Original subtitles

In this chapter we'll be looking at the relationship

of shutter speeds and apertures to flash.

Now there are four segments that I'm going to break this chapter into.

The first one is understanding

flash

sync speeds.

The second one is understanding the relationship of ambient light that's

existing light to our flash, and how we can control that with shutter speeds.

The third

segment is going to be

understanding the relationship of apertures to flash, which basically

control the amount of light coming in, the amount of flashlight coming in, and

how the distance of the flash away can also change the power of the flash, and

obviously changing the power of the flash itself.

And then the 4th section will be understanding first curtain and second

curtain synchronization.

So let's start off with understanding

flash sync speeds.

This is something that confuses

a lot of people, and I understand why it confuses a lot of people.

The simple explanation is that

cameras have a set

flash sync speed listed.

Some cameras it might be 125th

of a second, shutter speed, some cameras it might be 200th of a second.

But people don't really understand why there is a set flash sync speed and

what that actually means.

And then more recently, we've had developments with high speed sync as

well, which has confused things further.

So I'm going to explain

both of those things.

Now.

First of all, to understand flash sink speeds, we need to understand how the

shutter works.

So let's take a look at this old film camera.

This is one of my favorite cameras.

Actually, I used to use.

One of these is the cannon f one.

And if I'm just going to open this up

here, we can see the shutter.

This is the focal plane shutter.

And what I'm going to do let's just wind to the camera.

This used to be for film.

You'll see the shutter

open and closed.

There let's just have another look at that.

There's the shutter

opening and closing.

Ok.

Now, I

showed you on a film camera, because obviously we can see all the way

through it.

Let's have a look on a digital camera, like this, five d, mark, three.

If I take the lens off,

and you can see, there's the mirror in the way,

open the shutter,

and you should be able to see the green colored

ccd or seamos sensor at the back of the camera.

And just see if I can tilt it to the light to get you to

not sure which angle you might be able to pick that up, just if you can see

that sensor in there.

And there's the shutter

opening and closing, where the mirror is lifting up, and then the shutter is

opening and closing.

Now,

the difficult thing for most people to understand

is that

if the flash duration

is very fast, and we know we've already covered flash durations,

we know that the flash duration might be

500th of a second or a 1000th of a second, 2000th of a second.

So if the flash duration is that fast,

then why can't that flash duration be incorporated

into a shutter speed, which is longer?

So for example, why can't we get a 2000th of a second flash duration

inside a 1000th of a second shot speed?

And that's a very good question.

Why are we limited to shutter sync speeds of 125th

of a second or 200th of a second, when the flash duration is actually much,

much faster and should be able to fit within that shutter speed?

Well, there's a good reason.

Let's explain exactly how these focal plane shutters are working.

First of all,

so let's imagine that this green card is a sensor in the camera let's,

imagine this is the digital sensor or the piece of film.

And let's, imagine that this is the focal plane shutter.

So the focal plane shutter will be closed.

And if we're going to run a shutter speed of, say, a 30th of a second, it

would go and open and close

or a quarter of a second,

and it would expose the sensor or the film for that period of time.

So no problem for the flash to fire and expose

the sensor

during that period.

But as the shutter gets faster, it works slightly differently.

It does not work by going

much quicker and much quicker because it cannot mechanically cope with those

speeds.

So what it does is it modifies its operations slightly.

The focal plane shutter

traditionally has two shutter curtains, there called.

And what happens is, as the shutter speed gets faster and faster, it cannot

cope with the speed.

So it changes the method in which it works.

And what it does

is it opens the shutter, the bottom one first,

and then the top one

will come down

behind it

very quickly.

And what that does is it exposes just a

strip

of the sensor

at a time, rather than exposing the whole sensor, which is what happens on

the slower shutter speeds.

Now, because of this, this is a problem for flash synchronization.

Because if you can imagine, when the shutter is fully open, the whole sensor

can be exposed by the burst of flash.

