Page 70 - (DK) Advanced Photography Guide

68 EXPLAINING | METERING

EXPOSURE METERING AVERAGE

REFLECTIVITY
To know what aperture, shutter, and ISO values to set, you The term “average reflectivity” is
need to use an exposure meter, which measures the brightness used for a scene that reflects 18%
levels of light. After this simple step, you interpret the reading in of the light that falls on it. Averagely
reflective colors are known
order to produce accurate, consistent exposures. First, though, as midtones and include
it is important to know how an exposure meter works and mid-grays and other
colors of a similar
what its limitations are, since this will give you full control level of brightness. 18% GRAY
over exposure, and you will be better informed about
how to fix any problems that might arise.

Incident versus
reflective metering
There are two ways to meter a scene.
You can measure the amount of light
falling on it or the amount of light
that is reflected from it. A handheld
light meter takes an incident reading,
and camera meters take a reflective
reading. Incident metering is generally
more accurate, because reflected
metering assumes that a scene
has average reflectivity. Darker ▲ Handheld meter readings are taken ▲ The meter built into a camera takes
or lighter scenes will be over- or close to the subject. This makes them a reflective reading. It is a useful tool,
underexposed respectively. less convenient than a camera meter, but it can be fooled by subjects that
if your subject is far away.
are not 18% reflective.
GRAY CARD

A gray card (or 18% gray card) is
calibrated to reflect 18% of the light
that falls on it, making it averagely
reflective (see top right). Use it to help
choose the correct camera settings
for your shot, especially if your scene
has a higher- or lower-than-average
reflectivity that could cause an error
in exposure. Take a meter reading
from the card, and use this to POSITION THE GRAY CARD TAKE THE READING
determine your exposure, rather Set the exposure mode to Manual Take a meter reading, ensuring
than a reading from the scene and the metering mode to Spot. Place that the gray card fills the spot-metering
you are shooting. the 18% gray card close to your subject, area. Set the required shutter speed and
and point your camera at it. aperture, then remove the card.

US_068-069_Understand_ExposureMetering.indd 68 07/02/2018 14:47