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EXPOSURE The Science Behind the Lens

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Index

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The Triangle

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Camera Formats

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The Film Era

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ISO Sensitivity

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Shutter Speed

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Aperture

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Post Processing

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Portrait

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Still Life

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Landscape

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Sunset at the Princess Pier, Melbourne

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Craters of the Moon, New Zealand

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The Triangle Behind any incredible image is

a precise calculation of exposure. Exposure determines how light or dark a picture may appear and photographers can adjust this to suit their own tastes. Modern cameras have built in mechanisms called light meters, which give visual feedback to the photographer whether the image will turn out with a correct exposure. This can of course be tweaked by modifying three specific settings: ISO, aperture, and shutter speed. Together these elements combine to create what is known as the exposure triangle, the three defining points which determine the look and feel of any picture.

ISO sensitivity is the measurement of how sensitive the camera will be to light

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Aperture is decided by how narrow or wide the blades open inside a lens

Shutter speed is dictated by how fast or slow the camera curtain opens


The Gibson Steps along the Great Ocean Road

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Loch Ard Gorge, Port Campbell

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Camera Formats The most common variety of cameras

seen today is the 35mm format, which is the name given to cameras which can produce an image in a 3:2 aspect ratio. The canvas size to create the picture is generally 36mm x 24mm, which is classified as a full frame. Higher end digital cameras will use these measurements to form the size of the image sensor. The format originated in the 1920’s when the German engineer Oscar Barnack introduced the very first Leica camera. Prior to this, the most popular format used was medium format, which produced a larger image in the shape of a square. Medium format cameras are still used today and specialise in capturing stunning images with the capability to be cropped and still retain details, due to the often-high megapixel counts. Despite other formats, 35mm has proven to be the cinematic and photographic format of choice for many amateurs and professionals alike.

A typical medium format camera is generally more expensive than the 35mm format, and is larger in appearance

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35mm cameras are compact and perfect for everyday use, but struggle to produce the quality of image medium format does


Street candid during sunset at Melbourne’s Docklands

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The Grotto, Port Campbell

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The Film Era Before the introduction of digital

photography in 1975 by Kodak, film was the way to shoot. In a 35mm film camera it involves loading a roll of 135 film into the back of the camera, and each time the shutter is released, a curtain will move up and expose the film to light. This is when the aforementioned triangle of exposure comes into play. Particularly with film, since if you make a mistake, it’s permanent, it is important to achieve correct exposure first time, in camera. One of the most notable and perhaps most famous film photographers was Henri Cartier-Bresson. He shot almost exclusively in black and white, and used only lenses predominately with a 50mm focal length. This length gave him a similar perspective to the human eye, and allowed him to better compose and think about his shots.

Films are stored in airtight canisters to prolong shelf life. The film itself is wound around a spindle to stop potential exposure to stray light

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Film cameras that don’t have the ability to autofocus use split screens, where the image in the viewfinder is split until in complete focus via the lens


The Redwoods, Rotorua

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Black Rock Beach, Brighton

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ISO Sensitivity ISO stands for International Standards

Organisation, and it is the industry scale for measuring sensitivity to light. It is measured in numbers, and the higher the number, the more sensitive the sensor (or film) will be to light. Typically ISO’s can range anywhere from 50 all the way up to 409,600. It is important to recognise that when the ISO is pushed to the higher limits, artifacts will be introduced in the image. Blacks will appear crushed and specks of grain known as noise will be present. Unless intended, it is therefore recommended to keep the ISO at the lowest possible setting. Highend cameras can produce clean images at over 50,000 ISO, but definitions of useable images will always vary. Shooting at night is the most common time to use a high ISO, in order to freeze motion and keep a faster shutter speed. Low ISO’s can be used at night however if a tripod is involved to steady the camera and take a longer exposure.

