All language subtitles for 1_Inverse Square Law made Simple

Now we get to talk about something
that's a little on the technical side,

but I think it's important.

And

it is the inverse square law as it
applies to lighting.

Now, if you're like me, you've probably
avoided the inverse square law.

Maybe in class you learned a little bit
about that.

I did not.

I was in the finars program in
photography,

and so I think the term was out there.

Maybe

I had

a class that emphasized or

required that I learned it.

I never learned it.

I remember it was a mathematical
equation.

So I avoided it at all cost.

You may be like me, I think that

probably two thirds of all
photographers don't really know the

infer square law as the term, but
really don't know what it's all about.

I decided

revisit them for square law, even
though we use it every time we take a

picture, because, just like gravity, we
don't have to know

exactly everything about gravity.

But it applies to us every day.

Just like the inverse square law.

When I photograph,

use a light, the light Falls off.

I know it Falls off.

I

maybe do a lot of guesswork to

that something's going to happen.

If I move a light backwards.

Or forwards or whatever.

So after photographing forty years, I
think I have a little bit of, I thought

I had a little bit of an idea of the
fall off and how that applied to

controlling my light.

So what I did was I took the inverse
square law, went back and looked at the

definition and looked at a few YouTube
of people that were explaining it.

Most of them were very technical,

and of course, applying

the inverse square law with a
mathematical

formula.

And maybe

you heard someone, or saw someone, or
maybe you are someone who took

and used a string that had knots on it
that explained a little bit about where

the inverse square law would say.

If you wanted to darken your background
by one stop, you could take a string.

I don't know, I've heard people do
that.

I've never done it, so

that that helps a little bit if you're
not mathematically inclined

and more of a visual person.

But I even took it, I think, a step
further.

And what I decided to do was to apply
the inverse square law as and look at

it from a visual perspective

and see, how is it that I can

apply that to my photography, my
strobes, my lighting

and will it give me a tool or some
insight to help me down the road?

Well, it turns out that

I was really surprised at

what I discovered.

So I want to take you through that
journey.

I have not done this in the master
class that I did, the joelgrams

academy, under my lighting.

This is all brand new for you guys.

And so I always want to learn something
new, and I hope you do too.

And so let's take a look.

Let's take a swing at it and see what
we come up with.

So

let's take a look at.

This is more of what you would find,

a mathematical

and a bunch of fractions and percentages

and things like that.

So if I look at this, I go,

well, there is a gray scale.

I'm not sure if I added that or not.

I grabbed this

data.

I think I had that.

I made that background gray.

Great transition.

But

you have a light stand,

and then you have, let's go, say,
intensity of light equals one over the

distance squared.

So

what does that mean to me?

Nothing.

Now, some of you are very, very smart
and understand math.

You may go, joah, that's so simple.

But, and you look at the little graph
over here on the right hand side that

with each doubling, I think it would be
the double squaring, the distance.

You get one time, four times, eight
times, will I be, say, time six times?

I don't know what it is.

Yeah, anyways, there's this

fall off

of the light,

and you can plot that out
mathematically.

So since that doesn't apply to me,

I will not

apply.

I won't do that.

If I had to, maybe,

and you put a gun into my head, I
might.

it scares me, and I go, I don't.

That's too much for me.

So what I want to do is look at it
visually.

So here's the question I have.

Can I predict what the value of light

will be as it Falls off behind my
subject, to my background?

So

let's just say, that's a scenario I use
every day.

I have a subject,

I have a background.

Maybe it's not a sweep, or a canvas, or
a Muslim or something, or a wall.

It could be just a couch and an
interior.

So I strobe my subject

and say, the couch is five feet behind
the subject.

Well, is that light that I'm strobing
the subject with?

Will it actually end up

creating a value onto that couch?

Yes, it will.

How much?

I don't know.

So is it possible to plot that out.

It is without a mathematical equation,
I believe it is.

I can look at it and

have what I call a visual cheat sheet
sort of speak in my head.

Or I've got a way.

I can also

maybe have a chart on my phone that can
easily tell me what that value will be

on that couch, or that wall, or that
backdrop, or

whatever it is behind my subject.

So if I move my light away from my
subject, what does it do?

