Lens Cut-Away

Lenses can be manual or auto. Manual lenses are used in manual cameras and works with auto focus cameras as well, but only in manual mode, where as auto focus lenses can be used with manual cameras as well except for G series Nikon lenses which unfortunately don’t have an aperture ring and thus we cannot use them in manual cameras.

Lens Construction

A lens is made up of a lot of glass elements. Lens has an aperture or opening in it, which is made up of a number of overlapping blades called as diaphragm, through which light reaches the film.

We control the size of aperture, if light is low we can open up the aperture so that more light reaches the film, and if the light is more we can close the aperture.

Aperture is numbered as 1, 1.4, 2, 2.8, 4, 5.6,8,11,16,22 and henceforth.

Here each value is square root of 2 times more than the earlier. Each aperture allows double the light as its immediate precedent and vice-versa.

Then there is focusing ring on the lens through which we focus the image on to the film plane. This ring has markings on it, in ft and in meters and we can focus the subject and can see exactly how far is subject from us.

With the help of aperture we can also control the depth of field, which is the zone of sharpness in front and back of the subject. When we close down the aperture the depth of field is more and when we open up our aperture depth of field is less.

In lenses of medium format cameras besides the aperture, the shutter is also inbuilt in the lens itself and is called in between the lens shutter or compour shutter. The advantage of such shutter is that we can sync the flash at all the available shutter speeds

Lenses are classified as -----

FIXED LENSES

ZOOM LENSES

Fixed lenses have a particular focal length and work for that particular focal length only .The advantage of such lenses is that they are quite fast and are of extreme good quality.

400 MM Fixed Lens

Zoom lenses have a range of focal lengths available and work at a number of focal lengths e.g.: 28-105,80-400mm.with advancements in technology some zoom lenses have even reached a level of quality equivalent to what we get from fixed lenses, if not better.

Zoom Lens

There are a lot of lenses available in market today -----

NORMAL LENSES
Here the focal length of lens is equivalent to diagonal of negative it produces
E.g.: 24 by 36 = 48.5~50mm lens
6 by 7 =110mm

WIDE ANGLE LENSES
Here the focal length of lens is smaller than the diagonal of negative it produces e.g.: 17mm, 20mm, 28mm, 35mm etc.

Wide Angle Lens

TELE PHOTO LENSES
Here the focal length of the lens is greater than the diagonal of negative it produces eg: 135mm, 200mm, 300mm, 400mm etc.

Then there are lenses available for particular needs -----

MACRO LENSES
In these lenses the minimum focusing distance between the subject and camera is extremely low and we can go much closer to our subject as compare to other lenses.

FISH EYE LENSES
these are the lenses where the angle of view of the lens is nearly 180 degree. But the problem with such lenses is the huge amount of distortion we get. E.g.: 6mm or 7mm.

PC LENS
Perspective control lens –These are the lenses generally used for architectural work.
Generally when we shoot any building or monument from the base of the building with our lens, there is some amount of distortion or converging of the top corners of the image is there .to avoid the, we use pc lenses where we can shift the lens to get rid of this distortion and there is no distortion in our image.
Pc lenses work on the same principle as the bellow system of large format cameras work where also to get rid of distortion we give camera moments.

PC Lens

MIRROR LENSES
As the lenses are made up of a lot glass elements, the long lenses become heavy and it becomes too difficult to hold them and shoot .so, these mirror lenses came up where instead of glass elements there are reflective mirrors in the lens from which the light bounces and reaches the film plane.