Originally posted by Hayashi My understanding is that, if I want to shoot an object not moving or moving very very slowly, AFS can be much better option than AFC.
AFC calculates the distance to the subject under the active AF point multiple times per second.
The measuring takes place under the AF point (exactly there) and it is based upon comparing lines of pixels.
So in AFC you as user can force the camera to miss the correct focus in two ways:
a) your aim at the subject is not perfect and the
AF point wanders/swings over the subject. If your swinging around of the AF point ever let it wander to an situation where the distance to what lies behind the AF point is not your desired focus plane you dont get the desired results. Here let us assume you briefly point the AF point at something beside or behind the insect. The AF works absolutely correctly if it then focusses beside or behind the insect.
Keep in mind the measuring is done by comparing pixels. So even swaying 2 millimeters can have an impact.
b) your
setting of allowed AF points lets the camera make some decisions automatically (area AF or similar). Chances are that the camera believes it shall use an AF point over a part of the frame that is not what you would want it to. If you really want to aim at a static insect which is small in the frame, selecting a single AF point yourself avoids this.
For the static insect scenario AFS + personally selected single AF point is the best way to go.
AFC is not always a bad choice for static subjects. For example shooting a human face portrait can work well with AFC + auto area (due to eye recognition).
People want AF to work for millions of scenarios and this does absolutely require the users today to make a list of specific settings ideal to a specific scenario.
So no, there can not be a single "best" setting for "wildlife". A sitting insect, a jumping horse and flying bird - they all require different settings. And ten different other scenarios probably need ten different settings.