LENSES

the definitions of lenses .

(IN TERMS OF Device, Eye, Metaphor, Plant)

• A transparent optical device used to converge or diverge transmitted light and to form image.

• Genus of small erect or climbing herbs with pinnate leaves and small inconspicuous white flowers and small flattened pods: lentils

• (metaphor) a channel through which something can be seen or understood; "the writer is the lens through which history can be seen".

• Biconvex transparent body situated behind the iris in the eye; its role (along with the cornea) is to focuses light on the retina.

• Electronic equipment that uses a magnetic or electric field in order to focus a beam of electrons

DEFINITION

In term of photography , the lens can be define as the part of the digital camera or video recorder that concentrates light and focuses the image. The lens itself is a single piece of glass (or other transparent materials) with one or more curved surfaces. Cameras usually contain a combination of lenses that receive light rays from an object and form an image on the focal plane. Most digital camera have a fixed zoom length that can’t be removed / replaced while DSLR camera has a removable lenses.

FOCAL LENGTH

The focal length of the lens is then defined as the distance from the middle of the lens to its focal point. The focal length of a lens is usually displayed on the lens barrel. Below is a picture of a Canon lens with a focal length of 50mm. The maximum aperture is f/1.8.

Lenses are usually categorized as having a wide-angle, normal or telephoto focal length. A normal SLR lens covers a 24x36mm film frame with a field of view that corresponds approximately to our normal vision; a lens with a focal length of 50mm (55mm is also popular) is considered as normal.

Any lens with a focal length less than 50mm (or 55mm) can be considered as wide-angle; any lens with a focal length greater than 50mm (or 55mm) can be considered a telephoto. A zoom lens offers a range of focal lengths (12x).

MACRO LENSE

Macro photography is close-up photography of usually very small subjects.

Nikon, Canon and Sigma macro lens

If you're looking to purchase a macro lens for the first time, it's easy to get confused by the range that is available. For Canon Digital SLR camera's, there are 3 popular choices.

• Canon EF 100mm f/2.8 Macro USM Lens
• Canon EF-S 60mm f/2.8 Macro USM Lens
• SIGMA 50mm f2.8 EX Macro 1:1 Lens for Canon SLR digital camera's

For photographers who use Nikon SLR camera's, there is:

• Nikon 105mm f/2.8G ED-IF AF-S VR Micro-Nikkor Lens
• Nikon 60mm f/2.8D AF Micro-Nikkor Lens
• Sigma 50mm f/2.8 EX DG Macro Lens for Nikon SLR Cameras

PRIME LENSE

A prime lens is one that has just one focal length only (in contrast to a zoom lens that covers a wider range of lengths). It is a fixed focal length lens, like 24mm or 85mm.Prime lenses come in a wide range of focal lengths from wide angles through to the very longest of tele-photo lenses used by many sports photographers and paparazzi.While zoom lenses are ever popular and come as the standard kit lens with most DSLRs sold – prime lenses remain the favorite of many.

Some of the reasons why many photographer uses this lense.

Maximum Aperture – one of the biggest arguments used by prime lens lovers is the speed that prime lenses are able to offer. For example, in the Canon range the fastest lenses available are all prime lenses (down to f/1.2) where as in the zoom range f/2.8 is as fast as you’ll get.

Quality – traditionally prime lenses are known for their advanced optics and quality. They generally have less moving parts and so manufacturers are able to concentrate their efforts on adding quality glass and meanisms.

Price – in general prime lenses are simpler in terms of construction and as a result they can be cheaper to buy. Of course it’s not as simple as this and quality is determined by many factors and as a result price varies a lot even in the prime lens range of most manufacturers.

Weight – once again, a simple lens with less moving parts can mean that in many cases prime lenses are smaller and lighter than zooms.

Prime Lenses Combat Lazy Photographer Syndrome – when you have a zoom lens attached to your camera the temptation is to let your zoom do all the work and to leave your feet attached to the same piece of turf. This is what is attractive about zooms – however it can also lead to laziness and I’ve heard a few prime lens users argue that when they have a prime lens attached that it makes them more creative with their framing as they are forced to look more actively for the best shot