Lens hood
Encyclopedia
In photography
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...

, a lens hood or lens shade is a device used on the end of a lens
Photographic lens
A camera lens is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.While in principle a simple convex lens will suffice, in...

 to block the sun or other light source in order to prevent glare
Glare (vision)
Glare is difficulty seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. Because of this, some cars include mirrors with automatic anti-glare functions....

 and lens flare
Lens flare
Lens flare is the light scattered in lens systems through generally unwanted image formation mechanisms, such as internal reflection and scattering from material inhomogeneities in the lens. These mechanisms differ from the intended image formation mechanism that depends on refraction of the image...

.

The geometry of the lens hood can vary from a plain cylindrical or conical section (much like a lamp shade) to a more complex cut sometimes called a petal, tulip or flower hood (as shown in some of the pictures), which produce a reasonable good shade without blocking the field of view
Field of view
The field of view is the extent of the observable world that is seen at any given moment....

 of the lens and thus producing vignetting
Vignetting
In photography and optics, vignetting  is a reduction of an image's brightness or saturation at the periphery compared to the image center. The word vignette, from the same root as vine, originally referred to a decorative border in a book. Later, the word came to be used for a photographic...

. Properly petal shaped lens hoods produce more shade than normal lens hoods with the same end diameter. Square lens hoods may be even better.

Lens hoods are more prominent in long focus lenses because the field of view has a smaller viewing angle
Angle of view
In photography, angle of view describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the more general term field of view....

 than of wide-angle lens
Wide-angle lens
From a design perspective, a wide angle lens is one that projects a substantially larger image circle than would be typical for a standard design lens of the same focal length; this enables either large tilt & shift movements with a view camera, or lenses with wide fields of view.More informally,...

es. For wide angle lenses, the length of the hood (away from the end of the lens) cannot be as long as those for telephoto lenses because of the viewing angle.

Lens hoods are often designed to fit onto the matching lens facing either forward, for normal use, or backwards, so that the hood may be stored with the lens without occupying much additional space. Some lens hoods are flexible and collapse for storage.

In addition, they offer some physical protection for the lens due to the hood extending farther than the lens itself.

See also

  • Lens cover
    Lens cover
    A lens cover or lens cap provides protection from scratches and minor collisions for camera and camcorder lenses. Lens covers come standard with most cameras and lenses...

  • Matte box
    Matte box
    In still photography and video, a matte box is a device used on the end of a lens to block the sun or other light source in order to prevent glare and lens flare...

     – similar, adjustable device used in still photography and video
  • Barn doors – similar device used for stage lights

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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