But when the shutter just opens as a small slit, which is what it does on

fast shutter, speeds like a 1000th or 2000th of a second, then only a small

slit, or a scan

of the sensor is actually taking place.

And the problem with that

is, if the flash fires, only a

strip of the sensor is going to be exposed by that flush.

Now, if only a

strip

is going to be exposed by the flash, it is going to result in parts of the

image being blacked out by the actual shutter itself.

And this

is the main problem of flash synchronization.

Speeds with the shutter in your camera.

The problem is not the

flush speed isn't fast enough, it's that the mechanics of the shutter are

changing to this

slit formation,

and the flash is unable to expose the entire image in one exposure because of

the slit.

Now, recently,

camera manufacturers and lighting manufacturers have started to use a

technique called high speed sync.

This works slightly differently.

What this does is allow for a longer flashburst,

that the flashburst

last for the entire

duration of the scan across the image.

So rather than a short burst of flash, the flash is set to actually expose for

longer and more powerfully,

so that the exposure

coincides with the entire scan across the image, across the sensor.

Now this is kind of a fudge work around, if you like, to overcome the

problem of the slit.

Now, on some other cameras, like medium format cameras, it doesn't have this

problem because the shutter is not actually in the camera.

The shutter is in the lens.

And that type of shutter is called a leaf shutter.

And a leaf shutter opens and closes just like an aperture.

And it can do so more quickly.

That means, on medium format cameras, we can actually synchronize at any

shutter speed, right up to the maximum shushota speed, for example, like

2000th of a second on the

medium format household blood page six, for example.

So with medium format cameras, we don't have the problem.

On 35 mile cameras, we can now overcome, overcome, the problem with

high speed sync triggers, which I'm going to show you shortly.

But first of all, let's look at just the current issue of flash sync speeds

with an actual demonstration on our dummy.

So if I take a photograph on the cannon, five d, mark three, with the

standard trigger, and I've got the shutter speed set to 100th of a second,

I'm at f sixteen, I've got a monoblock

studio flashhead here at power eight.

And I'm just going to take a test shot at 100th of a second.

And let's look at the result on the back of the camera.

So here we can see that the

dummy is exposed, or stiffening, as we call it, is exposed correctly.

And the flash power is fine for my aperture setting of f 16.

And we're at 100th of a second.

Now let's see what happens as I gradually

increase that shutter speed.

So I'm now going to change the shutter speed to

160th

of a second

and take the shot.

And there we go.

The result is exactly the same, which is what I'd expect it to be.

So even though we have an increase in the shutter speed, the shutter speed

doesn't really matter in this instance, because it is the flash and the

aperture that are controlling the exposure.

But let's see what happens as I start to increase the shutter speed further.

So this time, this time, I'm going to go to 250th

of a second, which is now beyond the recommended sync speed.

And look what started to happen.

We have a black bar

appear

across our image, and it has blocked out some of the shot.

And this relates to what I was demonstrating before, with the slip

method of recording the image at higher shutter speeds.

So let's increase the shutter speed further.

We go to 640th

of a second now,

and there we go.

So

part of the image, a large part of the image, is obscured.

I'll drop to 400,

there's

another example.

So what you're seeing, what you're seeing there in that image

is the actual

shutter itself

blanking out part of the image.

Because we are now

in the

unacceptable shutter sync speeds.

We're above the recommended sink speed, where the entire sensor can be exposed

in one

go.

Now as I said recently,

like broncolar have also produced a high sync speed connection,

which allows the flash to fire for a longer period

at a higher power output.

To expose the entire sensor, even though it's exposing through a, slit

it's almost like a scan exposure.

So let's see what happens when we change the trigger and put it in high

speed sink mode.

So this is the Hs trigger.

And we've just got a different flash head in one of the Hs compatible ones.

This is the cyros Lithium one, which is

compatible with the high speed sync mode.

So I'm just going to turn that on,

turn this on, make sure that the high

speed sync mode is on.

