Get the Perfect Exposure -
Every Time!
By: TJ Tierney
 Did
you ever get back a fresh batch of film, only to be
disappointed in finding out that you got back
wash-out boring images.
The problem is that you didn’t expose your film
properly.
Whether we use a digital or film camera, we need to
be able to calculate exposure properly. But first,
we need to understand how the aperture and the
shutter work together. We also need to know how film
handles light, and the relationship between film
light sensitivity and f/stops.
Lets take a quick look at the main elements.
Aperture and f/stops: the aperture is an
opening in the centre of the lens through which
light passes. The amount of light which passes
through an aperture is indicated by f/stops. The
lower the f/stop the more light that passes through
the aperture. Opening up one full f/stop doubles the
amount of light entering the camera. F/4 admits
twice the light of f5.6.
Shutter: the shutter is a mechanical device
that controls the length of time that light is
allowed to act on the film. Each time you open the
shutter by one, we double the light, when we close
down the light by one we half the light. Opening the
shutter at 1 second allows twice the light as that
of a ½ second.
ISO (ASA): stands for International Standards
Organisation. The initials are used for film speed
which rates light sensitivity. A film with an ISO
number 100 is twice as light sensitive as a film
with an ISO of 50. The faster the film, the more
sensitive it is to light.
Most digital SLR have ISO settings built in to them.
If you are taking a low light image with a digital
camera use a slow ISO rating of 200 or upwards.
Getting the perfect exposure isn’t easy, but there
are several different ways of making it easier.
Using a light meter: there are two types of
light meters,
 1.
Reflected-light meter (the same that is built
into your camera) works by pointing the meter at
your subject.
2. Incident-light meter: instead of pointing
the meter at your subject, you stand beside the
subject and point the meter at the camera. The light
that falls on your subject will also fall on your
meter.
The most common way is to use the meter built into
your camera. All modern day cameras have a
reflected-light meter built in to them. But don’t
point the camera directly at your subject from 10
meters. This will more than likely underexpose your
image. Take the exposure reading up-close, then
return to the starting position and take your image.
It doesn’t matter which metering system we use, if
we don’t point them in the right direction our
images will return too dark or too bright. The key
is to know where to point the meter.
When I take a landscape image I normally take five
or six different readings. I take an incident-light
reading with my light meter to record the foreground
and a reflected-light reading of the sky.
If you are unsure take three or four images at
different exposure settings. Don’t let a perfect
picture moment pass by without recording it
flawlessly.
TJ Tierney. Award winning Irish Landscape
Photographer. If you are looking for more tips
visit:
Photo tips. To view some of his images visit his
on-line gallery:
Pictures of Ireland.
http://www.goldenirishlight.com/photographytips.html
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