Hi everybody welcome to another episode
of Exploring Photography right here on
AdoramaTV.
I'm Mark Wallace and in
today's episode we're getting really
technical - specifically about flash duration.
A flash duration really impacts
how motion is frozen in a studio
environment, in fact if you do things
right a studio strobe will freeze motion
much much better than a really fast
shutter speed.
You can get motion to be
frozen in 1/10,000th or 1/20,000th of a
second, I mean really
crystal BAM clear...
However not all studio
strobes are created equal,
and even if you have a fancy studio
strobe not all power settings give you the
same flash duration, and so we're gonna
dive into that with some really fancy gear.
I've got a lab setup here, so we're gonna do
some theoretical stuff, and then we're
going to bring in a fantastic model, and
put all this stuff into practical terms,
and so you can see how all of the techno
mumbo-jumbo translates into real life
shooting.
So the first thing I need to do,
is show you the lab and everything we
have setup right here.
So let's do that right now.
On the left hand side here I
have several different studio strobes
from different eras, and different
technologies, so I've got a Profoto B2,
I've got a godox, I have a newer Speedotron head,
and an older Speedotron, and
the Speedotron's are plugged into this
very old pack here, and that way we can
compare some newer technologies and some
older technologies.
We're going to be firing all four of these
heads into a light meter,
now this is a very nice light meter.
This is a Sekonic 858 D U,
and so what this allows me to do is
measure the specific time... the duration
of the flash, and to record that I've got
an Osmo Action setup here to record
this screen, and I've made sure to mount
that low enough so that the measurement
is not impacted by the little recorder
that we're using to record all of our
results.
Before we start metering we
first need to understand some terms,
and how flash duration is measured.
So let me put up a little graph here.
On one axis I have the power setting of the
flash from zero, meaning absolutely
nothing, up to ten, which is full power.
On the other axis I have the time,
so from 0 meaning no time is passed,
to the very end, which shows us how
much time has passed.
Now when a flash fires, the
power of the flash goes from 0 very
rapidly, up to full power 10.
Now some flashes do that really quickly,
some flashes sort of just creep up,
they're a little bit slower and then the power
decreases from full power all the way
down to 0.
Now depending on the flash
that decrease from full power down to
0 can take shorter amount of time,
or a longer amount of time,
normally specifications for flash duration is
measured with a specification called t5,
now that means that it's the time that
the flash is at 50% power or greater, so
how long the flash is at half power or
more, and so that gives us the T5 value,
and that's what most manufacturers will
show you for their flash duration times.
However there is a small problem with
the T5 value, and that is if you have a
very slow flash duration, there's still a
lot of light that's bumping out of that
head, that can still show some motion, so
a better measurement of flash duration
is called T1.
Now what T1 measures, is the power of the
flash from 10% and greater, and so as
soon as the flash hits 10% all the way
to the peak, all the way down to where it
falls below, that is considered a true
total flash duration, and so what we will
be measuring today with our meter is
both T5, the manufacturers specification
and T1, a more realistic view of what a
flash duration is.
All right, we're gonna start doing our
measurements.
Now I need to introduce you to Sam,
this is his studio, and we're stealing some of his
gear, some of his older equipment and
your space, thank you so much for letting
us do.
And he's gonna be helping me trigger
these flashes.
So what we're going to do
here is, we're going to measure the flash
duration specifically at the T5 value to
begin with, and we're going to show you a
chart that shows each of these different
flashes, the ah, how the flash maps out over
time and power, and the meter is going to
show us a readout of milliseconds, and a
fraction of a second, and also it'll show
us our f-stop value.
So how bright it is, and how fast it is,
in two different ways,
and then we'll also see a graph.
It's really pretty cool,
so we're going to start with our oldest,
slowest, technology.
This is a Speedotron head, we're going
to start everything at full power to
begin with, so tell me when you're ready
Sam, alright, Sam is ready go ahead and
fire that - POW...
That is a lot of light we
can see that this is f/28, that's a lot of
power, but it's 4.13
milliseconds or 1/200th of a
second, 1/250th of a second,
so this is not going to be freezing motion.
It's just not a short enough flash duration,
we could have a shutter speed much
faster than 1/250th of a second,
and we can see on the graph here,
that the light goes from zero to max really
quickly, but then it slowly fades out,
and so even our T5 value is slow, but our
T1 value would be even slower than that.
But let's keep moving down the line,
let's look at a newer head, and so this is again a
Speedotron head, but a newer one I
think this is going to flash when we
change the head out, okay yep,
it turns it off, that flashes, some of the old
technology is really fun, so now we're
like using a same power pack, but a newer
Speedotron head, remember this is
4.13 milliseconds, let's look and see what
the newer head does, again
at full power, so go ahead and fire that,
so now we're looking at 3.14,
so it's a little bit faster, our
power outputs about the same f/25,
this is really punchy, and if we look at our
graph, you can see it's just a little bit
faster to fade out, so our T1 time
would be shorter than our T5 time.
Here all right, now we're gonna go down
to a Godox, so now we're into a new
modern technology again, at full power
and so Sam go ahead, and hit that guy,
okay so this is about 1/5
of a second 1.73 milliseconds, at f/18,
so not as punchy,
but much much quicker,
we can look at our graph here,
and you can see that it is a much
shorter flash duration.
