Article
Exposure
To take a photograph we take an exposure,
this means we allow a controlled amount of light onto a sensitive surface.
In the old days it was glass plates, then film, now digital sensors. The same
concepts of exposure apply to each and to movie film and video, which is
only a series of still images recorded.
There are 6 components to the exposure:-
-
the amount of light
-
the sensitivity of the recording device,
film, sensor ....
-
the length of time the shutter is open
(shutter speed)
-
the size of the hole the light
passes through
-
the focal length of the lens
-
the distance from the hole to the
recording medium
The last two are often overlooked, and you
may like to think of there being the same amount of light but it being
spread out thinner over a larger area, or concentrated onto a smaller area.
We combine the last three of these together as the
Aperture,
represented by its own system of F numbers.
So we have reduced this to 4 controllable
variables in routine use.
We can vary any of these so as to get
the results we require.
We can vary the light by
-
increasing the amount of light by
time of day, weather conditions etc
-
using
Reflectors
-
providing artificial light, in the form of constant light such as
Cool-Lite's
or bursts of light with
Flash
-
reduce
it using diffusers, putting
something between the light source and subject to reduce the amount
of light falling on the subject
-
reduce the light able to enter the
lens by using
filters,
overall with Neutral
Density filters
or over a part of the scene with
Graduated Neutral Density filters (grads).
Change the sensitivity of the
recording
-
with digital or video, changing
the ISO setting
-
with film (still or movie)
putting in a faster or slower film (ASA or ISO)
Changing the shutter speed
-
higher speeds to stop action,
and cope with camera shake
-
slower speeds to create blur,
moving water effects
and
the like
-
very slow speeds to record
star trails, to take images that moving items are not shown in.
Changing the aperture
-
Smaller hole large F number i.e. f22 has a greater
Depth of Field
(DOF)
-
larger hole with smaller
F
number i.e. f2 for a reduced depth of field, for example
throwing the background out of focus
To get a fuller understanding
of exposure please follow the Exposure Article Route (see
below).
<<
^
Exposure
Article Route
^
>>
Exposure
required and Sunny 16 Rule
See below for details
Exposure
Article Route
The Exposure Article
Route
takes you through a series of articles relating to exposure and
the components of it. Clicking on the
<<
or
>>
will take you back or forward, the next forward link is also
shown. Clicking on either of the
^
symbols will return you to this page.
The route is:-
-
Exposure
-
Exposure
required and Sunny 16 Rule
-
Exposure with an
Exposure Meter
-
Zone
Systems Photography
-
EV and the EV
Table
-
Aperture
-
Shutter
Speed
-
ISO and ASA
-
Comparative Table of ISO, ASA , DIN and GOST
See also
Exposure
required and sunny 16 rule
Exposure with an
exposure meter
EV table
Zone systems photography
Aperture
Shutter speed
ISO and ASA
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