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| p.8 #9 · Canon autofocus information |
Which brings us to one of the earlier questions. Which method is best to focus. Center point and recompose, all point, or select the closest point manually to what we want in focus without recomposing.
If the center point is the most accurate with 2.8 lenses, looks like that would be preferred. But then you get into the angle error like was previously explained.
I and most other old guys have always been using FandRC since forever without a problem on film cameras--or, I should say, with manual focus cameras.
However, we rarely attempted to shoot as much razor-thin depth of field work as you youngsters these days. Whenever I did something like that, I was normally using a plain groundglass focusing screen, setting my composition first and focusing directly on the part of the subject that I wanted sharp--no FandRC. Obviously it was manual focusing.
I believe this issue has raised its head primarily because people are trying to do the same thing with autofocusing, but IMO if you're working with razor-thin depth of field and want the zone of sharpness to fall on a specific plane (like midway the forward eye--differences of only a few millimeters when body sway can be measured in two or three centimeters), you really need to be operating manually and not FandRC. Even body sway (yours or the subject's) is enough to throw off such narrow depth of field, so you'd have to watch closely to shoot at the moment it fell right where you wanted it.
This is a problem similar to that of a target pistol or rifle shooter firing "offhand" (without physical support). It's physically impossible for a human to remain absolutely still without support, so the shooter learns to watch the sights as his natural body sway moves the point of aim over the bullsey, then time his trigger squeeze to fire as the aimpoint is right over the bullseye.
In the same way, when shooting for a razor-thin depth of field, photographers will have to compose, focus manually, and then watch how the zone of focus moves as he and the subject sway natrually, timing the shutter release for when the zone of focus is precisely where the photographer wants it to be.