1. Seeing the Light (Exposure and White Balance)
Chapter Seven
Seeing the Light (Exposure and White Balance)

2. Why bother with exposure settings?
Built-in light meters evaluate light in the scene, i.e. how much light is there?
The final exposure depends on aperture, shutter speed, and ISO settings.
Automatic exposure settings normally give you “alright” pictures.
Knowing how different settings affect your pictures gives you “good” pictures.

3. How light meters see the light
Light meters see only luminance, not color.
Light meters measure a scene and gives you an “appropriate” exposure setting.

4. What is an “appropriate” exposure setting?
For “darker” scenes, the light meter will suggest more exposure (larger aperture and/or longer shutter time).
For “lighter” scenes, the light meter will suggest less exposure (smaller aperture and/or shorter shutter time).
The result is always an image that is, on average, neither too dark or too light but in the middle—the middle gray.

5. “Average” exposures

6. Metering Modes Matrix (multi-segment, evaluative) Most sophisticated
Divide the scene into a number of zones and measure light on each zone separately; use all measured data to arrive at an exposure setting
Good in most situations
Need adjustments in tricky scenes, e.g. backlit, snow, beach, etc.

7. Metering Modes (cont.) Center-weighted Spot
Emphasize the center portion of the scene
Commonly used for taking portraits
Can be used together with exposure lock for off-centered subjects
Spot
Only emphasize a small “spot”, about 3%, of the scene in determining exposure
Useful for backlit or dark subjects

8. What to meter Tricky scenes: Simple solution:
Large area of dark background behind the light subject
Backlit subjects
Simple solution:
Point your camera to a “middle gray” object in the scene and meter for it
Lock the exposure by half-pressing the shutter
Keep the shutter half-pressed and re-frame your scene
Fully press the shutter

9. Exposure Lock
High-end cameras include a very useful exposure lock button (AE Lock)
Instead of half-pressing the shutter (which also locks the focus), you may focus on a middle-gray subject, press the AE Lock, and then re-frame and refocus.

10. When to Override the Meter
Backlight scenes
Meter for the subject
Fill flash
Exposure compensation
Snow and beach scenes
Reflect too much light; tend to under-expose
Nighttime
Meter tends to suggest more exposure than appropriate.

11. Exposure Compensation
On top of the meter’s suggested exposure settings, you can increase or decrease exposure conveniently by exposure compensation.

12. When to use exposure compensation
Depends on particular light meters
Is the subject too dark or too light compared to the background?
Does the scene reflect a lot of light? E.g. beach
Experience counts
Always experiment

13. Using the Histogram
Shows how pixel-by-pixel tonal values in the image are distributed along the tonal range.

14. Controlling Highlights
The histogram tells if the image contain highlights that exceed the tonal range of the camera.
To avoid, use exposure compensation.

15. Preserving Shadow Detail
Histogram can also help reveal any clipped shadow detail.
To avoid this, use exposure compensation.

16. White Balance Familiarize yourself with all the white balance settings
Use custom white balance when necessary
Using the RAW file format allows you to set white balance during post-processing

17. White Balance Auto Bracketing
On high-end cameras, one can take a picture based on the current white balance setting, and the camera will create two (or more) additional images with slightly different white balance settings (slight warmer, and slight cooler settings).

18. White Balance as a Creative Tool
Adjusting white balance can give your image a different “feel”
WB = Outdoor (daylight)
WB = Indoor (tungsten)