Lens Type

Although there are many varieties of lenses, common lens types include telephoto, wideangle, zoom, and prime. All of these lenses perform the same basic function: they capture the reflective light from the subject and focus it on the image sensor. However, the way they transmit the light differs.
Note:
Although there are several subcategories and hybrids of these lens types, these are the most basic.

Telephoto
A telephoto lens is a lens with a long focal length that magnifies the subject. Telephoto lenses are typically used by sports and nature photographers who shoot their subjects from great distances. Telephoto lenses are also used by photographers who want greater control over limiting the depth of field (the area of an image in focus). The larger aperture settings, combined with the long focal lengths of telephoto lenses, can limit the depth of field to a small area (either the foreground, middle, or background of the image). Small aperture settings, combined with long focal lengths, make objects in the foreground and background seem closer together.

Wide-Angle
A wide-angle lens is a lens with a short focal length that takes in a wide view. Wideangle lenses are typically used when the subject is in the extreme foreground and the photographer wants the background in focus as well. Traditionally, the focal length of a wide-angle lens is smaller than the image plane. However, in the digital photography age, the sizes of image sensors vary, and the lens multiplication factors of most DSLRs
increase the focal length. Check the specifications of your camera to ascertain the size of your digital image sensor. If the size of your digital image sensor is 28 mm, you require a lens with a focal length less than 28 mm to achieve a wide-angle view.

Zoom
A zoom lens, also known as an optical zoom lens, has the mechanical capacity to change its focal length. A zoom lens can be extremely convenient, because many zoom lenses can change their focal lengths from wide-angle to standard and from standard to zoom. This eliminates the need to carry and change multiple lenses while shooting a subject or project. However, because of the movement between focal lengths, the
f-stops aren’t always entirely accurate. To achieve a greater level of accuracy with apertures, many manufacturers have multiple minimum aperture values as the lens moves from a shorter focal length to a longer one. This makes the lens slower at longer focal lengths. (See “Understanding Lens Speed” on page 15 for an explanation of lens speed.) Plus, a zoom lens requires additional glass elements to correctly focus the light at different focal lengths. It is desirable to have the light pass through the least amount of glass in order to obtain the highest-quality image possible.

Prime
A prime lens, also known as a fixed lens, has a fixed focal length that is not modifiable. Prime lenses often have wider maximum apertures, making them faster. Wider apertures allow for brighter images in low-light situations, as well as greater control over depth of field. Prime lenses are primarily used by portrait photographers.

Focal Legth

An important attribute of a lens, besides its quality, is its focal length. Focal length is technically defined as the distance from the part of the optical path where the light rays converge to the point where the light rays passing through the lens are focused onto the image plane—or the digital image sensor. This distance is usually measured in millimeters. From a practical point of view, focal length can be thought of as the amount of magnification of the lens. The longer the focal length, the more the lens magnifies the scene. In addition to magnification, the focal length determines the perspective and compression of the scene.

DSLR - Digital Single Lens Reflection

This is the most popular camera type among the photographers.This camera is named for the reflexing mirror that allows you to frame the image through the lens prior to capturing the image. As light passes through the DSLR camera’s lens, it falls onto a reflexing mirror and then passes through a prism to the viewfinder. The viewfinder image corresponds to the actual image area. When the picture is taken, the mirror reflexes, or moves up and out of the way, allowing the open shutter to expose the digital image sensor, which captures the image. Most features on a DSLR are adjustable, allowing for greater control over the captured image. Most DSLR cameras also allow the use of interchangeable lenses, meaning you can swap lenses of different focal lengths on the same camera body.

Depth Of field

In photography one of the most important thing we should concider is Depth of field.When a particular subject is recorded on photographic media, some other entities present in front and at the back of the main subject are also recorded apparently sharp.The subject range that renders apparently
sharp on photographic media is know as the depth of field.This is based on the smallest entity that human eye can resolve - known as the circle of confusion.

There are three main parameters available to the photographer to control depth of field.

• The iris diameter of aperture. As the iris diameter reduces, the viewing angle of the light cone also is restricted, in creasing the DOF.
• The subject distance. Similarly increased subject distance also makes the projected angle on the lens narrower, increasing DOF.
• The focal-length of the lens used. Since shorter focal-length looks at a wider angle (large no. of picture elements), per element projected angle is narrower.

Shallow depth of field

Only the foreground is in focus.

Great depth of field

The image is in focus from the

foreground to the background.

Portrait Photography

Simply portraiture(Portrait photography) is photography of single person or group of people that displays the expression, personality, and mood of the subject. Like other types of portraiture, the focus of the photograph is usually the person's face and the required part of the face which we want to expose the feeling, although the entire body and the background or context may be included.

Wide angle Photography

Wide angle photography uses to expose large rage of area. For that wide angle lenses are very essential.In photography and cinematography, a wide-angle lens refers to a lens whose focal length is substantially smaller than the focal length of a normal lens for a given film plane

Macro Photography

Macro 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 (though macrophotography technically refers to the art of making very large photographs). By some definitions, 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.