And let's take the picture again.

So I'm going to start off where we were.

I think we're at about 640th

of a second.

Take the picture.

Now it's dramatically overexposed at the moment, because there's too much

flash power.

So I'm going to turn the flash power down and turn it down by a couple of

stops.

Let's take another one.

And there we go.

So now you can see that we have

our

model stiffany there

exposed

with the flash, even with a fast shutter speed.

Now I can increase that shut speed even more.

So I'm going to increase it up to 2000th of a second,

and it's a little bit darker.

And the reason is that the slit would have been

thinner.

And the way that the

shutter is working means that the exposure is less.

So to compensate, i'll now have to put the flash power up

a little bit.

So I'm just going to take that up half

a stop,

take it again.

And there we go.

So we are able to expose

with

faster shutter speeds

that have

Hs enabled triggers and Hs enabled

flashes.

But as I explained,

it is a bit of a work around.

It's still not exposing the whole sensor in one go in the traditional

method, which is what happens when you're working at sync speeds

the recommended sync speed, where the whole

sensor is being exposed

in one take.

Ok, let's move on to our next

segment.

Ok, the next thing I want to look at is the relationship of

shutter speeds

to the ambient exposure.

And what I mean by the ambient exposure is the existing light, that is the

light that is there, that is not your flashburst

that's light, that is just on permanently.

So either the lights in your house, or the sunlight outside, or daylight

coming through your Windows, just existing continuous light.

Now to demonstrate this, I'm going to switch on the

fluorescent studio lights and the ceiling lights so that we have a form of

continuous light that I don't actually like.

And we're going to show you what happens with that.

But let me explain first a little bit about what's going to happen.

Now we know that if we use a sync speed,

shutter speed, that the exposure is made like soap, and the flash can

expose the sensor in one go.

Now generally speaking, our sync speeds of 200th of a second

or 250th on some of the modern digital cameras, may even be 30400th

of a second.

And as I said, on medium format cameras, it can be even faster.

But generally speaking, those sync speeds are sufficiently

fast.

They're fast enough

to cut out the ambient light from getting in and affecting our flash

exposure.

Unless, of course, you're working outdoors in very bright sunlight.

And that's why the high speed sync modes can be useful to overcome that problem.

If you're working with ordinary sync speed modes, as say, generally, they

would be fast enough to cut out the existing light.

But what happens when you start dropping the shutter speed down to longer,

slower, shutter speeds.

So

then a lot of ambient light is getting in, as well as the light from your flush.

And this then changes the overall look of the image and the overall exposure,

especially if you're working outdoors.

But we're going to demonstrate it indoors by turning on the ambient

lights.

We're going to turn on the fluorescent light

and show you what happens as we reduce the shutter speed in combination with

the flash.

Ok?

So I've turned on the fluorescent

lamps

in our studio ceiling.

Now remember from the first chapter,

when we looked at the spectrum of light and the qualities of light, that these

type of lights are not good for photography because they're missing

part of the spectrum.

And what I'm going to do is I'm going to show you the effect that they have now

as I decrease, slow that shutter speed down to longer shutter speeds,

and we start to see some of this nasty light building up on top of our flashlight.

So we'll still be exposing our picture with flashlight.

Remember, the flashburst isn't going to be affected by this, because the

flashburst is very fast.

So as I slow the shutterspeed, we're not going to add any more flash.

We're just going to add

more ambient light.

So let's look at that in practice.

So just going to go back to the original

trigger.

We're not going to do this in high speed sync mode.

I'm going to go back to a conventional sync speed of 160th of a second.

And

we'll start off at, say,

let's take a test shot.

And there we go.

We can see the result there

at f eleven

with the test shot, we're at power 65.

Can you come and see that?

So there's our

result of the flash,

f 11160th

of a second,

and it's exposed

just about right with flash.

Now let's look what happens when I lower that shutter speed.

