Bellows , a concept that comes from Latin follis, can be used to refer to device which allows to accumulate air and then expel it in a specific direction. These instruments usually consist of a container with flexible skin at its sides, a valve that allows the entry of air and a cannon through which, when the sides are folded and the volume of the device is reduced, the air comes out.
The bellows, in short, are mechanical appliances that store air for later, when subjected to a certain Pressure , eject it with a certain purpose. This object inflates when the air enters its structure and deflates when it is fired.
Usually the bellows has a valve which prevents the return of the expelled air, although it can also have different openings for entry and exit. Its operation is similar to that of a pneumatic pump.
In the field of metallurgy bellows are used to blow air into the fuel, increasing the amount of heat and the level of combustion. The forge which is used at forge Metals, for example, have a bellows to fan the fire.
Musical instruments like the bandoneon , he accordion , he pipe organ and certain bagpipes They also have bellows. In these cases, the device contributes to provide air or to regulate the one that the musician expels blowing.
In the field of Photography Finally, the bellows is a accessory which is used in certain cameras to favor the movement of the lenses and facilitate the focus. These bellows, which fold and expand as needed, generate a dark space between the lenses and the film or plate.
Bellows are part of a group of accessories in which the extension tubes or rings are also found. It is an ideal complement to the objectives used to do approach photographs . It is known as approach photography or of approach to the one that brings the object closer and makes it bigger, thus improving the appreciation of its details by the observer. Thanks to this type of capture, the human being can see certain features of the world around him that usually go unnoticed by him.
Although bellows and extension tubes are different parts, each with its characteristics and purposes, its operation is quite similar. For example, the two are located between the lens and the camera so that the distance between the focal plane and the subject to be captured increases. Through its use you can descend below the minimum distance limit of focus , thanks to which the object occupies more space than it would normally occupy.
One of the main differences between the tubes and the extension bellows is that the latter allow the user to adjust the degree of separation between the lens and the camera body. For this they usually have a mechanism of great precision that consists of some metal bars on which the objective every time we turn knobs in the desired direction, as we wish to zoom in or out.
Something that both accessories have in common is that they can preserve the automatic characteristics of the camera, although this varies according to the model and has a considerable impact on the price. Extension bellows are marketed with a plug that allows a double trigger cable to be inserted, which drives the shutter and the diaphragm at the same time, so that the diaphragm can be kept open to focus and close it at the time of shooting.