All language subtitles for 10_A_look_at_astigmatism

in this lesson

we're gonna learn about the different types

of astigmatisms we can have in our lens

as well as how to apply it inside of nuke

so as we're moving through the lens again

the light is being bent

distorted and uh sort of blurred in certain ways

and another way that the light can be distorted or

uh aberated or changed is astigmatism

so take a look at a breakdown of astigmatism

and I'm not going to read you the

uh technical document because it is

uh mind numbing

but this is the basic look of astigmatism

we have a point

and again we can imagine this as a bright white light

and it's going through our lens

now it's going through our

lands on essentially two planes

this red plane is the tangental plane

and this blue plane is the sagittal plane

now all this means is that a point of light

horizontally and vertically

can be in focus in different areas

so the horizontal aspect of that light can focus

in front of or behind

the vertical component

now in our case

we're working with circles

so in our case

the circles

can take one of two forms

so I'm gonna jump over to an image from

uh uh website I found in my research

at tooth walker dot org

and here he has very great picture

showing astigmatism as we're gonna see it

and again I'm gonna

provide these references at the end of the course

so you can take a look at these uh wonderful

uh pages talking more about these effects

so here we have a

image with no astigmatism

so it or the

uh radial raise or the sagittal raise

the ones coming out of our circle

are resolving in the exact same plane

or resolving at the exact same point

as our 10 gentle rays

or the rays that are surrounding are going in a circle

in our lens

however if we have a sagittal focus

then some of the rays

or the rays coming out of our center

are going to be blurry or not in focus

and on the other side

we have tangental focus where the rays or the

points of light that are going around our lens

are in focus

excuse me going out of our lens are in focus

but the race

surrounding or circling

our lands are not in focus

now that was a lot of confusing words

and confusing terminology

so let's jump in the nuke

and take a quick look at how we can add this in

and it's actually quite simple

so here we are back in nuke

and let's just add in our directional blur so hit tab

type in der blur

and this directional blur

allows us to do both

uh sagittal

and tangental

in nuke the sagittal focus or

unfocusing where

the rays that are coming out of the center are blurred

is just called a zoom

so just by adding in this directional

blur wrapper

we have added a slight astigmatism

to our image

now you're probably not going to

read that the directional blur

is actually introducing astigmatisms

but that is

essentially what we are doing

by adding a zoom

and one of the things about astigmatisms

that's interesting is that the center is

as with most of these

optical aberrations

the least affected

and we can see that even with our zoom

as long as we put the

blur centre in the correct area here

so this is again

going to be 1280 divided by 2

or our frame divided by two

there we go

so again this is going to affect

the centre less than the outside so

we can add that kind of quick astigmatism using a zoom

now of course

it's easy to blur this far too much and

add an extreme astigmatism

and so we wanna be careful not to do that

but as long as we leave this on a lower value

we're gonna get a nice slight astigmatism in our image

now if we wanna flip to the other type of astigmatism

the tangental astigmatism

all we need to do is change over to a radio blur

and that is going to essentially spin

and blur our pixels around the center point now

the length is gonna change quite heavily between a zoom

and a radial

so we're gonna need to

pull this radial down quite a bit before we

I have a successful astigmatism because again

it's very easy to overdrive this value

as you can see here

so I'm gonna leave this on a much lower blur length

now when we use the directional blur

uh we're gonna have to be careful because

uh doing a radio blur

will introduce some corners if we have a heavy

astigmatism

so if we increase this blur length

you'll notice we begin

uh showing outside of our frame so again

we'll either have to

uh scale up to hide that or crop down

and I'm gonna just

reduce this blur length by quite a bit

again most lenses have a very slight astigmatisms

so they're not gonna be too expressive or too extreme

but we can add this in if we want

so this is going to be our let's see

this is our radio

so this is our tangental

uh stigmatism

which is much easier to say

or much more difficult to say than our radial blur

and we can also add in the sagittal astigmatism

by just dropping in another directional blur

and keeping it on zoom

now both of these

are going to soften our image quite a bit

so you're gonna need to uh

be careful with this and really decide

how much astigmatism you really wanna

add into your image

because again

it is going to soften almost your entire image

and whenever we drop in this directional blur

we will of course need to

correctly set the blur center

okay so that is a quick look

at how we can add astigmatism or astigmatic

distortions into our image here inside of nuke