35mm Equivalency EOS 500D/T1i
Saturday, December 26, 2009
35mm Equivalency
If you’re coming from a 35mm film camera background, then you might already
have certain ideas about focal length. For example, you probably think of a
50mm lens as a “normal” lens, that is, a lens with a field of view that’s roughly
equivalent to the human eye.
In turn, you probably think of anything longer than 50mm as being telephoto
and anything shorter as being wide-angle. To you, a 16mm lens is probably a
super-wide angle, while a 400mm is a long telephoto.
The image sensor in the Rebel T1i is smaller than a piece of 35mm film. All lenses
project a circular image onto the focal plane, and a rectangular crop is taken
from that to create the final image. But because its sensor is smaller, the T1i cuts
a smaller crop out of that circle.
In practical terms, this means that, for any given focal length, the field of view of a lens
on the canon eos 500D will be narrower than that same focal length on a 35mm camera.
To put it another way, on the Rebel T1i, a 50mm lens has the same field of view
as an 80mm lens on a 35mm film camera.
To calculate the 35mm equivalency of any lens you put on the T1i, simply multiply
the focal length of your lens by 1.6. So, if you have an 18–55 mm lens—a lens
that would be an ultrawide to normal lens on a 35mm film camera—you can
think of it as a 28.8 to 88mm lens in 35mm terms.
Another way of thinking about magnification is to pay attention to the field of
view. In the figure on the previous page, the center image has a much narrower
field of view than the left image. As focal length increases, the field of view captured—
that is, the distance from left to right—gets narrower.
On lenses, the “thickness,” or length of a lens, is measured in millimeters and is
referred to as the lens focal length. A longer focal length means a more telephoto
lens, which means more magnification and less field of view. So, a 300mm lens will
be more telephoto than an 80mm lens. We’ll be speaking about focal length a lot
in my coming article
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If you’re coming from a 35mm film camera background, then you might already
have certain ideas about focal length. For example, you probably think of a
50mm lens as a “normal” lens, that is, a lens with a field of view that’s roughly
equivalent to the human eye.
In turn, you probably think of anything longer than 50mm as being telephoto
and anything shorter as being wide-angle. To you, a 16mm lens is probably a
super-wide angle, while a 400mm is a long telephoto.
The image sensor in the Rebel T1i is smaller than a piece of 35mm film. All lenses
project a circular image onto the focal plane, and a rectangular crop is taken
from that to create the final image. But because its sensor is smaller, the T1i cuts
a smaller crop out of that circle.
In practical terms, this means that, for any given focal length, the field of view of a lens
on the canon eos 500D will be narrower than that same focal length on a 35mm camera.
To put it another way, on the Rebel T1i, a 50mm lens has the same field of view
as an 80mm lens on a 35mm film camera.
To calculate the 35mm equivalency of any lens you put on the T1i, simply multiply
the focal length of your lens by 1.6. So, if you have an 18–55 mm lens—a lens
that would be an ultrawide to normal lens on a 35mm film camera—you can
think of it as a 28.8 to 88mm lens in 35mm terms.
Another way of thinking about magnification is to pay attention to the field of
view. In the figure on the previous page, the center image has a much narrower
field of view than the left image. As focal length increases, the field of view captured—
that is, the distance from left to right—gets narrower.
On lenses, the “thickness,” or length of a lens, is measured in millimeters and is
referred to as the lens focal length. A longer focal length means a more telephoto
lens, which means more magnification and less field of view. So, a 300mm lens will
be more telephoto than an 80mm lens. We’ll be speaking about focal length a lot
in my coming article
[get this widget]
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