All language subtitles for 03. Understanding flash power.mp4

Understanding

flash power is absolutely crucial to
our understanding of studio lighting.

So to help us do that, I've recruited
our model stiffany.

I also have an aperture and shutter
speed chart.

We have a camera tethered into the
computer so that we can see the

results.

And you'll also notice that I've put a
cstan at the back here, which you'll

understand what that's for.

Shortly,

before we start, let's get some simple
clarification

about the power

of lamp heads.

So we're going to start our first tests
with this particular lamp head.

And this one is an 800

jewel power.

This one

is a 400 jewel power.

So it sounds like it's a lot lot less
than this one.

Well, actually the difference is half,

400 jewels is half the power of 800
jewels.

And in lighting terms,

half the amount of light

is one stop less.

So by now you should be familiar with
apertures and f stops if you're at that

level of using studio lighting,

and we're going to look at that
relationship

between f stops

and studio light power to clearly
understand it.

But first of all, let's simply look at
this.

So for example, if the correct exposure
was at f eleven.

If we had

the correct exposure at f eleven with
an 800 jewel lamp head at full power,

then on a 400 jewel lamp head, we would
need one stop brighter, because

f eight is allowing twice the amount of
light in.

And a 400 jewel is half the amount of
power of the 800 jaw head.

So

the relationship between one stop
changes either a 200 jaw head of 400

jaw head, 800 jaw head, 1600 jaw head,
is exactly the same as the relationship

between one full f stop jumps.

Now we know that we can change our f
stops and our apertures in smaller

jumps.

We can change them in one third
increments, if necessary.

We can actually change the power on our
flush heads in 110th of an f stop

increments, if we require.

So let's start exploring

the change in power on the lamp heads

and see what it means when we go from
full power to minimum power, and why

having a good range of power is
important.

Now to make sure that our test is
consistent,

I'm going to make sure that the
modeling lamp is off.

You can see at the moment, the modeling
lamp is on.

Now if we leave the modeling lamp on
that is quite a lot of extra light

hitting our model.

Now that extra light can actually
affect the exposure of our flashshot,

because it's additional light to the
flash.

So I'm going to turn the modeling light
off so that the exposures that we're

reading, and the results that we're
seeing are purely the flash only.

So

I'm starting on power 10.

And that is the maximum power that I
can get out of this light.

If, for example, power ten was f sixteen

required on the camera,

then if I drop to power nine, I would
require f eleven.

If I dropped to power eight, I would
require f eight.

If I dropped a power seven, I would
require f 5.6.

Because each drop from ten to nine to
eight to seven to six, on a studio

light, is a one full f stop jump.

So we'd have to adjust the apertures
accordingly.

But I don't know yet exactly what
aperture setting we need four power ten

at this particular distance.

Because also keep in mind that the

power

of a light

is also related to the distance from
the subject.

So as we move a light closer to our
subject, the power of the light will be

stronger.

If we move the light further away, the
power of the light will decrease.

Now, other factors also affect the
power of the light, and that is when we

put different modifiers on.

So if we put a soft box on the light,
or an umbrella, or we bounce the light

off of a different surface, then a lot
of that power will be dispersed into

different directions, and it will
reduce the power.

So for this test, I'm just using a
standard l forty reflector,

and

that's it.

And we'll direct the light

straight at our model, and we'll see
what exposure settings we require.

So first of all,

coming into my camera,

framing up and focusing on my model,

I'm using a shutter speed a 160th of a
second, because that's the

sink speed that will work with this.

The shutter speed doesn't have any real
bearing on the exposure for flash.

But i'll explain a bit more about that
later.

First of all, we're going to set our
aperture.

So I'm going to set my aperture to
start with, to f 22

in this case.

So my starting aperture is f

22.

My lamp is on power ten, which is full
power,

full power on an 800 head.

If I had power ten on this head, which
is a 400 jewel,

that would be equivalent

to power nine on this head,

because this light is one stop less
powerful than that light.

So back to power ten.

No modeling lamp.

