Canon T 70 - Manual (Page 82)

(1) Exposure
Taking a picture is a mailer of controlling me
amount kght allcv/ed to fall on the film This is
called exposure. When ycu press the shutter
button some blades insiOe Iho lens, ceiled a dt-
aphragrr. close dcvm to form an opening, colled
the aperture
Almost simuitareojsly. the first shutter curtain
starts to move inside the camera. A second shut­
ter curtain follows ft after a fixed inter*/ai which
you can control on the display ponei. The
amount of ighl mat exposes a frame depends
on the shutter speed and me size of Iho aperture
Fcr the same exposure, a chartge in me shutter
speed requires an ocuai and opposite cnange
the aperture. When in the shutter*priorit^* AE
mede, me T70 outomatica^ty imakes this change
in aperture when you change the shutter speed.
In programmec AE. the camera aulcmaticaily
chooses a combination of shutter speed and
aperture ter correct ex^sure. Thero oro usuairy
several ccmbralicns of shutter speed and aper*
ture v^hich
w\\ give the samo exf^sure and this
is the koy to crodtrve photography.