Overview
This lecture explains how flash duration impacts motion blur and exposure in studio photography, providing practical demonstrations and recommendations for controlling flash duration using strobe power and freeze mode.
Understanding Flash Duration
- Flash duration is the length of time the light from a flash is emitted during a shot.
- Exposure time in flash photography depends on both camera shutter speed and the flash duration.
- For fast-moving subjects, a shorter flash duration is needed to avoid motion blur.
Measuring and Adjusting Flash Duration
- Always check the T0.1 value for flash duration on strobe specs, not T0.5, for accurate measurement.
- Lowering flash power results in a faster (shorter) flash duration and less motion blur.
- Each reduction by one stop in strobe power generally halves the motion blur.
Practical Demonstrations
- High strobe power increases motion blur; lowering power progressively reduces it.
- Even at minimum strobe power, some motion blur may remain for very fast subjects.
- Using freeze mode on strobes further shortens flash duration but may shift color temperature toward blue or magenta.
Freeze Mode and Color Considerations
- Freeze mode rapidly dumps power to achieve faster flash duration, affecting color accuracy.
- Always use a white or gray card to correct white balance when using freeze mode.
- Mixing different strobe types or modes can result in mismatched color temperatures.
Additional Tips and Real-World Examples
- Speedlights (on-camera flashes) can provide very fast flash durations due to their low power.
- For maximum sharpness, use the lowest strobe power and freeze mode where possible.
- Stack multiple low-power strobes for more light without sacrificing flash duration.
- Example: Photographing perfume spray—freeze mode yields less motion blur and sharper detail in motion.
Key Terms & Definitions
- Flash Duration — The time interval during which a flash emits light in a single burst.
- T0.1 (tenth-value duration) — The time period during which the brightest 90% of the flash’s light is emitted; more accurate for motion freezing.
- Motion Blur — Visible streaking or softness in a photo caused by subject movement during exposure.
- Freeze Mode — A strobe setting that shortens flash duration for less motion blur, at the cost of color accuracy.
- Strobe Power — The output intensity of a studio flash, adjustable in stops.
Action Items / Next Steps
- Practice adjusting strobe power to observe changes in motion blur.
- Use freeze mode for subjects requiring minimal blur and perform white balancing with a gray card.
- Review your strobe's manual for T0.1 specs and freeze mode features.