All language subtitles for 11_Defocus,depth-of-field_blur,bokeh,and_spherical_aberration

in this lesson

we're gonna learn about defocus

depth the field blur

Boca and spherical aberration

so here's where we left off

and we're getting really close to

finishing out all of our optical aberrations

so now let's take a look at one of the more common

aberration which is defocus

now defocus is one of those things that's so simple

it barely bears repeating

and that is when we are focusing on a specific

distance from our camera

objects that are further away

and closer will be out of focus

since we're focusing in on this

dessert right here

objects that are further away will begin to defocus

and that is

essentially in any photograph or any footage

now we call this depth of field blur or depth of field

and it's caused uh

partially by how wide your aperture is open

so in most cases

if your aperture is very wide open

say f 2 to f 5.6

you're probably going to get some depth of field blur

however as you close down your aperture

you're going to be extending your depth of field

therefore causing less blur

now there's two more words

we said Boca and sphere collaboration

Boca is the name for these

out of focus shapes that we get inside of our camera

and uh this is a Japanese term defining

how appealing this shape is

so here we can see we have a roughly circular Boca

and it is um

not very interesting

well here in this other photograph

you can see that our Boca is many different sizes

different colors

different shades

different shapes

so on and so forth

uh the Boca also shows you the lens

so here we can see some spherical aberration

or in other words the lens

because it is circular

is not going to be distorting the light 100% correctly

so how does that apply to our depth

the feel blur

or our Boca

well what happens is

either the inside of our Boca gets lighter

and then our edges have a bright ring around them

or the inside is brighter

now physically accurate

or in a perfect system

the inside would be bright and we would have

just a simple Gaussian fall off or just a blur

to the edge

but spherical aberration

often causes these kind of shapes

as well as the chromatic aberration

we can see along the edges of this Boca

now one last look at Boca

showing off some food photography

here we can see an even stronger sphere collaboration

you'll notice the shape in every single piece of Boca

is roughly the same

we have this center here that has a dark ring

uh surrounded by a brighter ring

and inside is a light circle

along with a rainbow

fall off at the bottom of the outer ring

now as you can imagine

this is a complex phenomena

that involves your entire lens

uh to create this effect

so let's jump into nuke

and take a look at one way we can do this

now we're not gonna be able to get as full

featured Boca as we've taken a look at

with our default tools without

an incredible amount of work

so let's take a look at what we can achieve quickly

and then we'll talk briefly about how we

can get that level of detail

so let's actually jump back to the top of our scene

uh remember this

uh no tree is acting as if we are going from the

outside of the lens in

down towards the sensor

which is our final viewer

depth of field is something that happens

outside of our lens

but is affected by our lens

so often placing it inside of our comps is difficult

however what we would like to have to create a

depth of field effect is a foreground

object and a background object separately

separately rendered so that we can have uh a nice

addition of

the foreground over the background

since we are going to be blurring various parts of both

so inside of our foreground

since we do have a 3D render

we have a Z depth pass

now if you wanna add depth of feel to a

real life piece of footage

it's gonna be a much more involved process

usually because there already is some depth to feel

blur available

and creating a depth pass from real footage is time

consuming to say the least

so here if we drop down our channels

we can see we have our Cam Z

now this looks like just a blank or a

full red channel

but if we dial back our viewer

we can see that there actually is data here

and this is just a simple

um depth pass from Maya

so to use this

we can add in a Z blur note

so I'm gonna hit tab and drop in Z blur

and plug this in between

our foreground and our foreground

uh over background merge

let's now take a look at this Z blur node

and let's jump back to our RGBA

of course we have uh

many lessons on this node

as it's a pretty useful node for creating this effect

for now let's just jump into our focal plane setup

and if we take a look at our Camz

we can decide what value we wanna start at

so looking at the red channel

looks like 19 is around where we wanna start focusing

so let's set our focal plane for nineteen

and then we can begin increasing our depth of field

now we do need to set the depth channel

normally nuke defaults to the depth Z

however ours is in a different place

it's in this Cam Z depth

so we'll drop it down to that

that will give us exactly what we're looking for

so here we set the focal plane

and now let's increase the depth of field

because we do not want most of this image to be blurred

so now let's take a look at our result by turning off

our focal plane setup

now this is gonna be a little bit difficult to see

so let's take a look at this

uh in our merge

and we can see a few problems

so the first problem is we have a Halo around our edge

and this is because it's trying to depth the fuel blur

around essentially nothing

so we're gonna need to either extend our

edge out or figure out how to fix this

but uh more worrying is that

our alpha channel is being degraded

and we have this strange Halo

around almost our entire object

and it looks almost like a light wrap

but I'd really like to figure out why this is happening

so let's take a look at the alpha channel

so if we go into our Z blur

and go into the alpha channel

we can see that our alpha falls off very quickly

and to really understand this

we're gonna have to look at our depth channel

so if we go to our Cam Z depth

and take a look

at the R channel

or hit a to get out of our alpha mode

we can see that the

depth of field is around

let's see here

15 to 20 uh

depending on where we are on the edge

now outside of this is zero

and remember

zero is close to the camera

so what's happening is