If I move my light toward my subject?

What does that do?

So we're going to learn that.

And it's really actually kind of fun.

And now that I've gone through this, I
thought, wow, I should have done this

2030 years ago, well, at any rate.

So that first question is, do I have
the ability to control

the light

to a point where I can

end up with an in result that I want,
or my client

wants?

Now here's an example

of a photograph that I did for b
cilotto.

It was an ad campaign.

And the reason I'm showing this is
because

I applied the invers square law, not
really knowing it, but in my head, I

had a basic understanding of how light
works.

And I pulled off this shot.

And now that I've learned the invers
square law.

I like,

I applied that to that

photoshoot.

Didn't even know it.

Well, I mean,

I understood by, but now that I have
gone through the invers square, lo I

go, ah,

it's so easy for me to plot this now.

So here's what happened.

Generally, this was my studio pasaden.

That was not a very big studio.

Obviously, this is a composite.

I shot that background

at a casino,

and then was able to shoot this in a
studio, knocked it out, dropped it in.

So, but

the problem that I had was that when I
did my edgy lighting, my two edge

lights, I have one overhead light,

the edge light, when it was close to my
subject, it would light, say, this guy

with a hat, it would light him
perfectly.

And then that light would cast over to,
well, let's just go through the other

way.

It might be better.

So let's go with the guy at the very
back.

So I have an edge light over there.

I get the exposure onside of his cheek.

But

the light that hit the guy in the hat
was

almost pure black.

I mean, I never did.

I didn't get much light to him.

So it looked a little weird.

It didn't look natural

I wasn't getting the light, like on the
girl, the second girl, there wasn't a

whole lot of light on her face.

And so if I increased the power, then
he would be blown out, and then I'd get

her good exposure on her.

And so I was kind of fiddling around a
little bit.

And there's one thing that I do not
want to do when I'm doing a commercial

shoot is fiddle

fumble, whatever you want to call it.

I want to be able to, like that, solve
a problem.

So,

but I realized something.

As

the art director said, no, we need to
have this light, evenly lit,

edgy, but even lit.

I thought, well, i'll back my light up.

So we know that, in the rule of thumb,
is the bigger, the sources relationship

the subject, the software light,

if I back my light up, it's going to be
harsher.

So I had a 26

to 48 soft box,

which is a pretty good soft box,

back it up, it starts getting harsher,
which can be good or bad.

But in this case, it got to where it
was getting too harsh.

So what I did was I took

a

four by five, I guess it would be four
by 54

feet by five feet.

The biggest excel the biggest

box that west Scott makes.

And I put that about eight to ten feet
from my subject, on both sides.

Then what happened was,

I got the exposure correct for the
first guy over here on the camera

camera, right.

His left side of his stuff's shoulder.

Then it was a more of an even throw to
my other subjects.

So once you understand the universal
law, you go,

that makes all this sense in the world.

But at the time, I kind of just

took a guess at it.

It worked because I don't normally
shoot,

or I had never really shot a scenario
where I had to spread my light out

across people.

And so, and from that moment on, I
remembered that.

And we did another scenario with this
four couple.

Well, actually we used two of them,

and we had them sitting at a table.

And then there was,

there's a term for it, but it's like in
a bar, you have this high back,

leather, pleated,

cushioned back, with a cushion, a seat.

And that was pure black.

But when I first set up, I set up a
five foot octo.

I lit the subjects perfectly,

and then the back, which was black, but
it was still kind of shiny, it was

overlit.

So my art director first looked at, I
looked at it.

We went, hmm, it doesn't look like a
nightclub or

a nightclub or a darker environment
evening

out on that town evening look.

I immediately took my

24 inch beauty dish, brought it in
close.

And then my light on the background
fell off very quickly.

So I understood that at that time.

But I still did not realize

how valuable the inverse square law
would be for me to plot

exactly the value that I wanted on that
background.

that's why I think the invers square
law can be very profitable

and learning or solving problems in the
field.

So

here we have

a subject with a gray background behind
her.

Just so actually it's a white
background.

Sorry, white background turning to a
light gray.

And so if I back the back or take her
away from the background,

and same distance the light to her
subject, pull both them back,

that background will get darker.

