Light is a requirement for all types of photography. It can be manipulated to create mood, and enhanced to change the entire make up of the image. When light has burned the image on to the film/sensor, it is known as an exposure. A photographer can do everything right with the aperture or shutter, but if the right balance isn’t met, the image can be either under exposed (too little light), or over exposed (too much light). The built in light meter on your camera should tell you if an image is properly exposed or over exposed by indicating dots (stops) on a spectrum of +1…i…0…i…1- by adjusting the shutter or aperture on your camera you adjust the settings so the exposure is either exposed properly, under exposed, or over exposed.
Above is an image that was properly exposed, the right Aperture and Shutter combination made the image “properly exposed.” Now look at the same scene, only under exposed.
Note the subtle differences, the sky looks good, but the shadows are really pronounced on the building itself. Now here’s the same scene only over exposed.
In this scene, the Sky has gotten “blown out” which basically means it has so much light that it has lost its colors & textures that the under exposed image had. However the building has lost its shadows and is well lit know, also the grass is more green & vibrant.
There is a relatively new type of photography called High Dynamic Range (HDR) that takes these differences in exposures and uses them to develop brilliant images. The human eye can see more spectrums of light than the sensor on your camera, thats why your picture of the sunset rarely looks like the actual sunset did. The reason HDR photography is so unique is it actually captures a wider range of available light than a normal image, thereby making images that contain more potential.
After this image has been processed using either Photoshop or Photomatix Pro, or what ever your favorite HDR Software is, you can do what’s called Tone Mapping, which is where you get to tweek the light & colors of the image before you do the final processing. The image below is the final HDR edit.