Choosing a Metering Method

The 40D has four different schemes for evaluating the light received by its exposure sensors. You can choose among them by pressing the Metering Mode Selection button on the top panel, and using the Main Dial until the icon for the mode you want appears in the status LCD.

■ Evaluative. The 40D slices up the frame into 35 different zones, shown in Figure 4.3 (the status LCD icon is shown in the upper-left corner). The zones used are linked to the autofocus system. The camera evaluates the measurements, giving extra emphasis to the metering zones that indicate sharp focus, to make an educated guess about what kind of picture you're taking, based on examination of thousands of different real-world photos. For example, if the top sections of a picture are much lighter than the bottom portions, the algorithm can assume that the scene is a landscape photo with lots of sky. This mode is the best all-purpose metering method for most pictures. I'll explain how to choose an autofocus/exposure zone in the section on autofocus operation later in this chapter.

■ Partial. This is a faux Spot mode, using roughly nine percent of the image area to calculate exposure, which, as you can see in Figure 4.4, is a rather large spot. The status LCD icon is shown in the upper-left corner. One of the improvements brought by the introduction of the 40D's predecessor, the EOS 30D, was a true Spot mode, described later. Use this mode if the background is much brighter or darker than the subject.

■ Spot. This mode confines the reading to a limited area in the center of the viewfinder, as shown in Figure 4.5, making up only 3.8 percent of the image (slightly larger than the 3.5 percent Spot used in the 30D). This mode is useful when you want to base exposure on a small area in the frame. If that area is in the center of the frame, so much the better. If not, you'll have to make your meter reading and then lock exposure by pressing the shutter release halfway, or by pressing the AE-Lock button.

Figure 4.3

Evaluative metering uses 35 zones, linked to the autofocus points shown as red brackets.

C

(

)

3

L

IJJIJIJ J,U

i inn UJU

Partial metering uses a center spot that's roughly nine percent of the frame area.
Photo Appareil Ecran

Figure 4.5

Spot metering calculates exposure based on a center spot that's only 3.5 percent of the image area.

Figure 4.5

Spot metering calculates exposure based on a center spot that's only 3.5 percent of the image area.

■ Center-Weighted. In this mode, the exposure meter emphasizes a zone in the center of the frame to calculate exposure, as shown in Figure 4.6, on the theory that, for most pictures, the main subject will be located in the center. Center-weighting works best for portraits, architectural photos, and other pictures in which the most important subject is located in the middle of the frame. As the name suggests, the light reading is weighted towards the central portion, but information is also used from the rest of the frame. If your main subject is surrounded by very bright or very dark areas, the exposure might not be exactly right. However, this scheme works well in many situations if you don't want to use one of the other modes.

Figure 4.6

Center-Weighted metering calculates exposure based on the full frame, but emphasizes the center

Figure 4.6

Center-Weighted metering calculates exposure based on the full frame, but emphasizes the center

innn r r

IIJIJU JJJ

Was this article helpful?

0 0
Digital Cameras For Beginners

Digital Cameras For Beginners

Although we usually tend to think of the digital camera as the best thing since sliced bread, there are both pros and cons with its use. Nothing is available on the market that does not have both a good and a bad side, but the key is to weigh the good against the bad in order to come up with the best of both worlds.

Get My Free Ebook


Post a comment