Cameras
come with two types of zooms: optical and digital.
Optical
zoom is the zooming capacity [=the capacity to enlarge] of the lens. This is
the real zoom. It is achieved by a lens combination. Expensive cameras mostly
have lenses with high zoom range. Still more expensive cameras have one regular
lens and a number of zoom lenses that can be fitted in place of the regular
lens. The bulky cameras with very long hood as seen with sports and wildlife photographers
have lenses with zooms of even 2000 times. However, the size and depth of the pocket
camera poses a severe limitation on optical zoom. In most pocket cameras, zooms
of 2 to 30-40 times are available.
For normal
cameras used for general day-to-day photography and amateur travel photography,
a zoom of around 3-4 times is good enough. In most cases, you end up using the
camera without zoom.
Zoom should
not be used without applying mind. When you use zoom, the lenses adjust themselves
in a manner that a smaller portion of the scene is captured and is blown into a
bigger size than normal. This leads to some distortion in the apparent distance
between the distant and near objects [called ‘depth of field, to be discussed separately].
It also reduces the focus of the picture beyond the main object.
Why is
digital zoom not useful?
Digital
zoom is nothing but artificial shortening of image taken by the camera sensor
and then expanding it to a higher size. It is like cutting the sides of a photo
print of 10” x 8” by 2” and then stretching the 8” x 6” photo back to 10” x 8”.
So, this zoom spoils the photo rather than adding anything to it.
So don’t
get fooled by ‘4x digital zoom ‘ or ‘12x total zoom’. In calculating this ‘total
zoom’, manufacturers and sellers multiply the optical and digital zoom
capacities of the camera.
Cellphone-cameras
usually have digital zoom only. These cameras already suffer from a poor
quality lens and other aspects; applying digital zoom tends to further spoil
the quality of photos taken with such cameras.
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