Speedlight Notes

Speedlights

Speedlight Basics

  • The power output varies across different brands and models.
  • Versatility depends on ample power and the ability to reduce output when needed.
  • Key output determines the f-stop ranges usable for exposures with flash.

Speedlight Modes: Manual vs. TTL

  • Most speedlights offer constant output (manual) or variable output (TTL/eTTL).
Mounting Options
  • Hot shoe mounting is common.
  • Flash brackets raise the flash above the camera to reduce red-eye effect and harsh shadows.
  • Raising the flash helps avoid downward shadows behind the subject.
  • When using a bracket, a radio transmitter/trigger or a hot shoe cord is needed to fire the flash.
TTL (Through-The-Lens) Mode
  • Light is measured at the sensor after passing through the lens.
  • Camera and speedlight coordinate to determine flash output.
  • The camera measures reflected light from the subject and directs the speedlight accordingly.
  • TTL provides flexibility, especially when subject distance varies.
  • Downside: photographer doesn't know the exact flash output for each exposure.
  • Factors like composition, zoom, and background impact flash output.
Manual Mode
  • Optimal for full control and consistent flash output.
  • Delivers a consistent amount of light, regardless of ambient exposure, crop, focal length, or environmental elements.

Preparing Speedlight for Manual Use

  • Many speedlights have tracking controls that adjust output based on the lens's focal length.
  • The zoom head focuses or spreads light according to the lens's angle of view.
  • Focusing light at longer focal lengths increases effective flash output.
  • Spreading light at wider focal lengths decreases effective flash output.
Zoom Head Functionality
  • Telephoto lens: Concentrated light, smaller coverage area, brighter effective output.
  • Wide-angle lens: Wider coverage angle, light spreads, less effective output.
Disabling Zoom Head Tracking for Manual Mode
  • Disable zoom head tracking by setting zoom to Manual Zoom (MZoom).
  • Select a fixed flash coverage position.
  • Benefits:
    • Speedlight no longer tracks focal length changes.
    • Provides consistent output.
Exposure Prediction

  • Consistent output enables prediction of exposure based on flash-to-subject distance.

  • Examples:

    • At 1 foot distance: f/11
    • At 2 feet distance: f/5.6 (2-stop reduction)
    • At 4 feet distance: f/2.8 (4-stop reduction)
    • At 0.5 feet distance: f/5.6 (2-stop increase)
Inverse Square Law
  • Minor exposure adjustments can be made by slightly changing the light's distance from the subject.
  • Moving the light closer increases exposure; moving it further decreases exposure.

On-Camera Speedlight

  • Convenient but generally produces harsh and flat lighting due to the small light source and direct frontal illumination.
  • Harsh Lighting: Due to small light source
  • Flat Lighting: Light always strikes the subject directly from the front.
Situational Use
  • Suitable for event photography and photojournalism.
  • TTL (or eTTL) is useful in these scenarios with varying camera-to-subject distances and zoom lenses.