The format
of the camera us use has certain proportions - 2:3 in the case of 35mm.
This is a proportion based on two simple numbers and the frame can then
be sub-divided according to this ratio.

Renaissance
artists decided that these ratios produced a static division in the
image and by contrast more dynamic divisions could be created with more
interesting ratios. he olden section, which was know to the Greeks is
the best known "harmonious" division. Based on pure geometry
and the elegance of the division lies in the fact that all the areas
are integrally related. The ratio of the small section to the larger
one is the same as the larger section to the entire frame. Sub-division
of the 35mm frame according to the golden section is very close to the
frame itself - 2:3.

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While a painter
might deliberately divide the frame in this way photographers tend to
work in a much more intuitive manner. However making yourself aware
of the proportions of these divisions allows you to apply them in an
approximate way when framing the subject.

The golden
section is not the only method of creating harmonious divisions and
if you are interested you can find info on this.

Most photographs
are taken with a format equivalent to 35mm film

While it
has a balanced proportion it is also quite familiar and predictable.
Other film formats include.

Film formats

Each of these has
is own size or area and the larger the area generally the more
quality or more information the negative contains.

However, in our consideration
for design we need to consider the ratio of one side to the
other.

With 4.5 X 6 cm 120
roll film, the ratio is the same as 4x5" and 8x10"
sheet film. Often this is refereed to as the ideal format.