As promised this week we are going to start our discussion on light. The first thing you need to know is that your camera cannot record the same range of light that your eyes can see. As you look around whatever environment you are in you will likely see a whole range of tones from the brightest brights to the darkest darks. This range from bright to dark is called dynamic range. Our eyes are capable of seeing a dynamic range of about 24 stops! So for instance, you can make out the detail here on your relatively bright computer screen and at the same time see the detail in a heavily shadowed area of your room. Your
camera’s sensor is capable of recording about half the dynamic range your eyes can see, or about 10 to 14 stops. You should feel very fortunate back in the days of slide film we only had a dynamic range of about 5 stops!
What this means is that if you are looking at a scene with a lot of dynamic range (more than 10-14 stops) it might look good to your eye but make lousy a picture. Because your camera will not be able to record all of the dynamic range, so you will either loose the detail in the highlights or in the shadows. You can see when this happens by looking at your histogram. If you are off the scale on both the left side and the right side there is too much range. Generally when I am faced with this situation I wait for a cloud or different, softer light. If that is not an option I will expose for the highlights and let the shadows block up.
Another option if you are faced with a scene that has more range than your camera can record is to create a high dynamic range (HDR) composite image. This is when you create a series of images at different exposures to record all of the range and then use special software to combine them in the computer, using the highlights from one image the mid-tones from a couple of others and the shadow detail from yet another. One of the advancements camera manufactures are working on is creating sensors that are able to record a greater dynamic range.
Good Luck and Good Light!
Steve
Image: Grizzly Bear, Yellowstone National Park