This is the
question I get asked most frequently about photography.
"What is exposure and how do I know which camera
settings to use".
The first question is
pretty easy to answer but the second part is a little
more difficult. The reason for this is because the
answer is subjective. The settings you choose will have
an effect on how the photograph will look in many
different ways. I will attempt to answer both questions
as effectively as I can. While parts of my answer may
not be technically perfect, I think you will get the
Photographic exposure is
the build up or recording of an image on a
photosensitive (light sensitive) material or device by
controlling the amount of light that the material or
device is exposed or open to. 'Material' usually meaning
photographic film and 'device' in this case meaning a
digital cameras sensor. I hope that makes sense to you.
It's important to realize
that there are basically 3 controls to exposure. Two of
them are camera settings but the third is the
sensitivity of the recording media, whether it's
photographic film or a digital camera sensor. This
sensitivity is expressed as a numerical value usually
with an "ASA" or "ISO" preceding the number.
The numerical value used
to express the sensitivity of photographic film or a
digital sensor increases with the media's
photosensitivity. As an example, ASA or ISO 100 is
exactly half as sensitive to light as 200, 200 is half
as sensitive as 400 and so on. Therefore it would take
less light to create a good exposure on ASA 200 then it
would to create a good exposure on ASA 100. I like to
compare photographic exposure to filling a water bucket
in my explanation. Lets just say that film was a light
bucket. It would take twice as much light to fill an ASA
100 bucket as it would and ASA 200 bucket. Just remember
that the higher the number the more sensitive the media.