Let's take our first shot.

We're using the trigger on top of the
camera to trigger the flash gun,

taking our first picture.

And you can

hear that large outburst of light.

So that picture is now going to come
into

the computer.

And we can see the first result there,

which looks a little bit over exposed.

So that's at f

22,

an aperture of f 22.

And there's the result.

So I'm going to close the aperture down
to f 32,

to one stop.

Less light able to get into the camera,
which will reduce that

exposure.

So let me do that quickly.

So changing the camera now, I'm just
changing it to f 32.

Taking that picture again.

Same power on the studio.

Lamp.

Let's look at the result on screen.

So there we go.

We now have the correct exposure

on

We can see the skin tone seems well.

Exposed.

Is just a single light setup.

Obviously, as we demonstrate more
lighting, examples will be showing you

lots of ways to light a model.

This is the most simple single light
setup.

Now

what's important to notice, here is the
level of detail on this cross bar in

the background.

So remember, we're at f 32,

and we have the correct exposure,

and our depth of field is quite large,
because we can see the model is sharp.

And this object in the background,
which is actually about three

meters behind the model, is also
becoming quite sharp in the picture.

And this is why it's important to have
a large

range of power in your flesh unit, so
that you can control depth of field.

So we're now gradually going to change
the exposure

of the flash and the apertures on the
camera,

reducing depth of field at the same
time.

But before I do that, I'm going to
leave the aperture at f 32,

and I'm going to change the power of
the light just by 110th

of an f stop.

So I'm going to take it from power x to
power 9.9.

So from ten

to 9.9,

take the shot.

Let's take a look at the result.

And there we go.

We can see the difference here's at
power 9.9

and there's at power 199,

power, 199,

power ten.

So that's only 110th of an f stop.

And that's why that difference looks

so subtle, because it is very subtle.

110th of an fstop is a very small
amount as you can see there.

So let's carry on in full f stop.

So at this time, we're going to go from
power ten, where we were here.

I'm going to go to power nine.

So power nine.

Now, when a light goes down in power,

you do need to allow the light the time
to reset its power.

Some flash units require you to
actually dump the power manually out of

it.

But an advanced flash unit like this
one doesn't.

It will rebuild balance itself.

So we've now dropped down from power
ten,

from the exposure on screen now, to
power nine, which is one f stop less.

Let's take that shot,

and let's take a look at the result.

That was power ten.

That's power nine.

So you can see this is one f stop less
of light.

That one was power 99.

There's our power ten shot.

Now there's power nine.

So you can see a whole f stop of light.

Now a whole f stop of light

is actually a reduction, is half the
amount of light.

Remember, an f stop is either half the
amount of light or double the amount of light.

So in light terms, we add the correct
exposure at f 32.

We've dropped the power to power nine.

And now our picture is underexposed.

So we now need to open the aperture by
the equivalent amount by one f.

Stop to f 22 to bring our exposure back
correct again.

So

changing my aperture in my camera

to f 22,

from f 32,

leaving it a power nine.

And we'll now see that the exposure

on this one we'll now be correct.

So we can now see, f 22,

that this exposure is correct for power
nine.

And if we go back, we can see that that
was the exposure at f 32 at power 10.

And you can see that they are very
close.

Now any discrepancy in power where
there's a slight little bit of

difference is not actually down to the
light.

It certainly won't be down to these
lights, because they are very, very

high quality professional lights.

The discrepancy here will be in the
aperture in the camera.

So we're now at f 22, and we have the
correct exposure.

But what happens if we change the light
more dramatically?

If I go, say, four f stops

brighter in aperture

1234,

maybe five, maybe six,

let's go four.

So we're going to go 1234

f stops brighter on the aperture.

That will require us to turn the power
of the light

down four f stops, because we're
letting more light in with that aperture.

So I'm going to change from f 224,

f stops brighter to f 5.6.

So f 22,

open the aperture up to f 5.6,

take the shot.

And it will now be dramatically

overexposed,

because it's going to be four stops
over exposed, as you can see here,

because we doubled the light, we
doubled the light, we doubled the

light, and we doubled it again.

