Camera & Craft

Try This at Home

Chapter Six: Controlling the Light

Gray, White and Black All Over

Steps

  1. Grab an 18% Gray Card, 1 a sheet of white printer paper and a sheet of black paper (or black velvet).
  2. Put your camera on a tripod, place the gray card in your scene so it fills the viewfinder and then light it evenly.
  3. Put your camera into Manual exposure mode and use the Spot meter.
  4. Take a reading off the gray card and set up a good normal exposure. Take a photo.
  5. Replace the gray card with the white paper. Again, take a reading and set the camera to give you a normal exposure. Take a photo.
  6. Replace the white paper with the black paper. Again, take a reading and set the camera to give you a normal exposure. Take a photo.
  7. Review and compare all three photos: They should all be roughly the same tone of gray. 2
  8. Be mystified and amazed.

    Explanation

    Our instincts tell us that the camera should have known somehow to capture the walls the way they looked to our eyes—so why did each wall (or sheet of paper) photograph as gray? The answer lies in understanding what reflected light meters are trying to do. First, they measure the light coming from an object (the wall). Second, they’re calibrated to make that object expose as a mid-tone. The assumption is that most things we photograph are primarily made up of mid-tones and that metering for them will result in the correct values—but that isn’t the case.

    When your camera’s meter read the exposure from the gray wall, it exposed the whole thing correctly, because it was one big mid-tone. But black and white walls are distinctly not mid-tones, so when your camera’s meter read them and it did what it was calibrated to do—read the light reflecting from them and photograph them as mid-tones—the results were inaccurate. This occurred because the reflected meter measures light coming from an object, not the light falling onto it.

    When you put your meter into Matrix mode and point it at a real scene, the meter still assumes that everything it’s pointed at is a mid-tone, but its sensor actually looks at the pattern of light and dark areas in the finder and compares it to a database of likely scenarios programmed into the camera, attempting to find the closest match.

    1The 18% gray card is Andy’s favorite old-school gadget. He only uses these particular cards, because they use a certified Munsell mid-tone gray and are stable and color neutral.

    2 A lot of paper isn’t color neutral, especially white paper. There are many tones of white, and often, blue dye is added to them, because it makes the paper look brighter to our eyes. Even black paper might have a color shift in it. You may end up with three different looking gray images that have more to do with color changes than density changes.