Lens research
Lenses come
in all shapes and sizes and many are designed for specific purposes, however
the first thing to grasp is how the size of your camera’s sensor will affect
its stated focal length. Before digital cameras, 35mm film SLRs all used the
same 24 x 36mm film stock. A standard 50mm prime therefore produced the same
field of view regardless of the camera it was mounted to.
In the
digital age, however, sensors come in a number of different sizes, which in
turn affects the effective focal length of the lens. This is because sensors
that are smaller than 35mm only capture a middle portion of the image generated
by a lens. They effectively crop out the sides and magnify the middle. This has
the effect of increasing the stated focal length of any given lens. The extent
to which each type of sensor does this is usually referred to as its ‘crop
factor’.
Macro Lens
Macros lenses are used to
capture up close pictures of things and show more details. The lens with pick
these details up because; limited depth of
field is an important consideration in macro photography. Depth of
field is really small when focusing on close objects. A small aperture
is often required to produce really sharp images of a 3D subject. This means a
slow shutter speed is required, good lighting, or a high ISO.
35 mm equivalent
magnification, or 35 mm equivalent reproduction ratio, is a measure that
indicates the apparent magnification achieved with a small sensor format, or
"crop sensor" digital camera compared to a 35 mm-based image
enlarged to the same print size. The term is useful because many photographers
are familiar with the 35 mm film format.
To calculate
35 mm equivalent reproduction ratio, multiply the maximum magnification of
the lens by the 35 mm conversion factor, or "crop factor" of the
camera. If you took a photograph of a mm ruler placed vertically in the frame
focused at the maximum magnification distance of the lens and measure the
height of the frame. 
No comments:
Post a Comment