Thursday, December 17, 2009
Deciding what matters (in a picture, exposure wise)
The nicest and sometimes most appealing pictures are taken with great lighting. Every degree of brightness in the scene is reproduced in the picture, nothing is really too dark or too bright to fit. If you look at the histogram, it is a beautiful shape, a mountain pretty much centered with nothing blown out or in total shadow. For example, this picture of a train south of Moosonee shot in 2008.
Usually, if you point your camera at a scene it will do a pretty decent job of coming up with a decent shot. Most cameras have built in software for evaluating a scene and deciding on the settings to use to end up with a decent exposure.
Sometimes what is front of the camera makes it difficult to get a perfect exposure.
All cameras have limited dynamic ranges. This is the range from the brightest to the darkest lighting that can be contained in a picture. I suppose it is a bit like the contrast range statistic advertised with tv sets and monitors. The nasty thing is that human eyes tend to have a better dynamic range than cameras.
When you get a scene that exceeds the dynamic range of your camera you need to decide what matters. Are there relatively dark objects in the scene that you want to show up with detail and colour instead of as dark shadows? Is there something that is really bright and beautiful that you want to show up properly?
The classic example is taking a picture of the rising sun. On a clear day, when the sun is not dimmed by clouds or fog, there is no way you should even be aiming at the sun. So the most memorable sunrise and sunset pictures include lots of clouds or are taken when the sun is not directly visible.
A more reasonable circumstance is when you are taking a picture and the sun is shining towards the camera. If you have a subject facing you, that subject is going to be a shadow if you want things lit by the sun to turn out propertly.