In photography , a wide-angle lens is one whose focal length is less than the normal lens , resulting in a viewing angle greater than human vision. It is used for panoramic views, and landscapes .
The viewing angles of this type of targets ranging from 60 to 180 °. The camera focal lengths of 35mm vary between 18 and 35mm. The brightness of the wide angle is usually high, reaching up to f2.8 (see f-number ).
Qualities
With lenses of this type is obtained:
- A greater depth of field in photography, why is commonly used in landscape photography where it is often important to portray many elements at close range.
- Cover major portion of scene from a distance of less (thanks to its wide viewing angle), which provides the photographer the power to take photographs of large objects up close. This is very common in indoor photography.
- Exaggerating the perspective of objects, causing a distortion of the more charged lines when the photographer comes to the subject. This quality is exploited commonly in architectural photography to reveal the grandeur of human constructions taking a contrapicado with a wide angle up close. On the other hand, precisely because of this effect, caution should be used with objects that are placed at the edges of the frame, since they will be "curved" or "pulled" distortion caused by the curvature of the lens.
Classification
Depending on focal length, wide angle lenses are divided into different groups:
Great angle or standard report
In the small format (35mm) range between 28 and 35mm focal length with diagonal viewing angles between 60 ° and 65 ° respectively. Because of its ability to cover a large amount of space at short distances, they have a large depth of field and distortion still relatively small, are frequently used in reportage photography. These angles are usually very bright targets. These angles are cheaper and are often found in the universal zoom (provided in most cameras).
- 28 mm diagonal angle: 60 °
- 35 mm diagonal angle: 65 °
Super wide-angle
They are wide-angle focal lengths less than 28 mm and a superior viewing angle of 80 °. These angles are usually used for fine art photography of nature and even naked , to achieve certain special effects that are obtained by the distortion of the image.
The super wide-angle objectives most common are:
- 24 mm (83 °)
- 20 mm (94 °)
- 17 mm (104 °)
Fish Eyes
The objective fisheye is a special form of super wide-angle, whose distortion (sometimes deliberate) is like a reflection in a sphere, reaching viewing angles of 180 °. There are two types: those that cover the entire display surface (film or sensor) thereby forming rectangular images, and those that form a circular image. In the most common small format are:
- 15 mm (180 °)
- 7.5 mm or 8 mm (circular image)
- Is Exot Nikkon objective of focal length 6 mm and 220 ° of vision. Form a circular image in which even reached back.
Limitations of design
In type cameras SLR , due to space required for movement of the mirror focal lengths are not possible "real" less than 50 mm, so that the construction of wide-angle lenses are used such techniques as retrofoco involving minor brightness, higher costs and greater size of the target.
The cameras DSLR (digital SLR) a further limitation arises because the sensor CCD or CMOS is usually smaller than that of film cameras. Therefore, the sensor only captures a portion of the image produced by the lens. This image trimming implies a lower viewing angle, due to which a wide-angle lens becomes 28 mm normal lens when mounted on a digital camera with 1.6 multiplication factor.
To use wide angle digital SLR cameras multiplication factor in most cases it is necessary to use lenses designed specifically for these cameras.
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