Lens hood cuts off the extraneous light, entering the camera lens.
When we shoot a subject against light, the chances of unwanted light, entering the lens are increased. If the source of light is in the frame, then we cannot do anything about it, but if it is not in the image frame or composition, then also it can enter in the kens and reduce the contrast of the photograph in a noticeable manner.
This can be avoided with the help of a hood, that is designed to fit on a lens. A simple form of this hood can be a pipe or conical cylinder, which is to be screw mounted on the front ring of the lens. This type of hoods are generally made from a metal, but cheaper version of hoods are available, which are made from rubber. Both these hoods work equally well, but a rubber hood can be folded flat. This saves space when the camera is kept in the camera bag.
Better shape of a hood can be rectangular. This shape is more practical but irrespective of the shape, a hood must be used on a lens, for which it is designed.
There are some complex designs, which are in tulip petal shape. This shape is slightly better in performance as compared to the tubular shape, as it reduces any chance of vignetting at corners of photograph. These hoods are mainly used on zoom lenses.
A hood has to be specifically designed for a specific focal length. As focal length of a lens is directly related to angle of view and coverage, the hood must reach to the maximum length, which can shade extraneous light, but does not produce any vignette on corners. This means that a long focal length lenses can have a deeper hoods, whereas wide angle lenses should have a shallower hoods.
So when it comes to a zoom lens, there has to be some compromise. In such case, the hood is designed to perform best for wide angle focal length and will not perform as effectively as it should on longer focal lengths.
A professional version of hood is constructed with bellows, which can be adjusted for its length. We have to manually adjust the length for maximum shade in such a way, that there is no vignetting corners. This way we can maximize the shade on many focal length lens with one hood.
If we need to mount the hood on different lenses (with different lens diameter), there is a provision on hood mount. Some designs also provide a holder, on which we can fix a black rectangular cover to shade the sun.
Though it is a cheap accessory in photography. a good lens hood is most of the time indispensable.
Read more about:
Auto focus mechanism of camera
Depth of field
Flash light meter
Other photographic accessories
Studio flash lights
Types of cameras
Wide angle lens
Return back to accessories from lens hood
Return back to Home Page