And there's the result, a massively
overexposed

shot.

So we have to turn the light down by
four f stops to match.

So from power nine

to power 8765

that's a four stop reduction

in power.

We let the light rebalance itself take
that shot.

And now we should have the correct
exposure

and voila.

So now we have the correct exposure
because we reduce the power of the light

to match the aperture setting.

And if we go back

and we look, we can see that our
exposure is correct.

But what we'll notice is the difference
in depth of field.

And this is why it's very important to
have a large power range on your flash

unit, because it gives you this Greater
creative control over depth of field.

So here for example.

Now we're shooting at f 5.6.

Before we were shooting at f 32.

Here is the result.

Ah, I believe it was this one at f

32.

And now here is the result at f 5.6.

So our model still looks sharp, but our
background, depth of field has changed dramatically.

And with this particular flash unit, I
can even open the aperture more,

because I'm only at power five.

So I can open up

two more stops, for example, from four
to three.

And we'll try a test shot from 5.6.

Now

open up the

aperture

from four to 28.

And let's have a look at the result.

And there you go.

So now we can see that the depth of
field has even more greatly reduced,

lost focus on her a little bit, which
you can't be quite in focus.

Let me just readjust,

there we go.

She's back in focus.

So let's compare our shot at f 28

at power three,

compared to

function 32

at power ten.

F 2.8,

f 32,

f 2.8

is at power three,

and f

32

is at power ten.

So you can see that huge difference in
change of depth of field.

And interestingly,

I can still go down one more stop.

But unfortunately,

I can open my aperture any more than 28
on this particular lens.

Because 28 is the maximum aperture of
that lens.

But if I was using a different lens,
like one of my 12 lenses, I could open

up another stop further to f two to
reduce depth of field even more, if

required.

So that's one of the reasons why it's
really important to have a great power

range on your flash units, which this
particular flash does very well.

So the next demonstration, and just to
prove the physics of it and the f

stops, is to show you a 400 unit at
power ten, compared to an 800 unit,

800 jewel unit at power x.

So let's go back to f 32 at power ten.

On this light,

let's go back to f 32 on our camera.

Let's take a look at the result.

So we should have

the same exposure.

There we go.

So we flip between the two again, and
you can see the difference

clearly.

So now we're f 32,

we have the correct exposure, and we're
on power ten.

I'm going to change the lamp head

to a 400 jaw unit from this 800 jaw
unit, and we'll see what happens when

we have that at power ten.

If the physics is correct and the lamps
are correct.

We should be required to open up a stop
to f 22 to retain the correct exposure.

Let's turn this one off.

Take it off of this lighting stand that
want to get it in exactly the same

position with the new one.

So let's lift that off of there,

put that lap head on the floor.

And let's take the 400 power lamp head,

move that onto here.

It has the same reflector on it.

So everything should be equal.

Or just need to make sure it is also
pointing directly

our model,

is pointing at our model.

And I'm going to take this up to power
ten.

Now the modeling light has come on, so
I'm going to turn the modeling light off,

so everything is equal.

So

we have power ten on this lamp head.

We had power ten on our last lump head,
but our last lamp head was 800 jewels.

This is 400 jewels.

So it should be one stop less powerful
than our last shot.

Let's take that shot,

and there we go.

We can see the shot on the 400 jaw head

is one stop less powerful than the shot
on the 800 jaw head.

So the physics is exactly right.

The apertures,

the half in the amount of light
doubling them out light is absolutely correct.

So to get the correct exposure on the
400 lamp head, I would now need to

change my aperture from f 32 to f 22 to
get the same exposure.

So whilst the number sounds a
significant difference from 800 to 400,

it actually only relates to a one stop
change.

So you can consider

what type of lighting power you need by
calculating

it in f stops.

So going from an 800 jaw head to a 1600
jaw head, whilst that sounds like a

great change, it's actually only a one
stop increase in power.

However, keep in mind that one stop is
still quite significant.

