Canon EOS-1D Mark II Digial Советы и техника - Страница 11

Autofocusing Techniques:

Off-Center Focusing Points vs.

"Focus Lock and

Recompose"

Fine-Tuning Your Camera

with Custom and

Personal Functions

Some might think that it's a good idea to keep the shutter button half-pressed all the

time, but battery life will be shortened significantly by that technique. The best balance

between power consumption and AF performance is to anticipate picture-taking

opportunities and do not press the shutter button halfway until just a second or two

before pressing all the way for the shot.

The 45-point Area AF sensor covers a significant portion of the picture area, especially

with the original EOS-1D and EOS-1D Mark II. However, many photographers never use

the off-center focusing points, preferring the old-fashioned method of locking focus with

the center point and then recomposing for the actual image. Before multi-point AF

cameras were available, "Focus Lock and Recompose" (FLR) or manual focus were the

only choices available. That's no longer the case.

FLR is sufficiently accurate for photographing distant subjects, but it can cause focusing

errors, especially backfocus, when photographing subjects within about 15 feet of the

camera. This is often the case during portraiture. For optimum focusing performance

with close subjects, we recommend avoiding the FLR technique. Instead, use an off-

center focusing point or focus manually.

EOS-1 class digital SLRs are equipped with an extensive variety of Custom Functions

(C.Fn) and Personal Functions (P.Fn) that allow photographers to tailor many aspects of

camera operation according to personal preferences. Although there are minor

differences in the quantity and variety of C.Fns and P.Fns according to individual camera

models, most of them are consistent across the product line. For the purposes of this

document, we will concentrate on C.Fns and P.Fns that affect AF performance with EOS-1

class digital SLRs.

Custom Function 4 allows the photographer to control which button on the camera is

used to start or stop AF. It also ties in with AE Lock when the camera is set to an AE

mode.

• C.Fn 4-0 (the default setting) starts AF and AE when the shutter button is pressed

halfway. AE Locks automatically upon focus completion when the camera is set for the

combination of One-Shot AF and Evaluative Metering. With other AF modes or metering

patterns, AE Lock can be initiated manually by pressing the AE Lock button on the

back of the camera.

• C.Fn 4-1 switches AF start to the AE Lock button, and starts AE Lock in AE modes with

any metering pattern when the shutter button is pressed halfway. This mode is

popular with sports photographers and some photojournalists, especially those who

originally learned photography with manual focus SLRs. It works particularly well with

USM lenses that have distance scales, because such lenses feature full-time manual

focusing even when the lens is set for AF. With C.Fn 4-1, the photographer can

manually focus such a lens at any time, and then start or stop AF independently from

I. CAMERA FEATURES AND OPERATION