Seeing the Light

In the early days of photography, it was discovered that if you averaged out all the light values in a standard landscape scene, it would tally up to 18% gray. That means when you add up all the bright sky areas, all the darker ground areas and included stuff like trees, structures, shadows, etc., you have the equivalent light value of an 18% gray card. Light meters in all cameras these days are based upon this same 18% value. It sets the camera’s exposure based on this. It reads the light reflected off of whatever you are photographing and then processes this data as if that value was 18% gray, and your camera sets the exposure accordingly. If you are photographing a typical scene like one mentioned before, then the 18% gray value should work. However, if you are photographing a bride wearing all white, that tends to skew the meter reading quite a bit. It will tend to underexpose the image to bring it back to 18% gray. The same happens when you photograph someone in front of a bright window. The meter tries to bring the window in line and unfortunately the person in front of the window is underexposed.

Different camera manufacturers have various metering methods programmed to deal with extreme lighting situations. But none are perfect. Reflected light meters will still give different exposures, for instance, metering two people with black complexions and two with caucasian skin tones. It’s going to try and average both of their skin coloring to 18% gray. So one will be underexposed and one overexposed. If you want consistently more accurate metering, purchase a hand-held meter like a Sekonic model 358. It has two modes of reading the light, reflective and incident. Reflective is similar to the camera’s meter. Light is read after it bounces off the subject.

Using the meter in incident mode is much more accurate. You read the light source at the subject’s position. By this method, the meter is not fooled by skin color, clothing color, background influence, etc. The meter simply reads the volume of light falling on the subject and the image is recorded exactly as it looks. The Sekonic meter I mentioned has a white dome that is used for incident readings. It has two positions. In standard mode, it is full out. It reads 180 degrees at the same time. Not good. The other way is to turn the dome and it recedes into the meter. In this position, it only reads light from one direction. This is the way you want to use it. Then just aim the sensor at the light source, and it won’t be influenced by extraneous light sources like the sky, etc. If you want to improve your photographic images, pick up a light meter that can give you incident readings with a flat sensor or a dome that recedes. Set your camera on manual, and get ready to be amazed at the difference.