How To Understand Your Camera

by William Lulow

One of the best ways to understand your digital camera is to read the manual. I do not mean this facetiously! Digital cameras, even though they try to make the photographic process simpler, are complex tools. They have a great number of automatic features built in to them designed to yield good exposures in almost every kind of lighting situation. You can set your camera’s controls to AUTO and snap away, being assured that most of the time, you will get a fairly well exposed image. The thing you have to ask yourself though, is “Is this what I want?” If the answer is “yes,” then you need not read any further. If you wish to make images however, that are a bit different from the norm say of rainbows, or deep sunsets, then I suggest you read this article.

The Beginning

A camera is essentially a tool for modifying light enough to make a desired image. The lens collects and alters light rays and focuses them on a sensor or piece of film at a spot behind it called the “focal plane.”

You can control the amount of light that hits the focal plane by mastering three major parts of the camera.

  1. The camera’s ISO setting. This tool controls the amount of light entering the camera by setting its sensitivity to light. ISO stands for INTERNATIONAL STANDARDS ORGANIZATION. This is an international group of people who decide what standards the world will use for most items that require numeration of some sort. The lower the number, the less light the camera “sees.” So, an ISO setting of 100 will be less sensitive to light than a setting of 800, say. If you are shooting in a situation where there is very little light, (at night, say), you might need to use a higher ISO number so that the camera can “see” more light. In many cameras equipped with a built-in flash, if you don’t change the ISO number, the flash will automatically pop up to add light to the scene. This would be undesirable in shooting a sunset, for example. So, if you don’t want to use the flash, you would need to increase your ISO setting.
  1. The camera’s shutter speed. This tool controls how fast the camera’s shutter opens and closes. The shutter is usually calibrated in numbers that range from 1 second to 1/1000th of a second or faster. If the shutter is allowed to be open for a 30th of a second or longer, the camera will not be able to stop any action. Most objects will be blurry unless the camera is placed on a tripod or other stabilizing device. Here is an example of an image where the shutter was left open for longer than 1/30th of a second:


The red and white lines are made by cars’ headlights and tail lights. They are blended together because a slow shutter speed was used.

The following image was made with a very fast shutter speed which was able to “stop” the action. Approximately 1/500th of a second:


  1. The Camera’s Aperture: Each lens has a diaphragm which controls how wide the lens opens. This tool is calibrated in what is called F/STOPS. The “F” stands for focal length. I won’t get in to the mathematics associated with each f/stop, but suffice it to say that each major “stop” represents either a halving or doubling of the amount of light reaching the sensor, depending on which way you go. For instance, the widest aperture is usually f/2.8 or f/1.4 or f/3.5 depending on how big the piece of glass used to make the lens is. The larger the glass, the lower the “f/number.” So, an f/1.4 lens is larger than an f/2.8 lens. The larger the lens, the more light it can let in to the camera. We call this a lens’ speed. So, an f/1.4 lens is “faster” than an f/2.8 lens. The larger the f/number, the smaller the lens opening or “aperture” is. So, if the light is very bright, as on a beach or snow, you would need to “stop down” the lens to f/16 or maybe even f/22, to reduce the amount of light reaching the sensor. Conversely, if the light is very dim, you would need to open up the lens to f/2.8 so that the lens can let as much light in as possible.

Here is an illustration of lens apertures:

Lens apertures

These are the main tools you can use to control the amount of light that hits the sensor. There are also other ways of altering the light that hits the sensor. Most digital cameras today have various modes from which to choose that change the quality of light after it hits the sensor. It can be sharper or fuzzier. It can be bluer or redder. It can have a hue (color tint) to it. There are probably another two dozen ways that your digital camera can record a scene. We will leave this for another discussion.