If I bring it toward the background and
get light.

We know that that's pretty simple.

So I've done that for years.

I understand.

That

here's another one where I

can plot the exact gray that's behind
her.

If I understand the grand for square
law, I can do it

almost without

fail.

In this case, I had to move the
background, and it was on a roller,

I say roller.

That was a studio here in avadel, I
think this was in Pasadena.

So I would have had to move her and the
light away from the background.

But in my other studio actually had

eight by twelve foot

roller that I could move the background
easily

and to get the exact value you want.

So that was done visually.

Trial Nair, snap, click, snap, click.

Then look and see what the background
looks like.

So,

and here's a case where

that,

I guess it was like a sheer kind of

curtain material, or whatever,

that's right up against her.

So my light, her it's white

material.

It turns white.

It's right up against her, so that

I would know.

Here's a situation where I'm shooting a
fifty gray background.

Two, add a texture later,

he's up against it.

It's touching his back.

Therefore I get an exact fifty gray
background right behind him.

If I pull him away or push the
background away, that gray gets darker,

makes sense.

Here we have the wall tapering.

So

it's actually a really good visual of
what inverse square law does.

The light Falls off as it goes back.

Here's another fifty percent gray,

I want that background

to be fifty percent gray,

whether it's a white,

which is backed up enough to be gray,
or a piece of gray that's right up

against her.

So I think you see where I'm going.

Here

there's another wedge wall.

So I've been using it now here's a
situation where I have a white sweep,

and I want that

whole sweep white.

So if I took a soft box and put it
right up, or a reedy dish, whatever,

even though, say a soft box that's
eight feet wide, and put it five feet

from her, that background, that sweep,
would have some gray value in it.

But in this case, I know, and I from
practice, that if I take my light

twenty feet back or 28 feet back, it
simulates sunlight

and the throw

on the

sweep, the white sweep, is going to be
white in front of her, white behind

the inverse square lot, which I didn't
really know, but I knew from practice

I could get that.

So now I know it even more, and i'll
explain so here in a minute.

So here's some more examples.

That was a cross light.

So cross light

up one I'm going to show you.

So here's my soft box, which is
actually an octabox a seven foot octo,

and it's just out of frame, so it's
maybe four feet from her.

Now

we have a fall off.

I have the Rembrandt triangle.

I've been teaching you guys that we're
going to cover that.

Also.

Maybe this is, I'm not sure where this
inverse square law lesson will be in

the one light master class, but we're
covering that a little bit too in this

session.

But

the cheek on her left side

is getting some value of light, but
there's a fall off.

Now it's only

that far

from one cheek to the other,

so it's not a very drastic fall off.

But her arm, the shoulder, is going to
be, let's say,

from the face to the shoulder, that's
about that far,

so that's going to be darker on the
shoulder than it is

on the

shoulder.

Toward the light, it's going to be
lighter than the shoulder

from the light.

Now it is being blocked because of her
body.

But let's just, say, I was to angle her
perfectly,

you would have a tapered amount of fall
off because the light is so close.

Now the next slide is a situation where
I took 27 footers,

backed it up about ten feet out,

910 feet, somewhere, on there.

And the rembrand triangle is still
there.

even of the lit of her across, the body
is going to be

more

equalized.

So again, she's not perfectly angled.

But if I put a white card

and ran it, a piece of foam gore ran it
along.

So the light hit,

it would be

pretty much equal

from the front of the white card to the
back of the white card.

A little teeny fall off, but in the
case of the slide before, there would

be a much Greater gradient.

So when you are photographing a
Rembrandt crosslight, you can keep that

as a consideration.

Do I want the light evenly

distributed across the subject, with
very little gradation of from one

shoulder to the other?

Or do I want it very dramatic, really
bright at the top, and then

it Falls off really quickly?

That's how far your light is away from
your subject.

Now, because

I had the light

ten feet, I needed two big seven photos
to give it the ultrasoft look.

Here's another case where I've got the
light 28 feet back, she's laying on a

piece, white

paper.

And then I got a big piece of two big
pieces of foam core.

So four by eight times two that the
light's bouncing in and coming back

into her.

