Learning Objective 1
Research on
Lenses.
1.1 Evaluate the
potential for creating images.
Fisheye Lens.
A fisheye lens is an ultra wide-angle lens that produces strong visual distortion
intended to create a wide panoramic or hemispherical image. Fisheye lenses achieve extremely
wide angles of view by forgoing producing images with straight
lines of perspective, opting instead for a special mapping, which gives images
a characteristic convex non-rectilinear appearance. The term fisheye was coined in 1906 by American
physicist and inventor Robert W. Wood based on how a fish would see an
ultra-wide hemispherical view from beneath the water (a phenomenon known as Snell's window). Their first practical use was in the 1920s for use in meteorology to study cloud formation giving them the name
"whole-sky lenses". The angle of view of a fisheye lens is usually
between 100 and 180 degrees while
the focal lengths depend on the film format they are designed for. Mass-produced fisheye lenses for photography first appeared in the early 1960s and are generally used for their
unique, distorted appearance. For the popular 35 mm film format, typical focal lengths of fisheye
lenses are between 8 mm and 10 mm for circular images, and
15–16 mm for full-frame images. For digital cameras using smaller
electronic imagers such as 1/4" and 1/3" format CCD or CMOS sensors,
the focal length of "miniature" fisheye lenses can be as short as 1
to 2mm.
Macro Lens.
Macro
photography is extreme close-up photography, usually of very small subjects, in which the size of the subject in
the photograph is greater than life size. By
some definition ns, a macro photograph is
one in which the size of the subject on the negative or image sensor is life size or greater. However in other uses it refers to a
finished photograph of a subject at greater than life size. The ratio of the
subject size on the film plane (or sensor plane) to the actual subject size is
known as the reproduction ratio. Likewise, a macro lens is
classically a lens capable of reproduction ratios greater than 1:1, although it
often refers to any lens with a large reproduction ratio, despite rarely
exceeding 1:1. "Macro"
lenses specifically designed for close-up work, with a long barrel for close
focusing and optimized for high reproduction ratios, are one of the most common
tools for macro photography. (Unlike most other lens makers, Nikon designates
its macro lenses as "Micro" because of their original use in
making microform.) Most modern macro lenses can focus
continuously to infinity as well and can provide excellent optical quality for
normal photography. True macro lenses, such as the Canon MP-E
65 mm f/2.8 or
Minolta AF 3x-1x 1.7-2.8 Macro, can achieve higher magnification than life
size, enabling photography of the structure of small insect eyes, snowflakes,
and other minuscule objects. Others, such as the Infinity Photo-Optical's
TS-160 can achieve magnifications from 0-18x on sensor, focusing from infinity
down to 18 mm from the object.
Macro lenses of different focal lengths find
different uses:
Continuously-variable focal length –
suitable for virtually all macro subjects.
45–65 mm – product photography,
small objects that can be approached closely without causing undesirable
influence, and scenes requiring natural background perspective.
90–105 mm – insects, flowers, and
small objects from a comfortable distance.
150–200 mm – insects and other
small animals where additional working distance is required.
Telephoto lens.
In photography and cinematography, a telephoto lens is
a specific type of a long-focus lens in
which the physical length of the lens is shorter than the focal length. This is achieved by incorporating
a special lens group known as a telephoto group that
extends the light path to create a long-focus lens in a much shorter overall design. The angle of view and other effects of long-focus lenses are the same for telephoto lenses of the
same specified focal length. Long-focal-length lenses are often informally
referred to as telephoto lenses although this is technically
incorrect: a telephoto lens specifically incorporates the telephoto group.
Telephoto lenses are sometimes broken into the further sub-types of medium telephoto: lenses covering between a 30° and 10° field of
view (85mm to 135mm in 35mm film format), and super telephoto: lenses covering
between 8° through less than 1° field of view (over 300mm in 35mm film format).
In contrast to a telephoto lens, for any given
focal length a simple lens of non-telephoto design is constructed from one lens (which can, to minimize aberrations, consist of several
elements to form an
achromatic). To focus on an object at infinity,
the distance from this single lens to focal plane of the camera (where the
sensor or film is respectively) has to be adjusted to this focal length. For
example given a focal length of 500 mm, the distance between lens and
focal plane is 500 mm. The farther the focal length is increased, the more
the physical length of such a simple lens makes it unwieldy.
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