Lisa here, we own this book, definitely the best book on flash photography Tom & I have seen
Sync About It…or Thinking About Syncing
One of the most important concepts in flash photography is sync speed. This is the fastest shutter speed that your camera can use with normal flash. For most DSLRs, the sync speed is 1/250″. Your camera’s sync speed may be faster or slower — so check your user manual if you don’t know.
Why can’t I use flash at any shutter speed I want? This is a fair question. It has to do with the design of your camera’s shutter. If you use a DSLR or an old-school 35mm film camera, your shutter mechanism has two curtains in front of the sensor/film plane. During the exposure, the 1st/front curtain opens and then the 2nd/rear curtain closes. The difference in timing between the movement of the two curtains is your shutter speed.
At many shutter speeds, the 1st-curtain will completely clear the sensor before the 2nd-curtain begins to close. If your flash fires at any of these speeds, the entire sensor will see the flash — which is what you normally need to make a flash photo. Your sync speed is the fastest shutter speed at which the 1st-curtain completely clears the sensor before the 2nd-curtain begins to move.
At faster shutter speeds, the 2nd-curtain begins to close before the 1st-curtain is completely open. The shutter literally becomes a slit between the curtains that moves across the sensor. So, there is no point at which the flash can illuminate the entire sensor.
High-Speed Sync is a special flash mode that changes the way your Speedlite fires. Rather than fire one big pulse of light, HSS turns the Speedlite into a machine-gun of light that fires an insanely-fast series of pulses. Essentially the Speedlite becomes a continuous light source for a very brief period of time. The downside is that HSS consumes a ton of power. So, your Speedlite in HSS is 2.5 stops dimmer than it is in normal mode. There are loads of reasons to use HSS. Click here for the many articles I’ve written on HSS.
For more details on sync speed and flash photography in general, check out Syl Arena's book Speedliter’s Handbook.
No comments:
Post a Comment