Understanding Photography Exposure for DSLR Camera

Sunday, 14 October 2012
Executing with all your Efforts to Capture Light :
Photography is the art of recording light. In order to record light you need to know how to tell your camera how much light to record. Understanding Photography Exposure allows you to give correct instructions to your camera. After all, your camera is just a tool, you are the artist.

There are several items that a photographer uses to control light.

* Shutter Speed * Aperture
* Film Speed * Light Meter

Once you understand what each of these items are, it is time to pull them together to create a properly exposed image. It does bear noting that "properly exposed" refers to the exposure the photographer intended. Sometimes the photographer wants to underexpose and image or overexpose it. Proper exposure depends on the intentions of the photographer.

Proper exposure is created by using various combinations of film speed, shutter speed, and aperture. The photographer then checks the light meter to confirm that these combinations will result in the desired light reaching the film or sensor.

Film speed is almost always the first factor that is determined. With film cameras, the film speed is determined by what film you use. In a digital camera, the camera or photographer chooses a film speed equivalent to use in a given situation. The chosen film speed tells the light meter how much light the film requires to create an image.

After a film speed is chosen, the photographer considers the subject and environment of the photograph in order to determine if depth of field (controlled by aperture) or motion control (controlled by shutter speed) is more important to the image. Occasionally there are subjects where both motion control and depth of field are equally important, or the dominant concern can change quickly.

Is Motion Control(MC) or Depth of Field (DOF) More Important?

 * Landscapes - DOF
* Sports - MC * Posed Portraits - DOF
* Nature Photography - DOF & MC
* Photojournalism - DOF & MC
* Architecture - DOF

Once a photographer knows which factor they feel is most important, they set that factor first. For example, a photographer wishes to take a photograph of a meadow with mountains in the background. The photographer wants a large depth of field so aperture is the most important factor in that case. The photographer then sets a small aperture(large depth of field) using the F-Stop guides on his/her camera. After setting the aperture, the photographer looks at the light meter reading and either increases or decreases the shutter speed to move the light meter needle into the center of the scale.

If this shutter speed is below the focal length of the camera lens or below 1/60th of a second, the photographer must do one of two things:

* Reconsider the setting combination
* Use a tripod (or other support) to steady the camera

In cases where the shutter speed is the most important factor, the photographer's choices are further limited. For example, a photographer wanting to photograph a car race sets shutter speed first. Then aperture is set in accordance with the light meter reading. Sometimes there is not enough light available to gain a proper exposure with the desired shutter speed at any aperture.

In this case, the photographer has the following options:

* Reconsider the setting combination
* Use a higher film speed

The bottom line in setting exposure combinations is to know what setting to change in order to use another setting that you "must" have for the image you wish to capture. There is no set right or wrong combination for any image. Every time you take an image the lighting/subject situation changes slightly and setting changes are required to compensate for those changes. You may be able to shoot football images with settings of 400 ISO, f8, 1/250 second on one day and the next day (due to uniform color or cloudy skies) you must shoot with 800 ISO, f4.5, 1/90 second. Use your light meter to know when your settings allow enough light to enter the camera to capture an image.