14
High Speed Sync
Focal Plane Shutters & Flash Sync
Modern DSLR cameras use focal plane shutters to achieve speeds up to 1/8000th of a second.
These shutters work fine with electronic flash at or below their sync speed. Sync settings range
from 1/160th to 1/250th of a second depending on make and model. For shutter speeds above
the sync speed, the secondary curtain starts closing the shutter before the front curtain is fully
open. The resulting slit or space between the two curtains paints the sensor with light allowing
very fast shutter speeds. Higher speeds have narrower spaces between the two curtains. At these
high speeds, the frame is never fully open. Photographing with electronic flash at shutter speeds
faster than sync results in a partially exposed frame. The remainder is black. The higher the shutter
speed, the wider the black bar and the thinner the portion of the frame that receives flash will be.
What is High Speed Sync (HSS)?
High Speed Sync allows flash to expose the entire sensor at shutter speeds faster than the camera’s
sync speed—even up to 1/8000th of a second. Higher speeds control ambient light in a photograph.
The higher the shutter setting the darker the ambient becomes. HSS is great for darkening
backgrounds even on sunny days.
This is a representation of the cutting effect made by focal plane shutters at speeds higher than sync with flash.