Higher ISO ranges effectively allow dark skies to become brighter. Bumping the ISO up is therefore suitable for astrophotography 18

When increasing the ISO levels, so does the level of artefacts in the image. Grain known as noise will occur, but it can be removed in post


The dark skies of Waihi, New Zealand

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Tom and Eva lookout along the Great Ocean Road

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Shutter Speed Shutter speed is the next component

of the exposure triangle. Single-Lens Reflex cameras, or SLR’s, dictate shutter speed through a curtain, which moves itself up to expose the sensor or film. Long exposures leave the sensor exposed for longer, and portray movement in the final image. It also lets in more light, so the aperture and ISO settings must compensate to form the correct exposure. Shorter exposures freeze movement, as one would expect. Less light is let through, so ideally more light or suitable settings must be used. If you were looking to create a sharp image, your shutter speed should match or exceed your focal length. For example, a 50mm lens should have a minimum shutter speed of 1/50th of a second in order to create a shake free image.

Fast shutter speeds will freeze action without any blur. Keep in mind it will also let in less light so expose accordingly

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Slow shutter speeds will let in plenty of light, and portray movement. Make sure you have a tripod to keep the camera still


Steel wool portrait at the Grotto, Port Campbell

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The freeway to Apollo Bay

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Aperture The final and arguably most impactful

part of the exposure triangle is aperture. Aperture dictates the depth of field in a picture, and controls which elements are in or out of focus. The lens controls this value through metal blades, and specific lenses can only achieve a blurred out background, which is known as bokeh. Aperture values are measured in f-stops, the lower the f-stop, the larger the aperture opening and vice versa. A prime lens, which cannot zoom, will typically have an aperture of around f/1.8 to f/22. At f/1.8, the focal plane is very slim and only the subject that is focused on will be in sharp focus. This is useful for blurring out backgrounds and distractions. At f/22, the whole frame will be sharp; therefore higher aperture values are useful for shooting landscapes and situations where a larger plane of focus is required. Most lenses are typically at their sharpest overall around f/11, where elements such as diffraction and aberrations will not take away from image quality. When pointed into direct light such as the sun at a small apertures like f/16, a sun-star effect is made possible, where the light source takes on a star shape with the same number of points as there are aperture blades in the lens.

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Focus in the image is dependant on the aperture. Larger apertures means more in focus and smaller means less


Cliff-side portrait at the Twelve Apostles

The aperture blades open and close when adjusted. The amount of blades varies from lens to lens, and will dictate bokeh quality

The closer you stand to a subject, the more likely you are to create an out of focus background. Longer focal lengths help

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Hukka Falls, New Zealand

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Post Processing While the exposure triangle is a

crucial part of creating an image, post processing is equally important to reach the level of finish desired. In the digital age, this is made easy through processing software where various parameters can be tweaked to give almost unlimited creative potential. When shooting on film, the type of film used will often dictate the colours achieved in the final result, and the overall look and feel. Certain films will contain a higher grain or more saturated colours, while others may be black and white only. Shooting RAW in digital cameras enables photographers to capture the image just as the camera’s sensor sees it. This results in a larger file size, but an uncompressed image that optimal for post processing. Shooting JPEG format is convenient for instant sharing, but it is compressed by the camera and will often look worse than a correctly processed RAW file, which offers much more flexibility at the sacrifice of time.

Post processing can be done digitally via computer software such as Adobe Photoshop or Lightroom 30

Film is processed via a mixture of chemicals. Black and white films can be processed at home using a Patterson tank


Cliff-side portrait at the Twelve Apostles

The Great Lake Taupo, New Zealand

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Princess Pier, Melbourne

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Portrait Assignment #1

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Portrait Assignment #2

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Hobbiton, New Zealand

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Still Life Assignment #1

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Still Life Assignment #2

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The Redwoods, Rotorua

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Landscape Assignment #1

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Landscape Assignment #2

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Gibson Steps, Port Campbell

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Exposure An ISSUU Edition Kiran Raszka

Exposure  

The science behind the lens.

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