So I'm going to drop that shutter speed down to a 40th of a second now.

And now

the exposure has got brighter.

And if we compare that to the previous shot, this is the most recent one,

there's the one before.

Now, all of that extra light you're seeing isn't from the flash,

because the flash isn't changing.

The extra light you're seeing now is from the

ambient light.

It's from the existing

continuous light

so as I increase this decrease, this shutterspeed more and drop it even slower.

So this time I'm going to drop it down to 15th of a second.

And there we go.

At a 15th of a second, we can now start to see this sort of yellowy, greeny

build up of light

compared

to our original

flash

exposure.

There was the original flash exposure only.

And then gradually

this got brighter and brighter with the addition of the

fluorescent lamps.

And you'll probably see it.

If I zoom in here, we'll see it on the shoulder.

Let me just zoom in onto the image.

If we take a look at these highlights just here, I'm pretty sure these are

from the fluorescent lights from the studio ceiling.

And if I go back a shot, there you go.

They've disappeared.

So they're not visible there because the shutter speed was too fast.

And then as I decrease the shutter speed, we're starting to see the effect

of the ambient light pouring into the shot.

Now, this is a common mistake with photographers.

When they're working indoors, they allow

ambient light that shouldn't be there to start affecting their picture.

And they think it's actually the flash, and they start adjusting the flesh exposure,

thinking that it was the flash.

And then they end up getting the wrong balance of ambient light with flash c

and not having the nice, clean, pure light that you get from flash.

Now there are many times where you do want to combine ambient exposure with

flash.

For example, there's many outdoor daylight Scenes where the light is pure

and clean, and you want to incorporate some of the daylight ambient in

combination with your flesh.

So in those situations it's perfectly acceptable.

But there are many situations where you might be working with light that

doesn't have a full spectrum, can give a nasty colorcast, and that starts overpowering

your flash because you have your shutter speed set too slow.

So just keep that in mind for future reference.

Ok, let's have a look.

What's next.

So

we looked there at the

effect of lowering the shutter speed, and that lets more ambient light in.

Now what you would have noticed is that it does not affect flash power.

Because the flash power is constant.

It doesn't change.

There is only one thing that changes the flash power, and that's actually

changing the power of the flash itself.

Or actually the other thing is to move the flash further away or closer will

change the effective flash power.

However, we can control the exposure of the flash, not change its power, but we

can control the exposure of the flash by changing the aperture in the lens,

if we adjust the aperture size, we're either letting more light in or

blocking some of that light out.

And that will change the effective power of the flash.

It will change the appearance of the flash because it is stopping some of

the light getting in.

So if we want to control flash exposure,

we really have three ways of doing it.

One, change the aperture setting on the camera.

Two, change the flash power on the flash itself.

And three, move the flash further

or closer from the subject.

So let's explore that a little bit as well.

So I'm going to go back to

the flash sync speed of 165th of a second.

Take a test shot.

We don't have any ambient light now, only the

video lights that we have on.

But those are very clean, pure daylight balance video lights, hmi lights, so

they're absolutely fine.

If we take a look at my test shot,

here is the result on screen.

I want to make it a little bit brighter.

Ok.

So in this instance, I'm going to increase the flush power by half a

stop, from 6.5

to seven.

I'm going to take the shot again.

And now the shot is a little bit brighter than it was.

There's the one before,

and there's the one after.

There's the one before, and there's the one after.

So I've adjusted the exposure

only by changing the flash power.

In that instance,

however, I can

change the effective flash power, or what's visible, or what's recorded, by

changing the aperture.

In the lens,

the aperture is different to the shutter.

If I change the aperture, now, from f eleven

to f eight, i'll go one stop brighter.

I'm letting in one stop more light,

and now the picture is

one stop brighter from what it was.

So now, f eight that's the exposure I'm getting from the flash.

That's what it was at f eleven.

So I'm letting in more flash power,

but I'm also letting in any more ambient as well.