It's double the amount of light, or
it's half the amount of light.

So to continue,

I'm going to go back to my 800 jaw head
because there's something else I want

to show you in relation to power.

And that is, what do we do if we

get the light power low enough for the
larger aperture that we want to use?

So let me change back to the 800 power
head.

And then I also want to show you a
comparison of the power of one of these heads,

or the 800 head, especially compared to
the power of, say, a speed like flash gun.

I'm going to change lens on my camera,
because, remember,

I could only get

to power three,

f 28.

Now I want to go to a lens that can go
much wider than that.

So I'm going to switch to my 85
millimeter lens, which has a maximum

aperture of f 1.2.

Ok?

So now we have a lens that can open to
a larger aperture.

And remember, we were at f 2.8

before.

So I'm going to shoot

the same

exposure, f 2.8,

and I'm going to change this lamp to
power three,

which is where we were before

when we were shooting f 2.8

on the other lens.

So now we've got a slightly wider angle
lens.

We're at 2.8.

We'll take this shot,

and we should end up with exactly the
correct exposure.

Ok?

So there we have

f 28 on this lens.

You can see it's a wider angle lens.

This an 85 millimeter lens.

I was using a seventy to 200 before.

And we can see the exposures pretty
good.

It looks a little bit brighter than I
remember from the comparison on the

other lens.

But as I said, it's very unlikely that
the flash

power is wrong.

It is clearly the aperture number is
wrong, because we're using the same

amount of flush

power

three.

And we were using power three before.

So there's a slight discrepancy here in
the actual camera aperture settings of

f 2.8

on one lens and f 2.8

on the other.

Now there shouldn't be, but this is
actually quite common in a lot of cameras.

So

anyway, we'll accept that as being the
correct exposure.

So I can now drop that power from three
to the minimum power on this light,

which is power two.

So I'm going to go to power two.

We go that's power, too.

That's the lowest power I can set on
this light.

Now I need to open the aperture

on this camera

by one stop.

So we're going to f two.

Take the picture.

Take a look at the result.

And we can see here

we have

the correct exposure, or this matching
exposure.

See how the depth of field

decreased again, even from 28

to f ii.

Some of the extra exposure that we're
seeing

may be down to ambient light.

And this is partly related to as that
aperture has become very, very large.

It's now starting to pick up some of
the continuous light that we've got.

Around us.

So the lights that we're using to video
this sequence right now, or any

daylight coming in through the window,
is actually starting to get captured as

that aperture opens up.

This is also how the shutter speed can
affect the amount of light.

If we look at the shutter speed range,

when we're talking about flush, we
don't really need to consider the

shutter speed,

because it's only the aperture.

as we lower the shutter speed with
flush photography, then we let in

daylight in addition to the flash.

And that will build the exposure
brighter.

But I'm going to cover that in more
detail later.

So let's go back to our initial problem.

And the problem is that I am now at the
minimum power on this light.

I'm at power too.

It doesn't go down to power one.

If we were using this scorrow pack, for
example,

I could not only go down to power too,
I could go down to power one.

Power 0.98,

I can go down to 0.1.

But this is obviously a much more
expensive, much more professional

system.

It also has the ability to go much,
much higher in power.

This is a 300200

jewel unit compared to 800 jewels that
we have here.

So that has the ability of going two
stops more powerful than the maximum

power on this light.

Anyway,

how do we solve the problem?

Now, if I want to go from f two

down to f 1.4,

let's watch what happens.

If I go to 1.4,

we know

that the picture is going to end up
over exposed.

So I go to 1.4,

take the shot,

and we'll see,

the result

is now a stop

over exposed.

And I can't do anything about it

because I can't reduce the power of the
studio light any more.

All I could do now is choose to move
the studio light further away

to reduce the power.

But there is one little trick that I
can apply, which i'll show you,

and here's the trick.

This is a neutral density filter.

It's a filter that will cut out

extra light.

So in this case, this is a 0.9

filter.

That means it's three stops strength.

It will cut out three stops of light.

