How to Key Green Screen in Nuke using Keylight (Basic)

[Music] hi everyone welcome to Johnny how-to so today we're going to take a look at Keene inside of nuke using the key light node and the key light node is especially helpful when you're trying to key out things that have partial transparency or aren't particularly opaque in this case we have this girl's hair the strands of hair we want to try and keep and before I get any further this is from this still this is just a still image no animated properties to it in the background it's from a miniseries called Merlin which was released by Lions Gate Entertainment I believe way back when this is old shape tutorial media so I want to make sure and give credit to them for having this alright so let's go and take a look at what we have so I'll press 1 on my green screen footage press spacebar to go full screen I'll press F to fit it to the window that I have here at a whole integer value of 100% in this case so I press R for red G for green B for blue a for alpha I can see I'll use plus and minus to zoom in the footage itself pretty clean has a little bit of fringing along the edges right here but not much at all so the red channel a little bit green channel pretty clean obviously and the blue channel a little bit of fringing but especially for the time period especially being shot for TV and as far as the quality of the light on the green screen very very good footage for us to work with if we were to adjust the gamma sliders a little bit here in the exposure sliders we can see that there's some noise on the screen that's probably noise from actually being filmed and then just texture on the green screen itself so but overall this is wonderfully shot green-screen spluttered so we should be able to get pretty decent results with this so like I mentioned earlier we're going to use the key light node in order to do our Keen in this case and this has a number of inputs on it you don't have to use all of them we'll use some of them but I'll give you alternatives as well but the one you for sure want to use is the source which means what do you want to take off of a blue-screen or green-screen so I'll go ahead and plug that into our green screen footage and we're going to start with that so I'll press 1 to view it and I'll double click on the key light node to see its properties and we have a number of options especially flip-down all these triangles they can be a a bit overwhelming and all the options you have honestly I don't tend to use all of these I use a set of these and then I use other nodes after I pull my initial key to get the rest of the way there but we'll talk about some of them as we're going through so first off most important one is screen color meaning do you have a blue-screen or green-screen certain tiers like prymatt will take out any particular background color whatever it's red green blue pink whatever it might be whereas the key light node is optimized for shades of green or shades of blue and to tell what color our screen is we need to go ahead and click on this black color swatch right here still we get the little eyedropper and now we hold down ctrl + alt and remember I'm viewing my key light node so I can see the result hold down ctrl and alt I'm gonna go ahead and left click somewhere on the green screen trying to stay away from her hair and we'll go ahead and take a look at our initial result so it's a little bit hard to see I mean you can definitely see there's stuff left over but we're gonna view our alpha channel press ok for alpha I'll press spacebar to go full screen so I can see that there's a lot of green screen left over still we have the upper right screen right upper left lower left lower right there's a lot left over and I'm gonna hold down ctrl alt and left-click and drag hold down control and just left-click in particular spots to tranq this better be kind of see that we're never gonna get everything that's it a pretty good job of getting overall as closer but I'm guessing when we probably lost some hair detail over here you can see if I go and click over you can see there's more hair detail that we lost when we got that one that got everything black so the tricky part is we want to get the background of black and the foreground to white but without compromising and losing this hair detail so the first thing we can do to make things a lot easier on herself is that in the original footage we don't really have probably 3/4 of this shot or at least half of it we don't need to worry about at all all this over here we don't need to worry about all this over here we don't need to worry about we only are interested in the area directly surrounding the character so the first thing we use is what's called a garbage matte meaning we're gonna draw a roto shape there's other ways to do as well but when drawer ownership and say hey we don't care about all this garbage outside the shape only what's inside of it so I've already set up if we go ahead and look at the the footage is 720 by 576 I've already set up my project signs of process for settings well down here parties set up my resolution for my project size to that so if I go and press o to add a roto node it's going to default to that size so with this selected I'll press spacebar to go full screen press plus a couple times to get closer I'm gonna go ahead and draw a shape roughly around her area but