Maximum Aperture - Canon EOS-3 Instructions Manual

● AF Sensitivity and the Lens' Maximum Aperture
The EOS-3's AF sensitivity in relation to the lens' maximum aperture is described
below.
The EOS-3's focusing points are all sensitive to horizontal lines. However, depending on
the maximum aperture of the lens, certain focusing points can also be sensitive to vertical
lines to enhance AF precision.
50
(1) With lenses whose maximum aperture is f/2.8 or
larger, the focusing points highlighted in the figure
become cross sensors sensitive to both vertical and
horizontal lines. The remaining 38 focusing points are
horizontal-line sensitive. Cross sensors (also used as
the center focusing point in the EOS-1 and EOS-1N)
attain higher AF performance and precision. The
sensor's vertical-line sensitivity is three times higher
than horizontal-line sensitivity.
(2) With the following lenses whose maximum aperture is
f/2.8 to f/4, high-precision AF is possible with the
center focusing point which works as a cross sensor.
The remaining 44 focusing points are horizontal-line
sensitive (except with EF 70-200mm f/2.8L USM +
Extender EF 1.4x).
28-80/2.8-4L, 300/4L, 300/4L IS, 500/4L IS,
600/4L, 600/4L IS, 70-200/4L
• With Extender EF 1.4x:
200/2.8L, 200/2.8L II, 300/2.8L, 300/2.8L IS,
400/2.8L, 400/2.8L II, 400/2.8L IS
• With Extender EF 2x:
135/2L, 200/1.8L
(3) With the following lenses, if the maximum aperture is
anywhere from f/6.7 to f/8 when an Extender is
attached, the center focusing point will be sensitive to
horizontal lines only. The other focusing points cannot
be used for AF.
• With Extender EF 1.4x:
400/5.6L, 500/4.5L, 100-400/4.5-5.6L IS
• With Extender EF 2x:
300/4L, 300/4L IS, 500/4L IS, 600/4L,
600/4L IS, 70-200/4L
• When the <
display shown on the right appears on
the LCD panel
> button is pressed, the