And so what happened is

the forehead, or say, the blond hair,
or the forehead, is lit with an

exposure.

And as it goes down, let's say,

for some reason, she had her arm

on her stomach, that would be almost
the exact same value of light on her forehead.

But if I had a really close light to
her, the forehead would be lit.

If I got the exposure correctly of
that, then her body would fall off very

quickly into darkness, and her hand
would be a lot darker.

So

knowing that that's applying the invers
square law to

the overall

look that I want.

And the further my light goes back from
my subject, the smoother, or the

more even less evenly lit

the subject will be

from point a to point b.

So I want to show all that in a matter,
but I'm just going through here.

So

here we have the zone system square
scale.

And the reason why I went and picked to
the zone system Scales, because it's a

visual.

And I learned the zone system anzel
atoms the vysm.

And so zone one is pure black.

Zone tens peer white, you have these
gradient steps in between.

And so zone v would be a dead center
and that,

of course, is fifty gray.

So with that knowledge I've had that, I
thought, ok, how can I apply the

inverse square law to a visual plotted
out with zones?

So let's do that.

Let's see how this works.

So I'm hoping that, I'm hoping that

this will make sense to you, and I'm
going to go through it.

And

like I said, I just kind of put this
together.

I'm hoping that I explain this
correctly.

Because sometimes when I do a lesson,
if I do it twenty times, I get a lot

better at teaching it than the first
time out.

So you are the first time out.

So I'm hoping, I get this out
correctly.

So if I have a light source that's two
feet from my subjects, my subject,

and

I, let's just say, I put a piece of
white foam core behind my subject.

And let's just say, for giggles,

I have an f eleven aperture, which I
don't normally do want to do a

portrait.

But let's just say, I do because I want
to plot out some f stops for you.

That white wall, if I get the exposure
on her face

to be f eleven, the white wall behind
is going to be f eleven.

There's a little bit of a depth
distance, but not much.

It might be just a tad under f eleven,

or say,

brighter, no, it would be under underf
eleven, but it's pretty turn close,

because just right up against her.

So let's just say, that's my base.

So my base exposure,

f eleven,

is on my subject and on the wall, or
piece of foam core, right behind her.

So that's at zero feet.

That's my zero mark.

My light is set at a two feet mark

from the subject.

Ok, so let's see what happens when I
take out or move that white

back to two feet.

Well,

something happens.

It's kind of interesting.

The first jump there is a two stop
difference.

So from fleven to 562

stops different.

And so it's going to be

from

peer white, two stops down, which will
be a zone 88

in value.

And the rgb

216, that is your Photoshop,

plotting your Photoshop gray.

So you can do that.

If you know Photoshop,

you can, maybe I put that in there,
because

that's one way of seeing it in
Photoshop as an rgb 216.

So let's go and see what happens if I
go 24 feet.

So four feet is going to be a three
stop difference, a zone seven

and it's going to be f four.

So we go to eight feet,

and that's going to be a zone, a four
stop difference, zone six.

So now we go to

sixteen feet.

That would be a five stop difference at
2 point o.

So now we have a zone five.

So in a scenario where I have a white
wall,

if I want to get his own five out of my
background, I've got to get it up about

sixteen feet back to get true through

five stop

difference.

And so

we're going to have a cheat sheet in a
minute here.

But I just want to show you the most
important thing is, when I move my

light from two feet to four feet, how
it all changes.

So a pretty drastic turn fall off.

And if you kept plotting that out, you
could see it to go to peer black.

I don't need to do that right here,
because, well, my screen's only so big, right?

I could make this smaller.

But anyways, here we have

my 12345

positions of that white foam core, and
watching how the value changes as it

goes backwards.

So if you went,

let's say you took that background,

one foot

would be one stop because the two feet
was too stop different.

So if you say, I only want one foot
that's just one stop difference.

Just back at up one feet.

And you can go in between here if you
wanted to say you wanted a zone five

and a half or something.

so let's take a look at

four feet.

So let's see, we're going to take our
light four feet from my subject,

and let's see how now

that scale of

the zone system changes.

This is important to understand.

So my first wall

is going to be a zone ten at 11.

And so what happens at two feet now?