making sure not to get too close to where I'm going to cut off any of your hair detail and I think this is hair kind of jumping up here right here so I'm gonna go around that as well now if this was animated I'd want to make sure and animate this through the image sequence but since this is one still frame I don't have quite as much to worry about now the other thing to mention is I don't want to get like all the way over here and try and trace it perfectly because that's the whole reason we have it against the green screen we don't want to get too close because we want the keyer to take care of the actual perfect edges and the transparency of the hair we're just helping it by saying hey we don't need to worry about any of this outside of here we never have her moving these areas and so we're gonna get rid of that from the get-go alright so how do we use this so first off I'm gonna double click on this and over here there we go let's go over we'll go to the node tab and under label I'm gonna go and call this G matte or garbage matte just so I can know what is this photo shape for it's for the garbage matte ya know press F to fit this and there's a couple ways you can apply your garbage matte we'll go ahead and use the key light inputs on it right here so it's called out matte or a garbage matte they're kind of interchangeable plug this guy in if I view my key light node nothing is happening and it hasn't gotten rid of all this junk that's because in the key light node itself double-click to open its properties under the out matte component you can see it's set to none now when we were using this roto shape we're creating an alpha channel with our shape so it makes sense we go ahead and use alpha but when we do that you can see it actually has it backwards it's gotten rid of that all the stuff we wanted to keep and it's kept all the garbage that we wanted to get rid of so it makes sense we want to go in and invert this and now we have the selection that we want now if I go ahead and flip down the triangle here so I don't see that outlines for the roto shape you can see that we have a very sharp edge here and obviously we need to clean our matte but one thing to mention is typically almost always I can't think of any reason why you wouldn't I selected my roller ship and sp4 blur I'm gonna select the channels to blur is the alpha or usually always going to blur alpha to make it a softer selection and if we have this on our background it's going to bleed in or feed into our background a lot more smoothly than if we had this razor sharp edge from our roto shape without being blurred so I'm going to leave this unblurred for now or at least without this pumped-up for now I'll go and select this blur node and press D for disabled because for now I want to try and key this without having to worry about selecting partially blurred pixels and let's go ahead and start trying to get this so the challenge is we want to keep hair detail on both sides but we need to get the background of black and we always need to make sure that the actual interior of the character is why it is one if we darkened down our viewer we can see that there's still transparency and her quite a bit so sectioning off your keys is another thing that can be really helpful we're not going to do that in this particular video at least maybe just for a little bit let's go and talk about how I can get this going so let's go ahead and see if we can at least just for this example if first time using key light we can get a decent key and see whatever salts up so I'm going to ctrl F click see how I can do I think I might be cutting off a little bit of her hair right here so I'm going to drag this up a little bit there we go and we'll make sure we're back on our key lights and let's see if we can find a spot that looks like we're getting most everything that we want at least a good starting point that looks pretty good we're getting we're keeping that here dick hair detail here most of this is here there's maybe a few strands we're missing here and there but overall we're keeping a good amount of it now again what I'm gonna do here for this first tutorial is not ideal but I don't want to get too complex in this very first example so first off we pump up our viewer luminance we can see that we still have a lot of the green-screen left over we can get rid of that by flipping a little screen matte button right here or a triangle and if we clip white now if we do click black it's going to push things that are close to black all the way to black but you can see the further we go we start eroding away the detail that we're trying so hard to keep so we pretty much lost all over here detail and as you can imagine our results not going to look very good now if we had Samuel Jackson and the Star Wars prequels and he had no hair then now maybe that would be a little bit more acceptable but so we're gonna push this as little as possible probably just a little fraction and maybe we'll stick with something like that somewhere around there so we still have some green screen left over here we have some green screen left over here and we do have some left up here remember I have this pumped up 248 percent if we view it normally there's not nearly as much left as we thought now if I was to put if this was animated I put this on a background and I could see this noise chattering and animating