Friday, May 22, 2009

A Very Simple in Camera Technique

The image that goes along with this post is a straight shot. (It'll be used as a component of a composite image one of these days.) The branch of the tree wasn't removed from a background to isolate it. The shot was taken along the Blue Ridge Parkway, at a roadside turnout. The turnout was right on the top of a ridgeline with fairly steep valleys on either side. Cloud cover was low enough to be hugging the ridge. The wind that day was coming from the east, where the lower clouds were. You could actually see the clouds race up the hillside and crest over the ridge at a pretty good clip. This branch was on a tree on the east side.

That's the setup. Here's how the image was taken to get the detail and color in the branch. One thing to keep in mind is that cameras, like computers, are dumb as a stump. Either will only react to what you "tell" them. If the exposure was left zeroed out as the meter "read" the scene it would have come out with the cloud being grey and the branch being in silhouette. The meter would have been fooled, wanting to average out the scene to a neutral grey. With as much white as in this scene you need to use the "Exposure Value" (EV) compensation adjustment available in just about all DSLR and some higher end point and shoot cameras. If you're not familiar with this type of situation, the first thought would be to go negative with the EV because the scene is so bright. Actually, you want to go counter intuitive. The meter is trying to make the scene grey. In order to "fool" the meter (actually, to make the meter do what you want) you'll want to go to the plus side of the EV scale. In the case of the branch the EV was increased by two full F stops. What happens is the meter now reads the scene as two F stops above the neutral grey it wants and exposes the scene properly.

The same adjustments need to be made if the scene were 90% dark. The meter still would want to render the overall scene as a neutral grey. To get the rich blacks you'd look for in a night scene you would go the opposite way and take the EV down a couple of F stops to get a correct exposure.

Today's cameras have amazing meters in them. On a nice day (sunny or not) the meter will do an accurate job of setting the proper exposure. You can have the camera on AUTO (don't do it), or P (does that mean professional?? I think not.), or Shutter Priority (know if you looking to freeze motion or show motion), or Aperture Priority (know what sort of Depth of Field you're interested in) and get a decent photograph. When you're faced with something on the fringe is when you have to do the thinking and just let the cameras meter do the mathematics.