Well, at two feet, if your light source
is

four feet, doubling what I had before
from your subject, then your two feet

marker is only a one stop.

So it's a lighter,

it's going to be

twice as bright as

the

same position

with

two feet.

Now right now I'm showing just a bare
hood, right?

So you say, well, what happens if you
put a soft box on their octobox?

Same thing?

We're not plotting the harshness of the
light.

We're plotting the

fall off of the light.

So you could have a

six foot

or seven foot octo or a bare head.

It doesn't matter.

It would make it softer if you had a
six foot or a seven foot octo.

But we're not again not plotting the
softness.

what is a four feet?

Give us

four feet is zone eight.

So two stops.

Eight feet, again, is going to be three
stops.

And we go to sixteen feet,

which will be a zone six.

So before it was a zone five at sixteen
feet.

So it's lighter.

So what am I learning so far?

If I back my light up,

the

distance between the subject and
sixteen feet is going to be lighter.

Or the value, the value of my white
wall, is going to be lighter.

At sixteen feet, it'll be lighter.

At eight feet will be lighter all the
way across.

As a general throw it's getting
lighter.

So let's look at all of them together.

Now some of you may say, Joel on board
with this?

I don't know.

I'm just giving you this.

I think we're going to apply it here in
a minute.

Hopefully it'll be a little more
interesting for you.

So here's our

pieces of foam, course, whatever you
want to call them, applotted out it's a

lighter throw.

And we're going to show it in one big
expanse in a minute.

So let's go to eight feet

and see what happens.

So I have my wall.

Right behind

my base is f.

Eleven

at two feet, what happens?

Well,

it's only a half stop difference at two
feet.

So at two feet, it was two stops
difference.

At eight feet it's only a half a stop

lighter.

So as we go down our

scale,

one stop is going to be four feet.

It'll be three stops, two stops at
eight feet,

and three stops at

sixteen feet.

We plot it all out together.

There they are.

It's a lighter set of

zones.

The further I take my light from my
subject,

the

lighter gets as it

throws across my scene.

So let's talk about the light.

This is kind of an interesting thought.

So if I have the sun, which is for 94.5

million Miles away,

I have someone stand in front of that,

and I've a white

wall, white piece of foam core.

If I back it up, what happens to that
white?

Nothing?

Because the Rick show is so small.

So this is an interesting thing.

If you have your sun as your source,

and you have a white wall, you can back
your model away from that white wall,

and you keep taking pictures.

And as white, as just stays white the
whole time,

because the sun is so far.

So how would you get

the sun

to be a zone?

Let's, say, 82

stops.

We'll find that out in a minute.

You've got to go into what's another
planet, over a couple planets over,

to have your

background

that's not happening.

But what I'm saying is that the sun's
so far away that's why you have no

change in your background.

So if let's just plot this out, if I
started out with

zone 550,

gray background.

So you say, how do I get that
background really dark?

Well, start out,

I have, usually,

I carry a white sweep, a gray sweep and
a black sweep.

you're a photographer.

You should always have at least those
three

rolls of paper, or the westcot x drop.

I have the same thing.

I have white, gray and black.

So I put my gray up

at two feet.

Back it's going to be one stop.

At a four feet, two feet it'll be two
stops,

which will be zone

three.

But at four feet let's just, say, at
four feet

here's how I can plot it out.

So I know that once I get my cheat
sheet, that at eight feet is going to

spread a little bit more, but at two
feet it's going to be really drastic.

So zone one will be actually eight feet
back, pure black.

So at two feet i'll have

zone two will be at four feet.

So it's a huge fall off.

So

you want dramatic, you want that person
to pop off the back,

start out with a

darker value background, and then back
it up a little bit, and it'll fall off

really quick.

All right, keep going here.

I hope you're still with me.

Here we have

just a scale, like a wall.

So what would happen if I just looked
at a squall, instead of just these

slots of

foam core?

So here we have two feet.

That's kind of what that wall, as it
tapers down, would look like.

Ok?

And then if I have four feet here, what
it looks like, spreading out

eight feet

and sixteen feet, will give us a

barely, any transition going down a
little bit.

So at 32 feet,

barely, any transition,

you know, 100 feet out, you know, I can
see the transition.

