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SLR Photography. Camera Settings and Exposure. What is exposure?.
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SLR Photography Camera Settings and Exposure
What is exposure? • In photography, exposure is the total amount of light allowed to fall on the film (or electronic sensor in the case of digital photography) during the process of taking a photograph. Exposure is measured in exposure value (ev), with higher values denoting more light.
How is exposure controlled? • Three factors control the exposure of the image: • Shutter Speed • Aperture (f-stop) • Film Speed (ISO)
Shutter Speed • Shutter speed refers to how long the camera shutter opens up to let light in. It is expressed in fractions of a second or full seconds (i.e 1/60th, 1/500th, 1/1000th). • The higher the number, the faster the shutter. A faster shutter means less light is let in.
Shutter Speed • Fast shutter speeds are used to “freeze” the action, e.g. for sports or action photography. • Slow shutter speeds are used when a blurring effect is desired – e.g. for the classic “waterfall” shot or for nighttime traffic pictures.
Aperture • Aperture (or f-stop) refers to how much light is let into the camera. There are a series of blades built in to the camera lens that open and close to let more or less light in. • Aperture settings are standardized, and expressed as numbers such as 2.8, 4, 5.6, 8, 11. The lower the number, the wider the aperture/more light let in.
Aperture • Wider apertures cause a shallow “depth of field”. • Depth of field refers to the area of the photograph that is in full focus. • Wide apertures allow you to have an out of focus background for more aesthetically pleasing portraits.
Film Speed (ISO) • Film Speed refers to the sensitivity of the film or image sensor to light – that is, how fast it is able to capture the image. • Expressed in ISO numbers e.g. 50, 100, 200, 400, 800. • The higher the number, the faster the image is captured - faster film tends to be “grainier” though.
Setting Exposure • Automatic (P) – Camera Decides • Shutter Priority (Tv) – You set Shutter, camera sets Aperture • Aperture Priority (Av) – You set Aperture, camera sets Shutter • Full Manual (M) – You set both
Under and Over Exposure • Camera sets exposure based on 18% grey reflectiveness • Overexposure occurs when too much light is let in to camera – picture is bright • Underexposure occurs when not enough light is let in – picture is dark
Difficult Exposure Situations • Subject in front of bright window – hard to get even exposure (subject too dark or background too bright) • Taking pictures on snow or ice – Camera is fooled, snow may look greyish.