Does shutter speed affect flash exposure when using high-speed sync (HSS)?
Asked 3/20/2017
3 views
2 answers
0
I understand that below a camera’s X-sync speed, shutter speed mainly changes ambient exposure while aperture affects both ambient light and flash exposure. Does that change when a flash is used in high-speed sync (HSS)? In HSS mode, does increasing shutter speed also reduce the flash exposure?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
6
Is this true also when the flash is used in High Speed sync mode? Or does in this case the shutterspeed affect the flash light too?
Shutter speed has some effect with HSS, but for different reasons. With high speed sync, the flash fires many times as the slit between the first and second shutter curtains move across the sensor. The higher the shutter speed, the smaller the slit, and that may require the flash to fire more often in order to create an even exposure. The flash unit has only a fixed amount of energy, so the more times it fires, the less intense each pop must be.
Originally by user4262. Source · Licensed CC BY-SA 4.0
user4262
9y ago
0
Generated from our catalog & community — verify before relying on it.
Yes. In HSS, shutter speed affects flash exposure as well as ambient exposure.
Below the camera’s X-sync speed, a normal flash burst is much shorter than the time the shutter is fully open, so changing shutter speed mainly changes ambient light, not the flash exposure.
In HSS, the shutter curtains form a moving slit across the sensor, and the flash pulses repeatedly to act more like a continuous light source while that slit travels. Because of that, faster shutter speeds mean each part of the sensor is exposed to the HSS flash for less time, so flash exposure drops as shutter speed increases.
In practice, if you go from 1/1000 s to 1/2000 s, you lose about 1 stop of HSS flash exposure, similar to continuous light. HSS also spreads the flash’s limited energy over many pulses, so effective flash power and range are reduced compared with normal flash mode.
So the usual “shutter only affects ambient, aperture affects flash” rule no longer fully applies once you are in HSS.
Recommended products
UniqueBot
AI9y ago
Your Answer
Related Questions
How does high-speed sync let a flash work above the camera’s X-sync speed?
Which cameras or flash systems can sync faster than 1/250s?
How does TTL flash behave when the camera is in Manual exposure mode?
How does high-speed sync work, and can it be used in complete darkness?
ND filter vs HSS in daylight: which is better for freezing motion with flash?