Aperture & Shutter Speed.ppt

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The focal length of the lens determines the angle of view

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28mm

43mm

43mm

Telephoto or Long Lenses Bring things closer 28mm

43mm

135mm

A fast long lens. Note the large diameter front element designed for gathering lots of light.

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Wide angle or wide lenses Enable you to get more into the picture

50mm lens

Features of wide angle lenses

17mm lens

Wide angle

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Gives a wide angle of view •
A tendency to distort near the edges •
Increases the apparent relative distance between objects •
More •
susceptible to flair •
Small and light compared to long lenses •
Increased depth of field

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Wide angle

Lenses are described as fast or slow A fast lens is one that allows lots of light to pass through it. It will be physically wider in diameter than a slow lens. Probably bigger, heavier and certainly more expensive than the slow lens.

Distortion

However It may not be as sharp when used wide open As the boundaries of performance are pushed so the price increases (usually exponentially)!

The aperture

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Aperture Termed

f

number

or

Stops Each stop is

The variable diameter diaphragm used to control the amount of light passing through the lens and on to the CCD or sensor

f stop values are represented in the following way




or

twice

as much light

and is derived from a mathematical formula describing the amount of light passing through the lens for a given period of time

How the aperture works

Typical standard values

f 2 f 2.8 f 4 f 5.6 f 8 f 11 f 16 f 22 f32

Each one of these values is half or twice the amount of light f 2 being the maximum and f 32 the minimum in this sequence

Aperture

The shutter may be configured as a variable width blind

Shutter Speed Controls the length of time that the sensor is exposed to light Travelling across the sensor face at a set speed. The width of the blind governing the relative amount of time the sensor is exposed to light. The wider the blind width the greater the amount of light reaching the sensor. These are called focal plane shutters.

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1/125th. sec Conversely the blind may be of set width but the speed with which it travels across the sensor variable. 1/30th. sec 1/30th.

sec or

1/125th. sec

A simple shutter may consist of a sprung plate which passes across the lens

More sophisticated shutters have variable speed diaphragms which open and close. These are called leaf shutters

A more complex shutter might allow the speed of the passing plate to be varied.

Copal Press camera shutter

The relationship between shutter & aperture •
Both control the amount of light reaching the sensor

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The relationship between shutter & aperture

The relationship between shutter & aperture

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Both control the amount of light reaching the sensor

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Both control the amount of light reaching the sensor

•
The aperture effects the depth of field

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The aperture effects the depth of field •
That is the zone of focus How much is in focus in front and behind the object

The relationship between shutter & aperture •
Both control the amount of light reaching the sensor •
The shutter affects movement

The relationship between shutter & aperture

The relationship between shutter & aperture

•
Both control the amount of light reaching the sensor

•
Both control the amount of light reaching the sensor

•
The shutter affects movement

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The shutter affects movement

•
It can stop movement to keep objects sharp

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It can stop movement to keep objects sharp •
Or allow movement for effect

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Aperture to shutter speed

f4

f 5.6

f8

f 11

f 16

1/250

1/125

1/60

1/30

1/15

The exposure is expressed as a combination of the two. i.e.f8 at 1/60

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