The three legs of exposure

I posted previously about the importance of exposure and metering in photography.  Metering is the algorithm that is used to decide how to expose the picture.  The camera then chooses the camera settings to achieve the optimal result based on what the meter tells it to do.  When adjusting exposure, there are three key elements that can be modified.  In another post, I will go into more details on these.

Shutter Speed – This parameter controls how long the sensor (or film) is exposed to light.  The longer the exposure, the more light reaches the sensor and the brighter the image.  However, long exposures bring challenges particularly when photographing items that are not stationary.  This is measured as a fraction and so smaller number are slower shutter speeds.  For example 60 is 1/60th of a second and is slower than 1000 which is 1/1000th of a second.

Aperture – This controls how how much light the lens allows through.  Think of it as a door into a dark room.  A wide open door will allow much light while a cracked door will allow very little.  Like shutter speed, it is measured in fractions and so f4 is a larger lens opening then f11.

ISO – This controls the sensitivity of the sensor.  By changing the ISO, you adjust the sensitivity of the camera’s sensor and can thus take pictures in darker situations without a flash.  Higher ISO’s will lead to more noise in the picture and so there is no free lunch.  ISO is measured in 100’s with the higher the number the greater the sensitivity and the more noise.  Most people shoot their DSLR’s at around 100 – 200 while most point and shoot cameras shoot around 80.

This post only provides the very basics.  I hope to cover each of these topics in greater detail in the future.

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One thought on “The three legs of exposure”

  1. I’ve always had aperature compared to an eye and the pupil. your pupils expand in the dark to allow more light so that you’ll be able to see. Pupils narrow where there is a lot of light so that you can focus on images.

    -in another post, would you explain different types of lenses for a DSLR?

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