot usable at F8,and entry level cameras at F5.6, and less than that, even these single spots aren’t reliable.]
Actually it is more beneficial to set auto focus by the centre spot, then re-compose, rather than use the peripheral spots-The reason being that only the centre spot has vertical and horizontal pixel rows. This means that if you use the peripheral spots (top and bottom spots have horizontal pixels only and right and left spots have vertical pixels only) To focus, you must have a part of the scene crossing a line of pixels at 90 degrees, and the centre spot gives you a more accurate reading ,having both vertical and horizontal pixels)