What is camera metering and camera
Ever have problem with the photos that
the subjects look too dark and hardly recognizable? This is all about
the metering and exposure. In order to get a photo with good sharpness
and brightness, the exposure to the sensor needs to be correct.
Exposure is identified as the amount of light permitted into the sensor
(aperture setting) combines with the amount of time the light goes into
the sensor (shutter speed setting). It is also affected by the
sensitivity of the sensor (ISO setting).
In other words, in order for the exposure of a photo to be correct, the
aperture setting and the shutter speed setting must be correctly
Exposure is measured by EV (exposure value). EV is referred as 0 at the
setting of aperture = 1, shutter speed = 1s and ISO = 100. For each
stop drop in either section, the EV will increase by 1. For example, if
aperture is drop one stop from 1 to 1/1.4, shutter speed remains as 1s
and ISO remain as 100, then the EV value is 1. If, the aperture is
1/1.4, the shutter speed drops one stop from 1s to 1/2s and ISO remain
as 100, the EV will become 2.
The higher the Exposure Value simply means the photo is over-expose and
we need to set to higher shutter speed, smaller aperture and low
sensitivity. On the other hand, if the exposure value is negative, then
the photo is under-expose and we will need to set bigger aperture,
slower shutter speed and higher sensitivity accordingly.
As shown here, the exposure differences in each stop in aperture
setting is actually same as the exposure differences in each stop in
shutter speed setting.
For example, if aperture setting drops one stop from f 1/5.6 to f 1/8,
the difference of exposure is actually same as shutter speed setting
drops one stop from 1/30s to 1/60s. EV increase by 1 whenever the
aperture drop one stop and the other setting remain, EV also increase
by 1 whenever shutter speed drop one stop while other setting remain.
The difference of exposure is the same.
By understanding how exposure works, we get to know how to change the
shutter speed, aperture and sensitivity setting depending on various
For example, in a certain portraits photo shoot, the exposure metered
shows that the aperture needs to be at F8 and shutter speed at 1/125s.
However base on the EV, we can change the aperture three stop higher to
F2.8 and subsequently change the shutter speed setting three stop lower
to 1/1000s. The exposure of this particular photo will be the same;
however we get to use a bigger aperture setting.
Metering is how the camera detects the amount of light on the subject
and determines the number of EV needed for a proper exposure.
There are a few types of metering mode available in DSLR nowadays
Matrix metering - Different types of
cameras have different types of matrix metering. Each having different
algorithm and zones of metering and the system will decide on the
suitable EV for correct exposure.
Center weighted metering - This metering
mode will emphasize on the exposure at the center of the photos.
Spot metering - This mode meters at the
center spot/certain spot of the camera. The small area of metering is
generally just 3~5% of the frame.
With better understanding of Exposure
Value and how it works, we get to control the parts of the photo that
we wish to emphasize on and need it to be clearly exposed. For example,
in portraits photo, you should meter on the face of the person with
either center weighted metering mode. For an even better result, you
can even do spot metering on the eye of the person. This is to ensure
that the exposure is set or metered to the brightness on the person.
With proper metering, the subject will looks clear and sharp in the
This explains on how to use spot metering. First, aim the spot metering
point directly at the eye of the subject. Press and hold the metering
button while changing the composition of the photos. Then, press the