then I would need to fix that but in this case I don't know what it looks like animated over the actual intent background we'll just say that's decent enough for now we could go ahead and if I click to the right of this number right here and use the up arrow key I can up it just a little bit at a time or to the left of it I can have it just a little bit by little until I see that I'm starting to lose more hair detail and I try and back off at that point so maybe we'll get be able to get a little bit more and let's go ahead from here let's view this on some different background so first off here's our result and if I merge it well this is a good way we can see how it is comparing to original footage someone make a constant so impressive tab and that constant which is like a solid and After Effects now I'm gonna make it the same color as our original green screen so I'll double click on the constant click on the eyedropper control and left-click on the backgrounds gotta change the constant that color let's go ahead and just merge this on top of that now I could do this inside the node so I could just select the background node background pipe and plug it in there and just view it and I need to change my key light from final result to composite and that'll put it on there but I think in this case I'm gonna go and just change keep it on final result instead of using the background input I'll go and just merge it on top so select the key light in for merge now I'll put on top of the B input and basically the same thing sometimes key light does some nice things in actually doing the composite alright so let's go and take a look so if i zoom in and I'm gonna try and do this at a whole pixel value and I pressed 1 and then I select my original footage and press 2 and then I go ahead and in the viewer press W for white I have this wipe where I can wipe from one side to the other so you can see over here is me putting it over this back all right here the composite the 1 and then over here is the two this is original footage so am I losing a lot of the greens fledge will press spacebar to go fullscreen well it looks like I'm not losing a whole lot over here doesn't look like I'm losing much looks like most that hair details being retained so like that sides working well I mean we're using losing a little bit here but not too much and on this side I press + to zoom a little bit more it looks like we're losing a little bit of his hair detail like this strand right here which if this was animated and moving around that would be an issue we don't want pieces of hair or strands of hair just kind of going in and out of visibility but not too bad for just trying to do this all in one key now again we still do have some noise left down here and we can kind of max it or amplify that to see a little bit easier by turning down the luminance over here doesn't look too bad again we still have some noise in the lower left here we would ideally pull a separate key for over there but not too bad and again we're not really losing too much hair detail which is ideal losing just a little bit all right so let's go ahead and press W to disable our wipe we'll go back and so not too bad another thing way that we could check this if we're using something that's a little bit or at least oftentimes is helpful is will make another constant I'm gonna make it somewhat of a neutral grey so we're gonna go ahead and click on the color wheel I'll just put this somewhere around halfway and we can go ahead and do this on this as well so instead of the B input being the green background I'll go and use the gray background and this sometimes can be useful in diagnosing do we have a lot of noise leftover anything like that as well so I mean overall we're doing pretty good we again we do have noise here let's go ahead and see obviously the ultimate test if you're lucky enough to have the final background when you're doing your key is to put it on on top of the background so let's go ahead and take our Merlin background right here and let's merge it over that so go and take my B input plug it into the background that's intended to be on and again I could absolutely do this instead of using the merge node I could just plug this in the background because I feel I'm happy with my key and inside the key light note itself go ahead and just change it to composite and we can go ahead and take a look at it here so I mean it doesn't look too bad obviously the color correction between her and the background doesn't match and so we're gonna go ahead and remedy that and just because I like to use different color correction tools not just what's built into the key light note itself I'm going to go ahead changes back to final output I'm gonna go ahead and say this is my input above this is my B input below and I'm gonna go and do my color correction in between when it comes out of the key light for the the girl and on the way to the background itself so one thing that we need to do I'm not going to get into too much in this video is right now all be green pixels or at least the pixels that are partially hidden in the Alpha Channel that are transparent those aren't if I try and color correct this as is it's not going to get color corrected the same amount as these areas that are completely white and one other thing I almost forgot to mention really quick is remember on the interior of her if