Aperture, Exposure and Depth of Field
Photography"Photography" is derived from the Greek words- photos ("light") and graphein ("to draw").THE FIRST PHOTOGRAPH:- On a summer day in 1827, Joseph Nicephore Niepce made the first photographic image with a camera obscura.
CAMERAFor photography, the most essential thing is camera.The camera is a wonderful little instrument for producing pictures. It is a light- tight box with a lens fitted in the front. It is made of die- cast sheet metal or some synthetic material and is light tight, usually covered with leather or plastic to give good finish. It is made to open from the back.
Most of the cameras consist of the following four main parts BODY, LENS, SHUTTER, VIEW-FINDER.Any camera is basically a light- tight box with a lens, which is often in a focusing mechanism. The lens has an aperture that controls the amount of light entering the camera. A shutter controls the duration of the light exposure, and a viewfinder allows for both composition and focusing.
HOW THE CAMERA WORKSLens: This gathers light reflecting from the subject, converging each ray so that it forms a point on the focal plane. The image is inverted during the process.Aperture: Like the Iris of the eye, the size of the aperture can usually be varied to alter how much light reaches the film/ chip. The aperture is fixed on the basic cameras.Shutter: This controls the amount of time the film or chip is exposed to the light. Usually it opens for a fraction of second, but exposures can last for hours.Focal plane: This is the flat surface where the image is either recorded on film or is turned into an electrical signal by a digital chip.
Aperture, Exposureand Depth of Field
The EyeIris changes the amount of light entering the eye (A)
Lens can change shape to focus (B)
Light sensitive area where an image is formed (C)
The CameraCameras are very similar to eyes:
Light sensitive area film or digital sensorLenses Instead of changing shape, they move closer or further away to the light sensor.Aperture in the lens controls the amount of light reaching the light sensorA shutter also opens and closes to let the right amount of light fall on the light sensor and get a correctly exposed image
Types of Lenses for 35mm camerasRemovable for SLR camerasFixed on compact cameras
Prime Lens (Fixed focal length)Zoom most common(Range of focal lengths)
9Look at your lens / camera who has a prime lens?Who has a zoom?
What does Focal Length mean?
Wide Angle = large field of view (focal lengths under 50mm)
Standard (50mm) = same perspective as the human eye
Telephoto = high magnification (focal lengths over 50mm)
ApertureWe can use the Aperture to change the amount of light entering the camera
To describe aperture we use f/stops and these have an f number.
e.g. f2, f2.8, f4, f5.6, f8, f11, f16, f22
ApertureSmall Apertures (e.g. f11, f16, f22) only let a small amount of light through
Large Apertures(e.g. f4, f5.6, f8) let through a lot of light
So for a sunny day you might need to use a small aperture to get the correct exposure
ApertureEach change of f/stop either halves or doubles amount of light entering the camera
The largest f/stop on a lens is called the maximum aperture. The maximum lens aperture is important because it indicates the largest amount of light that the lens will transmitA smaller maximum aperture f number (= a larger aperture) = a brighter lens = generally more expensive
13What is the maximum aperture on your lens?Who has less than f2.8?f2.8?f3.5? half stopF4?Over f4?Larger maximum apertures mean you can shoot in lower lighting conditions.
Depth of FieldChanging the aperture of a camera also changes the amount of the image that is in focus this amount is called the depth of field
Depth of Field
Depth of field can vary between shallow and deep
Large Apertures give shallow depths of field (small f numbers)
Small Apertures give deep depths of field(large f numbers)
Depth of FieldApart from using aperture, the DOF can also be changed by varying:
Focal Length (varying magnification)
Exposure / Shutter SpeedIn many cameras a physical shutter will open for a small length of time then close.
This allows the film or digital sensor to receive light for an exposure.
In digital compact cameras (and video cameras) the shutter may be electronic, which is where the sensor is only receptive to light for the shutter period
Exposure / Shutter SpeedThe effect of varying shutter speed while keeping a constant aperture:
The images start underexposed (too dark) with ashort exposure, are correctly exposed around 4s,and become overexposed (too bright) at 15s+
Exposure / Shutter SpeedA fast shutter speed (creating a short exposure of the film/sensor) is required to freeze motion (e.g. 1/1000s)
A slow shutter speed (creating a long exposure) can blur motion for interesting effects(e.g. 1/15s )
Shutter SpeedVery long exposures (30 seconds+) may be required in low light, but this can produce nice effects look at the sea.
ReciprocityChanging the shutter speed by +/-1 increment changes the exposure value by 1 stop (e.g. 1/30s to 1/60s )Changing the aperture by +/- 1 increment also changes the exposure value by 1 stop (e.g. f11 to f8 )
As these changes are equivalent, it means that there are a number of combinations that will give a correct exposure.e.g. 1/30s @ f11 = 1/60s @ f8 = 1/125s @ f5.6...
Under or over exposure?
What Is a Scene?A combination of shots that shoes the action that takes place in one location or setting
What Is a Shot?A continuous view filmed from one perspective
Shot DescriptionsCamera framingHow close or far a subject is from the cameraCamera anglesAngling of the camera from which you view the subject.Camera movementThe movement of the camera forward, backward, left, right, up, and down
Camera FramingExtreme long shotLong shotFull shotMedium shot Close-up shot
Extreme Long ShotEstablishes the location or settingExample: Western landscape
Long ShotShows the location, characters, and actionExample: soccer field and its players
Full ShotFrames the entire height of a person, with the head near the top of the frame and the feet near the bottom
Medium ShotFrames an individual from either the waist up, or from the knees showing the audience just enough to feel as if they are looking at the whole subject
Close-up ShotShows a character from the shoulders to the top of the head
Camera AnglesHigh-angle shotLow-angle shotEye-level shotBirds eye viewCanted shotTilt ShotThree-quarter shotOver-the-shoulder shot
High-angle ShotA camera placed higher than the subject (not directly overhead) and tilted downward
Low-angle ShotA camera placed lower than the subject and tilted upward
Eye-level ShotThe camera is positioned at eye-level with a character.
Birds Eye ViewThe camera is positioned directly overhead of the action
Canted ShotThe camera is tilted so that the subject appears to be diagonal and off-balance.
Tilt ShotA fixed camera that moves on it vertical axis, tilting up or down
Over-the-shoulder ShotPositions the camera over the shoulder of one character, revealing part of the backside of their head and shoulders in the foreground, and focuses on the character facing the camera in the background
Camera MovementPan shotCrane shotDolly shotTracking shotZoomZolly shot
Pan ShotA fixed camera pivots on its axis turning from left to right for the purpose of following the action within a shot
Crane ShotA camera positioned on a crane can swoop down or up covering great distances and producing unusual camera angles.
Dolly ShotThe camera moves toward a subject (dolly-in) or away from a subject (dolly-out).
Tracking ShotThe camera tracks alongside of the object or person.
Zoom ShotCamera stays stationary as the focal length of a lens zooms in or out.Framing gets tighter if the camera zooms in.Framing gets looser if the camera zooms out.
Dolly ShotA dolly shot in combination with a zoom
What is ISO?
ISO is short for International Organizational Standard. In the photographic world, ISO is most commonly referred to as a film rating system. Think film photography, not the movies. In terms of film, ISO is used as a rating system to tell you how sensitive the film is to light, or how fast the film is. The lower the ISO number (i.e. 50) the more time the film needs to be exposed. The faster the ISO film speed, less light is required to take a picture.
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