Exposure: Understanding the Basic Elements of Photography   Leave a comment

When I started out with photography, I had the hardest time grasping the key elements to arrive at the correct exposure. Back then, I only had 24 shots in my camera and I didn’t get to see the results of my shots until after the film had been developed. I felt that one would need serious determination, as well as deep pockets, to advance in photography. With the advent of digital photography, I started to appreciate these key elements and manipulate each one to my own advantage. For those of you who’s just starting to delve into the fascinating world of photography, wondering why some of your pictures are too dark or too bright, please read on.

Proper Exposure

Proper exposure is the technical term of taking a photo with just the right amount of light. It is neither underexposed (too dark) or overexposed (washed out). There are three factors in your camera that will affect exposure and all three are interrelated. These are:

  • ISO Speed
  • Aperture
  • Shutter Speed

The relationship of these three factors is what’s known as the “Exposure Triangle”, each factor is directly affected by the other two. Here is a brief explanation on what these factors are and how they affect each other.

ISO Speed

ISO speed, or simply ISO, is the value which denotes how sensitive the sensor is to light. The higher the number, the more sensitive the sensor is. ISO is affected by the aperture and shutter speed in such as way that a low ISO (less sensitive to light) can be compensated with a larger aperture opening and/or a slower shutter speed.  Note that with digital sensors, higher ISO values produce digital noise in photos.


Aperture is the opening in the lens that allows light to come through when a photo is being taken. Its value is denoted by the symbol f/ followed by a number. Take note that the number is inversely correlated to the size of the opening, meaning, smaller numbers indicate larger openings and vice versa. Aperture allows you to control the depth-of-field in a photo. Small aperture openings produce a deeper depth-of-field while large openings have shallower depth-of-field. Aperture is affected by ISO and shutter speed in the following manner; a large aperture opening can be compensated with a fast shutter speed or a lower ISO.

Shutter Speed

Shutter speed denotes how long the aperture is kept open to allow light into the sensor. It is measured in seconds or fractions of seconds. Shutter speed allows you to control the motion blur in a photo. Faster shutter speeds freeze the action while slower shutter speeds tend to blur motion. Shutter speed is affected by aperture and ISO in the following way; slower shutter speeds can be compensated by a large aperture opening or a higher ISO.

The Bucket Analogy

Exposure is best represented by using the analogy of filling a bucket with water from the tap. The size of the bucket represents the ISO, the aperture is represented by the tap, and the shutter speed is represented by how long you keep the tap open. A full bucket of water represents a proper exposure. In order to fill the bucket, you can turn the tap wide open (larger aperture) to fill it up quickly (faster shutter speed), or open the tap slightly (smaller aperture) to fill it up slowly (slower shutter speed).

Knowing how these three factors affect each other allows you to be more creative with your shots. When one factor is constrained, you can use the other two to compensate for it.

Happy shooting!


Posted October 13, 2011 by Alex in Photography

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