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in this lesson
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we're gonna learn about everyone's favorite topic
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lens flares
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so even though I'm sure everyone
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understands what a lens flare is
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I just wanna take a look at a few examples
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so whenever there's a very bright
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element inside of our shot
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there's a high chance that that element will begin
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reflecting through our various lens
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elements and lead to flaring
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so we can see here
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we've got some spike flares
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we've also got these aperture shapes
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uh that are very subtle in this case
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now if we take a look at this video here
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we can see uh
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a much more uh
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explicit lens flare
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and you just
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you can see it looks like there's a 1
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2 3 4 5 6 7 bladed aperture on this lens
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and as you can see
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some of these flares have some very complex
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characteristics
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as the camera is moving
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we're not gonna be able to get into
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uh all of these characteristics
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as you can see
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it's incredibly
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uh complex interactions
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so how do lens flares come about
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well if we take a look at our lens
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we can see again
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we have our glass elements
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and glass and
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somethings by nature are reflective and so
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what happens is these glass elements are highly treated
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highly coated
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highly processed to not be reflective at all
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because if they are changing the image
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then it is not a true picture of what is happening
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but for very bright elements
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when there's an incredible amount of energy
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like with sun or spotlights pointing into our camera
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even the best
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elements have a small percentage of light reflected
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so lens flares are light reflecting inside of our lens
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so the number of flares you can technically have is
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I believe the number of elements times itself minus 1
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or some sort of mathematical equation like that
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because for every ray of light that enters
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it can reflect off the first element
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and then reflect off the filter
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or can go through the first element
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reflect off the second element
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bounce back
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reflect off that element
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and then go through
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or it can bounce again
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and again and again
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and again and again and again and again and again
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so what's happening
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is that a certain percentage of this light
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is bouncing all over inside of our lens
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and it might go through one lens
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and bounce off the next lens and go through yet another
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another element
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bounce off that element
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and then finally hit the sensor
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so as you can see here
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an incredible amount of reflections going on
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and the refractive element and the
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bending of the light is also affecting these flares
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so a pretty complex interaction with a lot of physics
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and a lot of re
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casting necessary to get photorealistic flares so again
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we're not gonna be able to do all of that just yet
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what we're gonna focus on are the more
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salient elements of the flare
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in our case
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we do not have such a direct light source
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so we're gonna be focusing on these angular flares
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that we get when there's a light source
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outside of our frame or
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uh perpendicular to our frame
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so in the cinema world
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most of our lenses are quite complex
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and the more elements we have
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the more flares we can have
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so some of our lenses are
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a simple four element lenses
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and those will exhibit much less lens flaring
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then say this kind of a zoom lens
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which probably has around 15 elements
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now better or high quality
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lenses will have less flaring and less light leaking
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and lens hoods will also help with flaring
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so if you're trying to match
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either of those two environments
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you can have less light flares or lens flares
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one last thing that again
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we're not gonna be able to touch too much
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because again
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this is a more complex interaction
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but lens flares do decrease the contrast and decrease
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the saturation
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you'll notice that
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uh our color or our picture here is desaturated
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and de contrast or we're
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uh moving towards a middle gray
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because lens flares
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add light without any discrimination of the
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objects in our scene
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and so we lose contrast
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we can get flares
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and we lose saturation whenever we have heavy
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lens flaring
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so that's always something to keep in mind okay
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enough talk
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let's go into nuke
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so to begin with
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I like to identify what
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the brightest parts of my image are
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since those are going to cause flares
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so if you have an obvious
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object like the sun
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uh in this case
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we have our reflections
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we can turn on zebras
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and see we have
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a few different areas of intense flaring
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if you're not sure what the brightest pixel is
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you can use the curve tool
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which is a great tool
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and we can change the type to Max Luma
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and let's just calculate the max Luma for this frame
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frame 82 and if you go to the
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um max Luma data
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you can see that this pixel right here
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has the highest color value
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so this is likely where uh
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one if not all of our flaring is going to appear from
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so again that's just an optional
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way of actually measuring the color information inside
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okay so now that we have that data
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let's now track this
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so I'm gonna drop in a tracker note
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uh because obviously
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the flare moves with the brightest element
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we could actually do this with the maximum pixel
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so let's run this out through our entire scene
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I have a feeling that
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what's going to jump between this area here
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and the front of our ship
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uh but I'm not 100% sure
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so let's just try and run this for
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let's say 50 frames
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so let's go 50 to 100
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and nuke is gonna run through that
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and while it does that
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I'm just gonna pause the video
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as you can see
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this does take a few minutes
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so you can uh
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save time by tracking what you want
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or if you're relatively sure
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the maximum pixel is gonna stay consistent
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you can use this automated process
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okay so as we can see here
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our maximum pixel is jumping around
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uh to various parts of our image
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so we're not gonna use that
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so it's now take a look at our tracker
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and of course
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we have a course completely
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dedicated to the tracker node
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but it's a relatively easy node to use
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especially when tracking these kind of highlights
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so I'm gonna decrease the size of the pattern area
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increase the size of the search area a little bit
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and let us track
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so I'm gonna track backwards and then track forwards
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so once this tracks through
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uh I'll unpause the video and we can continue on
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now actually
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my track kept failing
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so uh the tracker doesn't
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really like high dynamic range values or
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values outside of the normal 0 to 1 spectrum
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so I'm just gonna clamp this before we track it
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and then we can remove the clamp later
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um and that's just so the tracker has a little bit
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easier time with the data
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so if you're having trouble tracking uh
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a highlight that has high dynamic range information
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you might wanna go in and
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uh clamp that data
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so the track has
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uh sort of a
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better number space to work in
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now at certain points
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the ship is gonna begin moving rather quickly
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so you might need to increase the size of your search
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area or update your
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uh pattern location as we had to do here
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now I'm just gonna let this track finish out
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and once it's done
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I'm probably gonna track one more area
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I'm gonna track the gun portion of this
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so right here
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I think I'd like a lens flare coming off this as well
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let's cancel this for a second
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right this area
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so I'm gonna track that
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and then let's actually jump in the next lesson
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and begin adding in our flare
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so once you have both of your tracks or
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whatever you want to track tracked
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let's now jump into the next lesson and take a look at
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how we can add these lens flares with our tracker
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