Now in this case, I don't actually want
to cut out three stops of light, only

one to cut out about a stop of light.

At the moment we are at f 14.

I'm now going to cut out three stops of
light,

which will be too much.

We look at the result on screen,

and there we go.

This picture is now three stops

underexposed from our previous picture,

and we're at power

too.

But the beauty is that I can actually
now increase the power to compensate

for the fact that the filter is too
dark.

Filters obviously come in different
strengths,

so you could have applied a less strong
filter.

So looking at that result looks like, I
want to go up by about a stop in power.

So I'm now going to take the light up
to power three.

I'm going to take the shot again.

Needs to go up a little bit more,
another stop.

So we're up to power four now.

And there we go.

There's an exposure level that I'm
happy with.

So I've managed to obtain

f 1.4

on my camera.

And by using a filter,

I've been able to increase the power

to get it correct for 14.

Previously we weren't able to obtain an
exposure less than 28,

because the light would only go down to
power two.

Now that is still a massive reduction
in light power.

These particular lights are very good
for a large power range.

But if I wanted to go lower than f 2.8,

where I won't gone to 1.4

by using a filter, I was able to
achieve it.

In fact, I was able to achieve it so
easily, because this is a three stop

filter, I had to actually turn the
power of the light back up again.

Ok,

finally,

on flash power, we're now going to look
at the power of a monoblock studio

lamp, such as this one, compared to an
on camera

speed light.

So on this

stand

all the time

was a light meter, or more importantly,
a flash meter.

Now flash meter

does what it sounds like it would do.

It measures the amount of flesh.

So turning this flash meter on

and just angle that down a little bit
so you can see it,

you can see I've got some Numbers here,

and I can set the iso, the shutter
speed, and then it's showing me an

aperture value.

So when I fire the flash, it will
measure what it thinks is the correct

aperture value.

Now we're going to come to using light
meters and why they might be a good

idea, or why they might not be a good
idea in another section, but for the

purpose of measuring the flash power
accurately right now, and comparing a

monoblock head to a

speed light, or maybe even comparing it
to the more powerful scorrow, pack this

will be useful.

So we'll just pop

the flash meter there, which is where
the studio light was directed.

And let's take a reading.

And I'm going to aim that directly at

the light meter.

I'm going to turn the power on this up
to power ten, which is the maximum

power.

And I'm going to press the test button.

Oh, I haven't activated this yet.

Sorry, let's

activate the light meter.

Push that test button again.

Now let's see what it says.

It is saying

f 32.

Well, actually it says f 22.9.

But if you look at the scale up here,
it says f 32, which is interesting, because

our camera also required f 32

to get the correct exposure.

So this light meter is actually giving
us an accurate reading,

very close reading to what we would
have needed to set in the camera.

So by comparison, how would a speed
light?

Ready?

We've got f 32 or 229

there on that.

One.

Let's see what we get with the speed
light.

So here's a speed light.

I've put it into

manual mode,

so I've got one to one that's full
power.

You can see the zoom is at 28, which
means the spread of light will be quite

wide.

That wouldn't be really fair on this
because the spread of light, although

wide on this, is a little bit more
directional.

So I'm going to change the zoom to
seventy millimeter

on here

to give a more or less

equivalent spread

to

the

studio light,

and then direct the lamp head.

I'm going to turn this off,

and I'm going to put this in the same
position.

I'm just going to activate my light
meter.

Press the test button,

and we have a reading of f 11 and a
half,

11 and a half

compared to f 32.

So we lost

two and a half f stops of power.

So this thing on full power,

was two and a half f stops, less

than our 800 jaw lamp head.

The other reason that these lamp head,
these

speed lights, have disadvantages,

is, obviously, this is battery powered.

It isn't as versatile with the amount
of adapters and umbrellas or soft boxes

or accessories that we can add to our
light.

And those are the most important
things, because we need to control the

light, shape the light and change the
light to give the most

aesthetically pleasing light on our
subjects.

And those are things we'll be covering
later in this,

of course,