Canon 80D Experience Manual page 26

Canon 80D Experience
capturing an image of a bird in a tree the camera has no idea you want the autofocus
system to zero in on the bird so that it is in sharp focus, and not the branches or leaves
near it or perhaps even some leaves closer to you and nowhere near the intended
subject.
The autofocus system of a dSLR plays a large role in allowing you to capture exactly
the shot you intend. In the Creative Zone Shooting Modes (P, Av, Tv, M, and Bulb-B)
you can, and should, take control of the autofocus system. The Viewfinder autofocus
system is comprised of the autofocus related controls, the autofocus AF Modes (also
called the AF Operation), the autofocus AF Area Selection Modes, the autofocus AF
Points, and the autofocus related menu and Custom Function items described at the
beginning of this text which customize how the AF system works. (Live View
autofocusing is slightly different, and will be covered later in this chapter.) You will select
an AF Mode typically based on if the subject is still (or perhaps only moving slightly or
relatively slowly), or if you wish to continuously track and retain focus on a moving
subject. And you will choose an AF Area Selection Mode based on how large of an area
you want the camera to look at to find or track your intended subject - in other words
how many AF Points will be active when attempting to focus on the subject. This can
range from a single AF Point to a wider Zone or Large Zone, to all the AF Points
available in the Viewfinder. You can set the AF Modes and AF Area Selection Modes in
a variety of combinations based on what and how you are shooting. Be sure to read the
Menu Settings and the Custom Functions Menus chapters first to make sure your
camera is properly set up to always display your active AF Point(s), and various other
recommended AF settings.
Viewfinder autofocus works by looking for contrast so you should try to focus (locate the
active AF Point as seen in the Viewfinder as in Figure 162) on a texture or a detail with
a pronounced line or some amount of contrast between light and dark. The camera may
not be able to focus on a large area of consistent color - such as an all-white wall or
clear blue sky, or even a uniformly colored and lit shirt - or on a subject that is too dark.
It can be disrupted by regular patterns or confused when looking through close objects
to objects farther away, such as looking through a fence. And it sometimes fails to work
well in dim light, though the center AF Point is more responsive than the outer AF Points
in low light situations (down to -3 EV for the center point). Also, the AF-Assist Beam
Firing of Custom Function C.Fn II-6 can assist in low light situations if you are using the
built-in flash or an optional Speedlite. All of the 45 AF Points are the accurate cross-type
points, so you should feel comfortable making use of any of them. (A cross-type AF
Point detects contrast in both the horizontal and vertical directions, as opposed to AF
Points which are only sensitive to contrast in one of these directions.) The center AF
Point of the 80D performs with additional sensitivity when using most Canon lenses with
an f/2.8 or wider maximum aperture. Note that with certain older Canon lenses, many of
the outer AF Points will not act as cross-type points. See pages 128-135 of the Canon
manual for this list of lenses.
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