All language subtitles for 07_Lens_flares-Visible_artifacts,reduced_contrast,and_saturation

in this lesson

we're gonna learn about everyone's favorite topic

lens flares

so even though I'm sure everyone

understands what a lens flare is

I just wanna take a look at a few examples

so whenever there's a very bright

element inside of our shot

there's a high chance that that element will begin

reflecting through our various lens

elements and lead to flaring

so we can see here

we've got some spike flares

we've also got these aperture shapes

uh that are very subtle in this case

now if we take a look at this video here

we can see uh

a much more uh

explicit lens flare

and you just

you can see it looks like there's a 1

2 3 4 5 6 7 bladed aperture on this lens

and as you can see

some of these flares have some very complex

characteristics

as the camera is moving

we're not gonna be able to get into

uh all of these characteristics

as you can see

it's incredibly

uh complex interactions

so how do lens flares come about

well if we take a look at our lens

we can see again

we have our glass elements

and glass and

somethings by nature are reflective and so

what happens is these glass elements are highly treated

highly coated

highly processed to not be reflective at all

because if they are changing the image

then it is not a true picture of what is happening

but for very bright elements

when there's an incredible amount of energy

like with sun or spotlights pointing into our camera

even the best

elements have a small percentage of light reflected

so lens flares are light reflecting inside of our lens

so the number of flares you can technically have is

I believe the number of elements times itself minus 1

or some sort of mathematical equation like that

because for every ray of light that enters

it can reflect off the first element

and then reflect off the filter

or can go through the first element

reflect off the second element

bounce back

reflect off that element

and then go through

or it can bounce again

and again and again

and again and again and again and again and again

so what's happening

is that a certain percentage of this light

is bouncing all over inside of our lens

and it might go through one lens

and bounce off the next lens and go through yet another

another element

bounce off that element

and then finally hit the sensor

so as you can see here

an incredible amount of reflections going on

and the refractive element and the

bending of the light is also affecting these flares

so a pretty complex interaction with a lot of physics

and a lot of re

casting necessary to get photorealistic flares so again

we're not gonna be able to do all of that just yet

what we're gonna focus on are the more

salient elements of the flare

in our case

we do not have such a direct light source

so we're gonna be focusing on these angular flares

that we get when there's a light source

outside of our frame or

uh perpendicular to our frame

so in the cinema world

most of our lenses are quite complex

and the more elements we have

the more flares we can have

so some of our lenses are

a simple four element lenses

and those will exhibit much less lens flaring

then say this kind of a zoom lens

which probably has around 15 elements

now better or high quality

lenses will have less flaring and less light leaking

and lens hoods will also help with flaring

so if you're trying to match

either of those two environments

you can have less light flares or lens flares

one last thing that again

we're not gonna be able to touch too much

because again

this is a more complex interaction

but lens flares do decrease the contrast and decrease

the saturation

you'll notice that

uh our color or our picture here is desaturated

and de contrast or we're

uh moving towards a middle gray

because lens flares

add light without any discrimination of the

objects in our scene

and so we lose contrast

we can get flares

and we lose saturation whenever we have heavy

lens flaring

so that's always something to keep in mind okay

enough talk

let's go into nuke

so to begin with

I like to identify what

the brightest parts of my image are

since those are going to cause flares

so if you have an obvious

object like the sun

uh in this case

we have our reflections

we can turn on zebras

and see we have

a few different areas of intense flaring

if you're not sure what the brightest pixel is

you can use the curve tool

which is a great tool

and we can change the type to Max Luma

and let's just calculate the max Luma for this frame

frame 82 and if you go to the

um max Luma data

you can see that this pixel right here

has the highest color value

so this is likely where uh

one if not all of our flaring is going to appear from

so again that's just an optional

way of actually measuring the color information inside

okay so now that we have that data

let's now track this

so I'm gonna drop in a tracker note

uh because obviously

the flare moves with the brightest element

we could actually do this with the maximum pixel

so let's run this out through our entire scene

I have a feeling that

what's going to jump between this area here

and the front of our ship

uh but I'm not 100% sure

so let's just try and run this for

let's say 50 frames

so let's go 50 to 100

and nuke is gonna run through that

and while it does that

I'm just gonna pause the video

as you can see

this does take a few minutes

so you can uh

save time by tracking what you want

or if you're relatively sure

the maximum pixel is gonna stay consistent

you can use this automated process

okay so as we can see here

our maximum pixel is jumping around

uh to various parts of our image

so we're not gonna use that

so it's now take a look at our tracker

and of course

we have a course completely

dedicated to the tracker node

but it's a relatively easy node to use

especially when tracking these kind of highlights

so I'm gonna decrease the size of the pattern area

increase the size of the search area a little bit

and let us track

so I'm gonna track backwards and then track forwards

so once this tracks through

uh I'll unpause the video and we can continue on

now actually

my track kept failing

so uh the tracker doesn't

really like high dynamic range values or

values outside of the normal 0 to 1 spectrum

so I'm just gonna clamp this before we track it

and then we can remove the clamp later

um and that's just so the tracker has a little bit

easier time with the data

so if you're having trouble tracking uh

a highlight that has high dynamic range information

you might wanna go in and

uh clamp that data

so the track has

uh sort of a

better number space to work in

now at certain points

the ship is gonna begin moving rather quickly

so you might need to increase the size of your search

area or update your

uh pattern location as we had to do here

now I'm just gonna let this track finish out

and once it's done

I'm probably gonna track one more area

I'm gonna track the gun portion of this

so right here

I think I'd like a lens flare coming off this as well

let's cancel this for a second

right this area

so I'm gonna track that

and then let's actually jump in the next lesson

and begin adding in our flare

so once you have both of your tracks or

whatever you want to track tracked

let's now jump into the next lesson and take a look at

how we can add these lens flares with our tracker