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

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.

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.

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.

“Average” exposures

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.

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

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

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.

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.

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

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

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

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

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

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

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).

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