PHOTO TECHNIQUES
CANON EOS CAMERA SKILLS
Learn all you need to know to take better exposures Apertures • Shutter speeds • ISO • Depth of field
The exposure triangle
Aperture, shutter speed and ISO work together in harmony to produce the right exposure for you
IMAGINE that aperture, shutter speed and ISO are three sides of a triangle. If we alter one element, then we have to compensate by adjusting at least one of the other two. For example, a wide aperture and a short shutter speed might produce the same exposure as a narrow aperture with a longer shutter speed, but the resulting images are different.
Widening the aperture allows more light through the lens, so we compensate either with a shorter shutter speed to keep the capture of light brief, or a low ISO to make the sensor less sensitive to the light that hits it.
The longer the shutter is open, the more light shines through. So, to prevent overexposure, we compensate either by narrowing the aperture to reduce the light, or by lowering the ISO to make the sensor less sensitive to light. A narrow aperture restricts the input of light and produces images with greater depth of field, often desirable for landscapes, but this results in slower shutter speeds. For action shots, you want a wide aperture and faster shutter speed to freeze motion.
APERTURES
Use Av mode to control how wide-to-narrow apertures in your lenses affect exposures
See how a narrow aperture compared to wide captures sharper scenes
Your at-a-glance guide to aperture scales and what settings mean
Altering the aperture is one of your most potent weapons, but this simple control can lead to confusion. The aperture used can create varied, seemingly contradictory, effects. Then there is the number scale in the wrong order…
To simplify things, just think of the aperture as an opening that can be varied in size to control the amount of light reaching the camera sensor. Used in conjunction with shutter speed (the length of time the sensor is exposed to light), the aperture enables you to match the exposure to the brightness of the scene. The wider the aperture, the more light that is let in – helping you to compensate for darker conditions, or enabling you to use a faster shutter speed.
The aperture isn’t in your camera; it’s inside the lens. As Canon EOS DSLR and EOS R mirrorless lenses are removeable, the range of aperture settings varies on your lens. Expensive lenses tend to have significantly wider maximum apertures than budget zooms – eg f/1.2 or f/2.8 compared to f/4 or f/5.6.
What might frustrate those new to photography is the f-stop scale used for the size of each ape