I go ahead I want those gonna be completely white if I darken this down you can see there's still transparency inside her mask you may or may not notice that when she's on top of the background we want to make sure she's not see-through like a ghost so in our key light node under clip white we're gonna just the slightest amount until she's not see-through anymore you can see this is literally a teeny tiny amount like I've done this what is this like it's only several hundredths of a percentage so this is pretty much gotten rid of the transparency in her mask and while it looks like we've done a lot when I have the luminance turn all the way down if we look at it normally we've actually hardly adjusted anything at all but she's not gonna be see-through anymore so on the background I'll go and press a to go back to my color view on the way to the merge node I want to go and try and color corrector to match background more but because these pixels are transparent we need to use something before we do our color correction called an unpremeditated before it's pretty much making them fully opaque so anything that we color correct in this area where it's white in the off channel is going to get hit a hundred percent and since we aren't premultiplied all those pixels here are going to get hit a hundred percent by the color correction as well if we don't do that then these pixels only get color corrected a fractional amount on their transparency I'll go over that in another video in more detail explaining at some other time but so going out of braid note a color correction node and at the end the go ahead and add a pre multiply note so basically we're lifting off the transparency or color correcting all the pixels together at the same overall amount and then we're reapplying that transparency to those pixels that are transparent and put it on the background again that's a little bit confusing I'll cover that in a later video in the future all right so I'm gonna rush through the breasts this cuz I wanna make this video to horribly long we're already moving in on eighteen minutes let's go ahead and in the gray note itself I want to make sure that her color tint overall kind of matches and again there's many ways you can do this I'm gonna go ahead and click on the multiply key will and go ahead and try and move her into those kind of warmer regions somewhere around there for now and now we need to take a look if I pump this up you can see her black levels do not match the black levels the background and again it depends on some what the art direction they might say oh there's this shiny background that's lit behind her and so her black levels on the side that's not facing the light shouldn't be as as bright but in this case I want to try and lift them up a little bit to where they match a little more so our black point right here or our lift we go ahead and do that here as well I'm going click on the color wheel since lift affects your shadows more I'm going to go ahead and lift these up a little bit not too much and if you squint your eyes this helps a little bit I'm gonna go ahead and try and take it in that warmer direction as well just a bit and it's not gonna make a huge huge difference but we'll go ahead and try and get that in there just a little bit I go ahead and disable my grade now as I'm going along again see we're kind of going in the right direction and now let's go ahead and go the opposite spectrum I want to make sure that my highlights are kind of matches as well so if I go ahead and pump this up as these highlights and the backgrounds start to flare towards right white we kind of want or start clipping we kind of want her footage to start to do that as well so we can see that her skin tones or highlights are starting to hit that around the same time so we're not super far off there and if we go in and click on these guys to reset them we're actually not in too bad of shape right now you know we always want to go channel by channel and take a look as well so press R for red does anything look grossly out of place mmm again her black levels might be a little bit too dark but again I'm gonna go with the background is really bright and she's on the opposite side of that G for green doesn't look too bad B for blue alright doesn't look too shabby overall we might adjust her a little bit more but again for a very first video into the key light node I don't want to dig too much into color correction and unpromoted and then premultiplication all that stuff so for here we'll go ahead and stop this here hopefully this has been a little bit helpful and giving you a very bit of insight in the Keen process again we would cover this much differently if we were really trying to do some production we would do different keys four different sections we would piece them together would try it get rid of all the green spill and really color correct really really in-depth but hopefully for a very first intro to keylight this has been helpful thank you for watching and I will see you on the next Johnny how to you

Channel: Johnny HowTo

Views: 15,009

Keywords: how to key green screen in nuke using keylight, johnny howto, cg, vfx, tutorial, how to, learning, filmmaking, step up, master, tips, merlin, nuke, compositing, visual effects, chroma, key, keylight, foundry

Id: jayZs6dFdP8

Length: 19min 41sec (1181 seconds)

Published: Wed Jan 01 2020