Exposure – Metering

Understanding how your camera measures light is essential for obtaining the exposure you want (which isn’t always what the camera gives). This means understanding metering (and Exposure Compensation – covered in the next post). If you passed the test in Preview 2 then your understanding is adequate. For everyone else, here are four links that may help (in addition to the two videos from Preview 1).

  1. Simplest/shortest – a glossary of 4 metering terms
  2. A 4-minute video –  basic with examples
  3. A 5-minute video – demonstrates what happened with the B&W poster board examples of Preview 2. If you failed the test this is the video to watch.
  4. The most detailed – (and technical; probably more than you need)

Your camera’s metering method defines what information in the scene is used to calculate the exposure. Check your camera’s user manual to find which methods are available and how to switch among them. You will probably have all three methods described in the 1st link above (since in taking this course you’re using a D-SLR). Once you know what metering is available on your camera, you need to try it.
Suggested exercises –
1. Shoot a series of images like the following (click to enlarge) –

Each image was made with identical exposure settings. The metering used was Matrix (or Evaluative). The shots differ only in the distance to the back wall (and/or the focal length). This series illustrates several things –

  • If a scene’s dynamic range is too great for the camera’s sensor, something will be lost – either shadows, highlights or both.
  • Depending on what, in the scene, is most important changing metering mode (and or exposure compensation) may help.

2. For each location in your series, shoot a shot using each of your metering modes (left to right: matrix, center, spot) to get something like –

You can see that the difference in exposure from one metering mode to the next varies greatly from scene to scene. One of the most pronounced is the close-up in the bottom row. Matrix gives us a silhouette which is probably not what we wanted. Look at the left & right images in the bottom row for a graphic example of the difference between metering modes.
For a real-life example of spot metering showing what I envisioned (and not a bird silhouette that I’d have gotten otherwise); click to enlarge. This Red-Winged Blackbird was on top of a small tree with a bright sunlit sky for a background. Impossible to get the subject and background both properly exposed.

Made 4-5 years ago when I was just beginning. For a long time I kept trying shots like this (dark subject against a bright background) – with my meter mode stuck on matrix – and wondered why the subject’s detail was lost (but the background looked great). Finally it dawned on me – use the spot meter! I placed the spot near the bird’s eye (and the resulting image was the very first where the eye wasn’t totally lost in the rest of the black – to say nothing of the feather detail).

PS – Although the above examples tell a discouraging story when the dynamic range of a scene is too large for a camera’s sensor, all is not lost. The image below shows what is possible – just not possible by making a single exposure. I’ll discuss how to accomplish this in the wrap-up session on exposure. For now, compare this with the top row (of the group of twelve images) –

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