Lenses the Goss

To capture an image on the sensore, light rays are captured by the camera censor.

Lenses are comprised of an elaborate series of glass elements held within an engineered housing.

Lights is transmitted through the lens and interpreted by the film or sensor.

Most modern lenses are based on a convex lens, thicker and one end and wider at the other end.

A and D are two halves of the convex lens. B and c are colour-correcting elements placed between.

Zoom lens most popular, but to get what you see, use a 50mm lens (35mm equiv) when starting to learn about photography. 

This type of lens is called a normal lens for 45mm film as it provides a normal point of viewasdf 

Where does this focal length come from...

Short focal length = wide angle lens. 

35mm filmed. Sensor size variation: large sensor requires larges lens to ensure all surface of image censor covered. Handy reference point. 

Zoom vs Prime

The primary advantages of prime lenses are in cost, weight and speed. Inexpensive prime lens can generally provide a good (or better) image then a high-end zoom lens. 

If using only a small fraction of focal length range then a prime lens with a similar focal length will be significantly smaller and ligher. 

The best prime lenses almost always offer a better light-gathering ability (larger maximum aperture) than the fastest zoom ability. 

Digital Lenses

Specific digital lenses - film can be properly exposed with light falling on it at any angle. 

An image sensor consists of a matrix of light-gathering photo sites set in "wells." This construction means light falls on it at a right angle.

Focal length Multiplier - Read more at Wikipedia

Normal Lens - Approximates the impression of human vision. The relative size of near and far objects seem normal. About the same in length as the diagonal measurement of the 'film.'

Prime - Good for low light, fast, easy, portable, light-weight.

Zoom-Lenses / Prime - Don't open so wide, are limited to the light they can gather.

"The normal lens gives the photograph an 'everyday' look, very suitable for everyday life. 

Shorter Lens

Increases the angle of view and shows more of a scene than a normal lens from the same position. It is commonly called a wide angle lens. A common wide angle lens is a 28mm. 

A wide angle lens is useful for photojournalism, as it allows the photographer to include the contextual information. It also offers unusual distortion effects. 

Longer Lenses

Greater image magnification. Commonly called a telephoto lens. Narrower angle of view than normal lenses. Less DOF. Anything longer than 70mm (bigger number) is a telephoto lens for 35mm film. 

These lenses appears to flatten the space. 

Zoom and Telephoto Lenses are not the same... ? Zoom lenses contain lots of different focal lengths in one.

Adv and Disadvantages of zoom lenses

Great travel lenses, They save wear and tear on lens mounts. Are typically more expensive and heavuer than fixed focal length lenses.