It's much more efficient and
now we're gonna go to a Profoto B2 head,
and so again at full power, so go ahead
and fire that, and we can see that now
we're at 1/12 thousandth of a second,
and so it's not even a millisecond,
so this at f/9, is not as punchy as our
Speedotron, but it's a much shorter flash
duration, this is going to freeze
motion, you can see here that our
duration is much slower.
The, the fade-out is a little bit quicker.
Now, watch what happens though,
look at this graph, you see how this is
fading out a little bit slowly,
if we take our power all the way
down to minimum,
so Sam is going to take this down to
the very lowest power setting now go
ahead and hit that ... now
this is metering at not even f/1, so you
have to be much closer, but look at this,
the shutter speed here, or the flash
duration, we're talking 28 thousandth of
a second around there, roughly, and then
look on this chart here, you can see that
that flash is just a spike, and so this
is really going to freeze motion, because
the light essentially hits the subject
and then it's done, there's no fade-out,
there's nothing to show any motion,
now let's compare that to our very first
flash, so Sam's gonna change out the head
on our Speedotron, we're gonna use
that old head, the very oldest technology,
this should be the very worst result, and
we're going to compare this.
So remember 1/27,800 of a second is
of what our Profoto did,
but not very much power so
now we're gonna do this again, go ahead
and hit that 1,000th of a second,
1,000th of a second, so it is 27
times slower than our new technology, and
you see there is just no spike there, so
the point of all of this is your flash,
depending on the technology that you're
using and the power settings that you're
using, is going to change the flash
duration, they're not all created equal,
and so if you have a flash,
and you wanna freeze motion,
the key here is no matter which flash are
using the lower, the power setting,
the shorter the flash duration,
the more efficient it's going to be,
and the better your motion
is going to be frozen, but to prove that
we have a fantastic model, and we're
going to be showing you the differences
between different power settings,
and how that shows or freezes motion
more or less effectively.
Before we bring in our
model I promised that I would show you
the T1 value, so we're just gonna do the
extremes here, so the very first one
we're going to be doing here is, we are
going to be metering the Speedotron, so
go ahead and fire that Sam.
So that fires full power, and this shows
1/69th of a second, that is horrible, and
so we're looking at the entire T1 value,
and you can see really a true
measurement of the flash duration is
horrible it's 1/16th of a second
essentially, it's not gonna freeze motion,
okay let's pop that down to the lowest
power setting, so we can sort of see what
that's going to be doing, so at the
lowest setting here, all right it's all
refreshed ready to go.
Go ahead and click that,
this is showing again at 270th of a
second, I can't say my numbers right, and
you can see that again that's just not
efficient, so it's three, a little over
three, and 1/2 milliseconds.
That is just not a good it's not a very high quality
flash duration, now we're gonna look at
our Profoto B2 again at full power at
T1, go ahead and fire that,
that shows us 1/400ths of a second is really a
more accurate measurement of the entire
flash duration, so that's still not going
to freeze motion the way we want, and so
what we're gonna do here is, go all the
way to the lowest power setting, now go
ahead and fire that, and that shows us
that we're now at 1/9,000th of a
second, that is motion stopping power, and
you can look and see it's because
there's just a spike in that energy, all
right now let's bring out our model, and
show you this in real life terms, well
now we have Maria here, and she is going
to help us demonstrate how this all fits
together by jumping across our scene,
so come on back here Maria, we have put a
little X on the ground here,
this is not a fancy lighting setup,
we just have our old-fashioned Speedotron
here set to about half power,
because I need to meter this, which I'm
gonna do right now.
Now that meters at f/16, which is the
smallest aperture opening I have on this
lens, so we can't put this to full power
cuz I don't have f/25 on this lens, and
that shows me that the flash duration is
about 1/300ths of a second,
that is not really really a short flash
duration, it's not motion stopping flash
duration, so we're gonna prove that by
having Marina just jump around here, so
Maria get ready we're gonna have you
jump across the scene here.
I'm all focused up alright ready, 1, 2, 3,
go, alright, so when we look at this sort of
funny picture, sorry this is not a great
lighting setup, we could clearly see that
Maria has some blurry hands or feet, or a
little bit blurry, this is not frozen
motion, so what we're gonna do next is
we're gonna switch out our Speedotron
and we're going to bring out our B2,
we're gonna see what the same thing
looks like using a newer flash with
newer technology.
Now we're gonna do the same thing
except for now we have a
Profoto B2, this is set at 70% power and
so we're shortening our flash durations,
so let's have you go to your spot here.
I'm going to meter this really quickly,
and this is metering right at f/5.6, and
it's at 3,200th's of a second,
a little bit faster than that actually,
and so this is really going to be freezing
our motion, so I'm going to hang this
really fast right here, and then are you
ready to jump around.
Ok here we go so on the count of three,
ready, uno, dos,
tres go, perfect, and so now if we look
at this you can clearly see that your
hands and then feet and hair everything
is frozen, and that is what a short flash
duration will do for you.
Well thanks Maria for being a good sport
and jumping around and be a little bit
wacky, but I think that shows us that not
all flashes are created equal, some are
better at freezing motion because of
their shorter flash duration, and even
though those can change based on the
power output, so the lower the power
output this shorter the flash duration,
the better you are to be able to freeze motion.
Well, thanks for joining us, make sure you
follow me on instagram, also I have put a
link to Maria's Instagram in the
description of this video.
So you can see all of her awesome
modelling work.
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again for joining us, and I will see you
again next time.