Final Cut A Decent Exposure BY JILL HEINERTH M y old Nikonos V
underwater camera had a big green ‘A’ on the dial. Most people never moved that dial off of the ‘A’ position except to switch it to the familiar red ‘R’
that allowed you to rewind the film safely back into its lightproof metal canister. It is hard to believe that I gave up that camera only a decade ago. Well, “gave up” is a generous term. All of my prized underwater camera gear was stolen on the night of the wrap party, after a long gig on the Hollywood movie ‘The Cave’. We were all on the beach drowning in tequila while the (so-called) security guard for our lodging invited his friends to divest our rooms of all our valuables.
As a result, I was reluctantly torn from my love affair with film emulsion and thrust into digital cameras in 2005. My new Nikon dSLR had a familiar ‘A’ on the dial, but I had been long warned against using that setting. An early Nikonos V mentor told me that, ‘A’ stood for ‘Average’ and not ‘Automatic’, as I had understood. She clearly coached, “If you want to be truly creative you have to be smarter than the camera.” Howard Hall (another unknowing mentor) offered his best exposure advice, “f8 and be there!” I knew the wisdom resided somewhere in-between. My new camera had single-letter settings for Program, Aperture-Priority, Shutter-Priority and Manual. Clearly I was going to need to dig out my university notes and refresh myself in the theory of exposure if I wanted to be smarter than this camera. The good news is that whether you are a still photographer or videographer, the rules of exposure are the same and this single article holds many of the keys to understanding how different settings affect the look and feel of your still photos or video footage.
It Started with a Pinhole In the earliest days of image making, photographers used a device called a ‘pinhole camera’. This was simply a small box containing a flat plate of light- sensitive material or film. A tiny hole in the front of the box could be opened to allow light to strike the surface of the
60 Magazine Renee Power shooting
video on the Dori wreck in Sao Miguel, Azores
material. Larger holes allowed more light in and produced a brighter exposure. When the hole was held open for a long duration, it gave time for more light to strike the film plane. The actual image exposure was a relationship of light intensity and time. The intensity of the light was controlled by the size of the pinhole and the time was controlled by the duration that the shutter curtain was held open. Modern photographers express this relationship with an equation that forms the pivotal theory for all photography and videography: Exposure = Intensity x Time or E = I x T. The modern ‘pinhole’ is called the aperture. This opening, which allows light into the camera, controls the intensity of the light striking a sensor. It has also been referred to as an iris, since the opening works much like that of the human eye. Aperture openings are expressed as ‘f/stops’. Time is controlled by shutter speed, which can be selected in seconds or fractions of seconds. There are many equivalent exposures when mixing and matching different shutter speeds and apertures, and when you understand how they work together, you can change the
‘look’ of your images and footage dramatically.
Correlations
Aperture has the biggest effect on depth of field, or how much of the photo or footage in front of (and behind) the subject appears in sharp focus. Shutter speed affects sharpness, but in a different way. Slow shutter speeds tend to blur footage where fast ones freeze motion in a still photograph, or create sharp edges in video footage. Finally, ISO affects graininess, which we refer to as gain or colour noise in digital shooting. ISO selection helps us to support the best combination of aperture and shutter speed but can result in declining quality as the ISO number gets higher. (ISO was formerly called ‘Film Speed’.)
Exposure Triangle
The following chart is a visual guide to understanding these interrelationships. Beware, it is going to take longer to ‘read’ and visualize the chart than it did to read this article itself! The good news is that by understanding how aperture, shutter speed and ISO work together, you will be smarter than your camera and able to deliver truly fresh and creative results.
Photo and Illustration: Jill Heinerth
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