"P" (programmed auto) mode is ideal for parties, festivals, and other occasions when you don't have time to make settings one at a time.
"S" (shutter-priority auto) mode is great for motor sports and other fast action scenes.
"A" (aperture-priority auto) mode offers most control of depth of field.

Since we described in the 4th and 5th issue how the Matrix Metering System is reliable for virtually any lighting situation, including backlit scenes, let's discuss in this issue our last point regarding exposure -- the exposure compensation.

Why Compensation is necessary
The metering system in most single-lens reflex (SLR) cameras measures light reflected off the subject. As mentioned in the last issue, light passing through the lens is measured inside the camera in the TTL system. This system, together with the Matrix Metering System, can be used to set optimal exposure for virtually every situation.

The internal metering system, however, is designed to provide optimal exposure for an 18% reflectivity subject (the so-called "standard gray card"). When subject reflectivity is considerably different, as with subjects surrounded by snow or backlighting, exposure setting function of automatic cameras may not work properly. In such cases, exposure compensation technique can help solve the problem.

The following tables show typical situations for exposure conpensation.

When subject has many bright areas (more than 18% reflectivity)
Without compensation	+1 EV compensation

When subject has many dark areas (less than 18% reflectivity)
Without compensation	-1 EV compensation

Reflectivity of a main subject

                        Over 18%: Under-exposure --> Plus (+)
                   •--- compensation (Images of snow, close-ups of
                   |    white or yellow subjects, backlighting, etc.)
                   | 
Reflectivity       |
     of        ----•--- 18%: Optimum exposure 
a main subject     |
                   |
                   |    Under 18%: Over-exposure --> Minus (-)
                   •--- compensation (Images of deep green, shadow,
                        dark images, etc.)

Amount of exposure compensation
Exposure compensation in SLR cameras is generally made by rotating a dial or pressing a button. Because the amount of compensation should vary according to situation, experience is essential to get precisely the exposure desired.

Exposure compensation guidelines

• Scene with sun: 0 to +3 EV
• Snow or shining water: +2/3 to 3 EV
• Close-up of white or yellow flower: +1/3 to +1-2/3 EV
• Dim night sky: 0 to +2 EV
• Twilight landscape:-2/3 to 0 EV
• Steam locomotive (black subject): -1-1/3 to -2/3 EV

Note: When exposure compensation is made on a Nikon SLR, the numerical compensation value is displayed on the top LCD and/or in the viewfinder. The displayed values and compensation correspond as shown below.

Try exposure bracketing
As described above, even when you know in which direction (+ or -) to compensate for exposure, you may not know how much to compensate. The delicate lighting of sunrises and sunsets is especially difficult to judge. In such cases, try taking a number of shots, each with a slightly different exposure. This is called "exposure bracketing". Remember, you may only get one chance to capture your shot, so shooting a number of pictures of an important scene helps to ensure that you get exactly the right shot you're looking for.

-1 EV compensation	Without compensation	+1 EV compensation

Use the Auto Exposure Bracketing
By simply setting the bracketing step and number of shots, the camera will shoot the number of shots that you specify, and offset the exposure by the specified EV steps. This Auto Exposure Bracketing function is built into some Nikon AF cameras, or can be used otherwise by attaching an optional multi-control back featuring the function.