This is the twelfth article in a
series on "understanding your camera"
that I am writing as I teach camera basics and camera operation to my children.
Definitions
A 35mm film camera uses a film roll where each exposure is 36mm wide and 24mm high.
A full frame digital camera body mimics this exposure size, and has a digital sensor that is the same size
as the 35mm exposure.
This allows lenses designed for 35mm film cameras to be used on a full frame digital camera
and still provide the same
field of view as on a 35mm film camera.
A crop body is a digital camera which has a smaller sensor, which only "sees"
a portion of the field of view, making it look like you are closer to the subject being photographed.
That means for a given distance between the camera and the subject being photographed, a crop body
has a smaller
field of view
and a smaller angle of view than a full frame camera body.
full frame sensor vs smaller sensor and the impact on field of view (top view)
Impact of Sensor Size
The smaller sensor in a crop body has an impact on the
field of view,
with an apparent magnification of the
focal length.
This causes the effective focal length of a lens to be longer than the actual focal length,
ie, the effective focal length of a given lens on a crop body is longer than the same
lens is on a full frame body.
The minimum focus distance of a lens is not impacted by the size of a camera's sensor.
The
aperture
of a lens is not affected, but the
depth of field
for a given aperture is shallower on a full frame sensor than on a crop sensor.
This is because with equivalent fields of view, a crop camera has a shorter
distance to the subject than a full frame camera, and
the distance between camera and subject is one of the factors affecting
depth of field.
