主题：【求助】新手入道，请高人指导购机 -- Sulfur

“30D,5D的F2.8模块只有1个方向.”

下面是5D说明书上的原话：

Lens’ Maximum Aperture and AF Sensitivity

The EOS 5D will execute high-precision AF with lenses whose maximum aperture is f/2.8 or larger.

With lenses whose maximum aperture is f/2.8 or larger*

With the center AF point, high-precision, cross-type AF sensitive to both vertical and horizontal lines is possible. With cross-type AF, vertical-line detection is twice as sensitive as horizontal-line detection. The other eight AF points are horizontal-line sensitive or vertical-line sensitive.

* Except with the EF28-80mm f/2.8-4L USM and EF50mm f/2.5 Compact Macro lenses.

With lenses whose maximum aperture is larger than f/5.6

The center AF point is a cross-type AF sensor. The other eight AF

points are horizontal-line sensitive or vertical-line sensitive.

The spot metering circle has six invisible Assist AF points (see left illustration) that function in the AI SERVO AF mode. The Assist AF points have the same vertical-line sensitivity as the center AF point at f/2.8, and the Assist AF points have horizontal-line sensitivity at f/5.6.

俺把火环和中心对焦大概搞混了，不过看起来中心是有两个方向的哈。