So

let's go to the zone five.

Starting with zone five.

Look how quickly it Falls off

to black.

And

here's our cheat seat, a cheat sheet,

what I would do, and I think I'm going
to try to, like,

post this, i'll create this into a pdf,

and then you'll have this cheat sheet.

So let's look at a chart by looking at
our value and f stops.

So you say, Joel, I think, an f stops.

So if I want to stop

darker, change to my background,

and my subject is

two feet from, or my light is two feet
from my subject,

I know that to get a two stop

darker background, I go to two feet.

So this, as you can memorize, pretty
easy,

match whatever distance you have.

If you have a light, three future from
your subject it'll be two stops

darker,

three feet from the back of your
subject,

if it's eight feet, 16 and sixty feet.

So there we go, four on earth and

no,

945

million Miles away.

To get a two stop darker

background,

you have to get your background

behind your subject,

equal, 4945

million Miles away.

So with that,

the reason why I kept that in the red
is if I memorize that as my cheat

sheet, or my baseline, amount

that's my baseline,

and I set up a subject and I go, I just
want two stops darker background.

So let's say I have a bunch of flowers

on this wall, and I want the flower
just darken a little bit.

And I go, ok,

I'm going to use my twenty four's
beauty dish,

my beauty dish.

I want to put it 24 inches from my
subject to get a two stop darker value

on those flowers.

I'm going to take and have her step
away two feet from the background.

Two stop difference.

If it's a one stop difference, is one
feat.

If it's going to be, if I want a three
stop difference, it's going to be four feet.

If I'm too,

if I have my beauty dish two feet from
my subject,

you see where I'm going here?

Once I understand that, I can say, or
my art director says to me,

we're in a kitchen, I'm shooting this
lady she's baking a cake, and I want to

see the appliances in the background,
but not

over lit.

But I want some value.

Let's say, the art director says, want
just one stop

difference?

Well, then I have to go.

And let's say, if

I take my light, fore feet from my
subjects

and she's standing two feet from

the appliances behind her, then i'll
get a one stop difference.

If he says I want a two stop
difference, I've got to move my light

into two feet.

Don't have a choice.

Now, I might make a decision on what
modify I'd put on there that's a choice.

But

as I move my back up, my light, back
up, the background gets lighter to the

subject value.

So

here's my cheat sheet, and that

stops.

So let's go

and do it in a little bit differently.

This is by distance.

So I can say

I have a light source, two feet I want.

I look at my background and is two feet
behind that.

I know it's a two stop difference.

I look at my background, I measure it
as four feet behind.

I know it's a three stop.

So I have a little stars in red across
here.

That's what I want to look at is my
base.

I look down here, my two stop, two
stop, two stops, two stops.

And then once I learn it as a two stop

baseline, then I can calculate each
direction a little bit

still.

Maybe I got to go to my

cheat sheet on occasion.

But it's pretty easy

to now calculate

what

is going to happen in my background as I

start setting up my shoot.

How are we doing?

That's it?

I think that's my last slide on this
soul.

Maybe this will take a little bit of
you in the studio, and you might take a

subject and a white and a gray
background,

and just play a little bit and see what
happens.

So

you set your beauty dish up, or
whatever, metaphor you have put it at

two feet

and then put your white wall two feet
behind, take a picture and say, ah,

that's a beautiful

let's, say, it's a white wall.

It'll be two stops

from pure white, which makes it a light
grey.

You go, that's beautiful, but you say,
hey, I want a little darker gray.

We've got to back it up,

and you can plot it.

So I hope I know this is a little bit
longer.

I hope

this makes sense to you, and

it gives you a little bit of an insight
to the invers square law, something

I've avoided for forty years.

And

we're good times.

It's nice to have this visual.

Let's, say, forty years ago, I didn't
have a keynote presentation

possibility.

And that be someone on a chalkboard
with.

And that was the easiest way to teach,
was through a mathematical equation.

And I think that's why we're in great
times, is I can now, as an instructor

that does not like math, I can go and
create a visual for you to help you

understand something that in the past
was taught mathematically.

I hope this

gives you a little bit of insight.

So we'll

put it to good news