camera lens

CAMERA LENS

Presented By:-

RAJANISH KUMAWAT

10ESOEC092

4TH YEAR, VIITH SEM

APRACTICAL TRAINING

ATDOORDARSHAN KENDRA, JAIPUR

Topic Covered:-

DOORDARSHAN

KEY ASPECTS:-

Doordarshan is an Indian public service broadcaster. It is owned and operated by Prasar Bharati Broadcasting Corporation. It is one of the largest broadcasting organisations in India in terms

of the studio and transmitter infrastructure. It was started in Delhi on 15 September 1959 as experimental,

and its regular transmission started in 1965. Its Head office is located in New Delhi, India.

KEY ASPECTS:-

The DD provides television, radio, online and mobile services throughout India. 

Presently, Doordarshan operates 21 channels including DD National, DD News and DD Sports.

The network features some original programming, such as dramas, comedy-series, talk shows and re-runs of popular TV shows from other Indian television channels. Live Coverage of national events like Independence Day, Republic Day Celebrations, Budget Presentation and other happenings of national and international importance are regularly carried on this channel.

DD RAJASTHAN

KEY ASPECTS:-

DD Rajasthan is a state owned TV channel telecasting from Doordarshan Kendra Rajasthan.

On 1 August 1975, the first television broadcast was viewed by the people of Rajasthan under the Satellite

Doordarshan Kendra in Jaipur was set up on 1 June 1987 at Jhalana Doongri and transmission started on 6 July 1987.

Initially only 30 minutes of programming produced by this Kendra and this was gradually increased. Presently the

Kendra originates about four hours of programming daily. The channel covers 79% by population and 72% by area of

Rajasthan.

DOORDARSHAN RAJASTHAN

A TV Camera consists of three sections:-

a)A Camera lens: It selects a certain field of view and produces a

small optical image of it on the face plate of pick up device.

b)A transducer or pick up device: To convert optical image into an

electrical signal. It is mounted inside the main head of camera.

c)View Finder:- It shows a small video image of what the lens is

seeing.

Television Camera lens

Topic of interest

FUNCTIONS OF LENSES:

Primary function of lens is to produce a sharp image of object on the face of camera imager.

To determine the magnification and size of the image.

To decide field of view.

NOTE:-Changing distance from the lens to object changes the size of the image and position of the image plane

objecto

objecto

objecto

Real image

Real image

Real image

lens

lens

lens

f

f

f

FOCAL LENGTH

Focal length is the distance between optical center of the lens (and not the physical center) and the focal point.

Focal point is the point at which the light rays converge at the rear of the lens to produce perfectly focused image.

In a video camera it is the distance between

face of the pick device and optical center of the

lens.

Focal length will decide the amount of image

magnification and field of view.

Wide angle

Narrow angle

Optical center

Image plane

Image plane

Focal length

Focal length

(Short)

(Large)

BASIC TERMS IN CAMERA LENSResolution: Number of pixels captured by image sensor.Focus: To focus objects at various distances

3,4,5,7,10,15,30, infinity, in feetZoom: To take long(lowest focal length) and tight shot (Highest focal length)Aperture: To control the amount of light entering

cameraF-stop: 1.4, 2.0, 2.8, 4, 5.6, 8, 11, 16, 22, Back Focus: To keep long shot in focus while zooming out.Macro: To focus an object lying within Minimum Object Distance.

Resolution: Resolution is number of pixels captured by the image sensor.

Higher Resolution Image300 ppi

Lower Resolution Image72 ppi

SHUTTER

All cameras have a shutter between the lenses at the front and the film at the back.

The shutter is mostly closed so that light cannot get to the film.

When you press the button to take the photo, the shutter opens briefly and then closes again.

The time for which the shutter is open is called the shutter speed. The shorter the time, the less light gets in.

So, a shutter speed of 1/60th of a second

lets in half the amount of light than a speed of 1/30th of a second.

Focus

Poor focus Poor focus

Average focus Good focus

Variable Focal Length Lens or Zoom lens

Zoom lens has variable focal length and changes focal length continuously without losing focusing . Typical zoom range from 12-72mm.

Zoom Ratio 6:1 can also be expressed as 6x. The zoom ratio can be 10x, 12x, 15x, 19x etc.

The greater the focal length, the narrower will be the field of view and the narrower the depth of field.

Action of Zoom Lens

Focal length 165mmFocal length 80mm

Focal length 40mmFocal length 8.7mm

APERTURE

Aperture is required to control the amount of light entering the camera.

The amount of light is specified by F-number (=f/D).

The stop ring of the lens is marked with series of numbers with a ratio of under-root of 2: 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22

Aperture with various openingsFully Closed

Fully Open

Partially open

Half open

F-stop=2.8 F-stop=4.0

F-stop=5.6 F-stop=8.0

Effect of Aperture (Iris)

F-stop=11 F-stop=16

F-stop=22 Iris Fully Closed

Effect of Aperture (Iris)

Maximum to minimum distance within which the objects remain in focus

With aperture fully opened With aperture partially open

Depth of field

Lens Aperture: Smaller the aperture or larger the f-stop number, more the depth of field. It is because with less aperture opening the light rays from the outer edges of lens are cut off, narrowing the maximum convergence angle at the focal point.

Camera to subject distance: Larger the distance of the subject from the camera, greater is the depth of the field

Focal length of the lens: As you increase the focal length of the lens (i.e. narrowing it’s angle of view), the image size increases, but the relative depth of field decreases. Lens stop and focusing distance remaining constant.

Factor Affecting Depth of Field

Close-up or Macro lens enables us to take photographs of the objects closer than MOD. In Macro mode, zoom lenses cannot zoom.

MACRO

Without macro With macro

Wide Converter

A wide converter is useful for getting a large number of people into one scene in a narrow space

Close-Up Lens

A close-up lens is effective for close-up photography of, for example, flowers and insects.

UV Filter, Skylight filter

A UV (ultraviolet) filter is nearly colorless. It absorbs short-wavelength ultraviolet rays that the naked eyes cannot see.

Extender

Extender is mounted between the camera and the lens to enlarge the images of the subjects, or shoot more distant subjects