So with the aperture, when we open the aperture, we are, of course, letting

any type of light in, whether it's flash or ambient.

So if I wanted to work at f eight, which, as we can see

here, is one stop over exposed, if I want that to be my desired aperture.

Then i'll need to turn the flash power down one stop

to power six.

And i'll take the shot again, and i'll now arrive back at the correct exposure.

So that's

two methods of adjusting the flash exposure.

The third method is simply the flash to subject distance.

If I now want this shot to be brighter than that,

I could alternatively

move the flash

closer,

take the shot.

Let's just compare the original.

There's the original that we just shot last.

Take the new shot,

and now it's brighter.

Here's the new shot.

There's the old shot.

There's the new shot,

there's the old shot.

Now I haven't changed the flash power.

I just moved it a few feet closer.

And by moving it closer, remember the inverse square law, we are adjusting

the power

if we're moving the flash source closer to our subject.

So those are the three ways that we can control

the effective flash power by actually changing the power, changing the aperture

or changing the distance.

Ok.

So now we're going to look at

first curtain and second curtain, synchronization of the flash.

This is someone sometimes called

rear sink curtain as well.

Let me explain what that means.

Now, if we're doing long exposures,

like a shutter speed of, say, a second,

then we're exposing for quite a long time.

And existing light like this one, which is a continuous light.

This is our video light to hmi light there.

So this is giving continuous light

that will be recorded during the long exposure.

But we can combine that with flash,

but we can choose whether the flash goes off at the

start of the exposure

or at the end of the exposure.

And that has a big difference in bearing on the resulting photograph.

Let me explain why.

So for example, if I was walking along here

on a long, one second exploit exposure,

then my image would be recorded as a trail, as a blur from the continuous

light.

But if we pop a bit of flash in there as well,

i'll be frozen

at the point when the flash went off.

But if I'm walking this way

and the flash goes off at the start of my exposure

pop, then I'm frozen here, and then I'm blurred here will actually look like

I'm walking backwards, even though as walking forwards.

So in those instances, we're better to switch to rear curtain or second

curtain synchronization

and then what that means is that the exposure will start, I will be recorded

with the continuous light, and then just before the shutter closes, the

flash will fire.

Then, and then the trail will be the right direction.

And who better to demonstrate it for us?

Let's get Mr over to do some test shots.

So we'll look at the camera menu.

I'm just going to go into the menu,

and I'm going into external speed, like control

flash function settings.

And in flash function settings, I need to get across to this one

and choose first curtain synchronization,

or second curtain synchronization.

In this instance, to show you the wrong way of doing it, I'm going to go with

first curtain synchronization to start with.

So I'm just going to get Emma to walk across in a straight line now.

And if we look at the result there, you can see she's frozen,

and then there is the blurred

image.

Trail.

You do that again, come a little bit closer this way.

That's it right?

Off you go again.

So there was the flash.

So there she's frozen, sharp,

and then she's blurred.

Slow.

You walk down a little bit this time.

So, and again, a little bit closer.

That's it?

Just stay on that line.

There

ok,

there we go.

So she's frozen,

and then the image trail.

So the image trail looks like it's going the wrong way because the flash

fired at the start of my exposure.

So now I'm going to go into the menu, I'm going to choose external speed like

control, I'm going to choose flash function settings,

and I'm going to change to second curtain synchronization.

And now as Emma walks,

the flash fired at the end of the exposure.

Now we can see the image blur the correct way.

So now we see the blur behind Emma, rather than in front of Emma.

This gives the suggestion that she's walking in the right direction and that

the trail, the blur, is in the right direction.

Let's go again.

And here we go.

There's the trail blur, and then there's Emma frozen at the end of the

exposure.

So a very simple technique often misunderstood, it's called first

curtain or rear curtain, or second curtain synchronization.

And it's whether the flash fires at the start of the shutter opening, or

whether it fires at the end when the shutter is just about to close.