HSS – HIGH-SPEED SYNC FLASH – A BEGINNER’S GUIDE
Before I get into the technical aspect of what
HSS is, and how it works, let me tell you WHY
you might need it.
It is an absolutely gorgeous day outside, nice
and bright as is so typical here in the high
desert. The sun is pretty much right overhead,
so you are going to have to use a fill flash to
even out the shadows. You and your model
have selected a perfect spot to shoot, you’ve
metered and found that at ISO 100, and a
shutter speed of 1/200th, your aperture will be
f/9.0 (1/200th is the fastest shutter speed your
5D Mark III can use to properly sync with your
Canon Speedlight).
But the background is just a bit too busy, too
distracting for your taste. What you want is to
somehow narrow the depth of field so that the
model pops, and the background blurs out. The
“normal” solution to that problem would be to
open up the aperture, as wide as it will go…that
should greatly reduce the depth of field. Right?
Absolutely correct! However, when you do
that, you also need to raise the shutter speed
considerably to compensate…well beyond the
sync speed of your Speedlight.
You could add a neutral density filter to cut
down the amount of light entering the lens, that
would allow you to lower the shutter speed and
still keep the aperture wide open…if you have
one with you. Or I suggest, you could select the
High-Speed Sync function on your Speedlight
and shoot at 1/1000th, or even higher! Here’s
how it works.
If you tried to narrow the depth of field by setting
the shutter speed faster than the maximum sync
speed of your camera, you would wind up with a
photo like Image B because the second curtain
has already begun to close when the flash goes
off, cutting off part of your image.
However, in High-Speed Sync Mode, things work
just a bit differently.
Instead of the flash firing a single, full-power
burst of light, it fires smaller, rapid pulses of
light, thereby providing adequate illumination
throughout the entire time the curtains are open.
This allows you to increase the shutter speed to
whatever you need to accommodate the much
wider aperture and give you the narrow depth
of field, as in Image C.
Image A
f/11 @ 1/200th
Normal Flash
Image B
f/2.8 @ 1/2000th
Normal Flash
Image C
f/2.8 @ 1/2000th
Flash w/HSS On
Model: Analesa Maldonado
In very simplistic terms, in "Normal Flash Mode"
when you press the shutter button, the front
curtain inside your camera begins to open. Once
it is completely open, the flash fires and the
rear curtain begins to close. The period of time
the curtains are completely open is dependent
on the shutter speed you have selected, i.e.,
1/200th of a second. Results would be similar to
Image A with a wide depth of field.
HSS is also invaluable when shooting motion
shots against a strong backlight...you need a fast
shutter speed to stop the action, but you also
need a fill flash to illuminate the subject that is
being back lit.
If you haven't
tried
using
HSS, give it a
shot. It could
be just what
you need to
light that photo
perfectly.
Stock Photo