How Diffusion Gels Are Used in Film Making

Hi, this is Mike from the Substream.com. And this is another episode in the film lab of
Hell’s Gels.

Last week we talked about Indie Gels which are like the basic gels. They are like the
starter gel and you use them when you want to change the intensity of a beam of light,
without changing the color of the lighter, without changing the shape of the beam of
light.

Today, we are going to talk about another basic type of gel which is Diffusion. Diffusion
doesn’t change the color of light generally speaking although there are some colored
diffusion gels and they only reduce the amount of light or the intensity of it as a side
effect of what they are intended to change which is the shape of the beam of light that’s
passing though it. Now, given that it is called Diffusion, I am going to give you two
guesses, send me an email what diffusion does to that shape of beam of light?

So, thank you for your E-mails. And yes—diffusion does make the light. There is a
couple of different types of Diffusion made by companies like Rosco and Lee. There is
enough that back I’d say eight of their Swatch Book. This is Lee Filter’s Swatch book.
He’s dedicated to different types of diffusion because they make stuff that does different
things, they make stuff that is fireproof or flame retardant or they make stuff that is tough
enough that you’d actually saw it to a giant big frame thing.

And it make stuff that somehow magically doesn’t make any noise when wind blows on
it. So, you can put it on a giant screen above some actors outside and not have to go all
day long when wind blows across it but basic stuff unsurprisingly is called just Diffusion.
And it comes in different fractions. There is 16th light diffusion which we don’t have
because it is expensive and it doesn’t actually do very much. There is eight light diffusion
which we don’t have although we probably should. And then there is quarter light
diffusion. Are you seeing a pattern here?

And does this to our friend Optimus, there is unsurprisingly half light diffusion, basically
double the other. And does this to our friend and in full light diffusion which is Lee
Filter’s number 216, called 216 on set a lot so we can note. That is full white diffusion
and this is what it does to Optimus. So, the closer you get too full white diffusions, the
more the diffusion diffuses the light. And what is actually doing is making it less ordered
and less focused and less coherent. So, what happens at the edge of the beam is that
shadows that it cast on object when you are lighting it with diffusion become less
apparent.

It is like the difference between bright sunshine and an overcast day where the light is
diffused by the clouds and scattered and bounced around in a bunch of different
directions. So, there is much less shadows under folded diffusion or in the overcast sky
than there is under a bear mob or flaming gas giant in space which is the sun.

So, let’s look at it what different types of diffusion do to our friend Optimus and the
shadow that the diffusion creates or doesn’t create. So, this is Lee Filter’s 251 which
quarter light diffusion. This is quarter, compared to full white diffusion that is full, where
did the shadow go? So, what diffusion actually does is it disorders the beams of light, it
makes some less coherent and less focused and less organized. So, the shadows are
lessened and this is really handy because it turns out that when you shine a bear bulb on
unattractive people like myself that have lines in their face and blemishes, those little
shadows that are created make the person looked even uglier.

But when you put diffusion up, the light is softer the shadow are less intense and I go
from looking like really a swamp monster to looking more of just a regular know average
ugly dude. Less hideous, more plain, less of a swamp beast, more of an unfortunate
genetic accident which is very handy.

So, when you are lighting people or things, make sure you’ve always got at least some
half light diffusion in your kit. Remember, it is like Indie if you want to double the
amount of diffusion you can just pull the sheet up and then it is like you had full
diffusion. Check back later on when we talk about other cool gels.