it is blurring out these pixels

because it thinks everything in front of it

is close to the camera

so therefore

it is blurring out our alpha by quite a lot

so there's a few different ways we can fix this

I'm just gonna go for an shortcut

by adding in the darkest color we have

into our uh

depth field

so that we no longer have that issue of such a big jump

between depth values

so let's go to our depth

and let's pull down our viewer

until we can see

where the darkest value is

inside of our depth pass

and it looks like it's one of these corners

so maybe around

I don't know 37 38

and so now let's take a

constant of that value

so I'm gonna hit tab

type in constant

and just put in a value of 38 oops 38

and now let's merge this with our current depth

so I'm gonna hit the m

key to drop in a merge node

and let me just give us

some room here

and I'll plug this into our constant

now we're gonna wanna merge our constant

with our depth pass

so we're gonna want to

output into our depth pass

so output into Cam Z

now this is just gonna overwrite everything

or it's gonna combine our RGB

and the constant we just created

but instead

in the B channel

I'd like to bring

in the uh Z

so let's go to

our B channels

and let's go to our other

layers Cam Z

so now if we pull this down

we're gonna see

that we have

the constant

in the background

but it's currently being

added to our

current depth of values

and instead

we wanna keep our

current values

and fill in

everywhere else with zero

so to do that

let's grab the

or let's change

the operation to under

which is gonna take the B

alpha channel

and since we

don't have anything

let's plug our

current camera

depth into that channel so again

other channels

Cam Z depth

what we should see

is our original

here and then everything

else is filled in

with this new

constant so again

this is kind of a workaround that

just fills in these

empty pixels with a different value

so now that our

background is

truly further away from

our camera than before

let's take a look

at the result

so if we go to our Z blur

jump back to our RGBA

and take a look

at our alpha channel

you can see that is much cleaner

so now if we go back to

our foreground

we can see these

edges have fixed themselves nicely

so currently

we do not have much of a depth blur

we're really only blurring one pixel

which isn't a lot

so let's pull this size up a bit

and we can see

as we increase this

we are now blurring

any object that is further away from the camera

now I don't want this to be at such a

extreme size

but I pushed it that far to show

you that we still have this issue

and this is because there's

currently a black

outline around

our foreground

if you take a look

we have a single pixel

of black outside

and we do not want that

so let's crop that out

and turn off black outside

so now our edge pixels are completely touching the edge

and if we look at our merge

they are now being blurred nicely

although the blur is still far too strong

so let's pull that back

uh let's maybe give this a nice

I don't know 4

6 uh choose whatever value you want for this shot

again the amount of depth blur is

directly tied to the aperture that you're shooting at

so if you're shooting very wide open

which is honestly unlikely in this bright area

you're gonna have a higher depth of field or

a larger depth size

otherwise you're gonna have a smaller depth size

now we also wanna

uh blur or add this to the background

so let's move our background up a little bit

and let's clone our Z blur node

so control excuse me

Alt K will clone that

and now we don't really have a depth channel

uh for our background

uh but just as we did with our constant we

can add in uh sort of another background

so our biggest value was 37

uh the sky or 38 and the sky is very far away

so let's give this a color value of 3 80

and this is just to make sure that our sky is always

as far away as possible

so I'm gonna hit the m key to merge this in again

and we'll plug the a pipe in

actually instead of a merge

uh we could use a shuffle copy note

we're not really merging anything

so I'm gonna hit tab and shuffle

our constant red value into our Cam Z

which is what that Z blur note is using

okay so let's see here

we want the red channel of our

input to go into the Cam Z

of our output

and now our Z blur is going to blur this

according to that depth

okay great so we've begun to set up our Zeebler

and as we can see here

we've got a little bit of a depth of field effect

now for us to really see the Boca

let's go to a later frame

when our camera has already moved

and we can see one of these highlights

and the shape it's creating

because as you can see here

we do not have a lot of Boca

alright so on one of these later frames

let's zoom in

and take a look at our Z blur

if we zoom in

let's actually increase

the size of this

just so we can see the Boca a little better

there we go

so this highlight is currently creating a

square shaped Boca

which I don't believe any lens has

only 4 aperture blades so that

um that is just

a very simple Gaussian blur shape

now if we want to have a circular Boca

inside of our Z blur node

we can increase the filter shape up to 1

and that's gonna give us this nice

circle however

that is really the

extent we can

affect the Boca shape

inside of our Zeebler note

again this note is not going to give us

the amount of control we need

to create that really fine

really detailed Boca

what this Z blur

note is allowing us to do is it is allowing us to do

a very simple depth of field blur effect

that we can use to

sort of defocus things

that we want

uh that are further away from the camera

as we can see here

so again the Zeebler note is not gonna be able to

get us that really nice Boca

there are quite a few plugins

for nuke the um

Lens Care plugin

the Gen Arts plugin

uh there's a few more that

escaping my

uh memory right now

but they all

are built to create that very expressive

uh very complex

Boca that we

want in our

very short shots however

unless you're really doing a macro

shot or something

that is supposed to be very small

uh you're really not gonna have as much Boca

as we saw in our earlier

photographs

the depth of field is gonna be

slightly smaller

and much more subtle

so that's how we can use

the Z Blur note as

as alongside

a Z Depth pass to

create a nice

depth of field

effect here

inside of nuke