It is the relationship between ISO, Aperture and Shutter Speed – how all these elements work together – that forms the underlying basis of photography. Only when you understand how these different elements work together in making an exposure; will you be able to take full and manual control of your camera. With a solid understanding of exposure; will also come a mountain of creative options and will set you worlds apart from the normal point-and-shooter.
Painting with light
The word photography literally means to “paint with light”. Light is as important to photography as water is to the ocean. Without adequate light your camera cannot see and capture a clear image. It is important to choose accu-rate camera settings to photograph a scene or subject, as you are taking various light options into account.Most of the time, we may use the sun as our main light source. However, in the absence of adequate natural light we may also use artificial light, like flash, to capture images.
What is Exposure?
An exposure takes place when light enters through the aperture or lens opening and through the shutter curtains and then strike the sensor (film) of the camera. It is simple. The larger the aperture, the more light enters the camera. In this case the shutter may remain open for only a small period as ample light is allowed through. If the aperture is wide open and the shutter doors stay open for only a fraction too long, too much light would strike the camera’s sensor and the scene would be overexposed or too bright. The opposite is also true; your image will be underexposed if the aperture is set too small and the shutter remains open for a short period. Properly exposed images are always the result of the right combination of shutter speed and how wide the aperture opens.
Aperture & Shutter Speed / Overexposure & Underexposure
Overexposure takes place if too much light is allowed through the lens opening and the shutter remains open for too long; resulting in excessive amounts of light striking the camera’s sensor. Underexposure takes place when there is not enough light allowed through the aperture and the shutter shuts down the available light too quickly.
ISO Speed
Then there is also the matter of ISO speed. ISO refers to the film or camera sensor’s sensitivity to light. The brighter the scene, the lower you can set the camera’s sensitivity or ISO (e.g. ISO 50 – 100 – 200). Darker scenes need a higher ISO (e.g. ISO 400 - 800 – 1600 – 3200) to ensure that the film or sensor make most of the poor light.
Your camera’s light meter will assist you with your exposures and most of the time, make correct decisions on how long to expose a certain scene or picture. Modern day digital cameras offer a wide range of features that can assist you in making decisions; there is everything from Auto ISO speed, auto shooting modes, exposure bracketing and many more tools. Most importantly, you also have an LCD screen on which you can check your exposure. However, even the best camera’s light meters are sometimes fooled. Issues like backlighting and high contrast scenes are not always correctly interpreted and your camera’s auto settings will certainly make mistakes under difficult circumstances. If you truly want to shoot accurately and creatively you have to set some of these elements yourself.
This is what makes photography difficult. One will need to understand how these various elements work together to ensure perfect exposures. If you get to grips with how these elements work together, then you will be able to make informed decisions on how to correctly expose your images. You may find then, that photography is not difficult at all.
Click here for our more in-depth discussion of ISO speed and Noise..
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