Nuke tips & tricks l Saturation Keyer l Keying without a greenscreen l sky replacements

hey guys it's Shonda hunt here and today I  want to do a quick demo where I show you how   you can key using the saturation key with the  keyer note we use the key or set to saturation   sometimes when you're doing Sky replacements  and you don't have a blue screen or green screen   the saturated and you have elements of hair or  something that's going over different colors in   the plate and you have to try to pull all these  out of course we can get rutle for some of the   tighter areas but for all this hair that's blowing  around what we would want to do is try to get the   hair separated out and we can try to pull Keys  we might have some problems especially once the   hair starts going over this rock so I want to show  you guys this method of using the saturation um to   keep pull your key so I got a few frames playing  here just so we can see the hair blowing around so we have a little hair movement and I do have  it built out I will walk through this process but   let's look at the final result over here some of  my mats might cut out parts of her hair but you   can get the overall picture I haven't um animated  these mats or spent much time making sure the mats   were covering the area but overall we can see  that we're getting some of that hair detail back further color correction adjustments  could be done to the plate to get these   bright edges away or you can use some  other comp techniques to get those away   and this demo though we're just focusing  on these straggly hairs that are blowing so let's dive into this   so the process that I used for um keying with the  saturation is first I do have it set out here but   let's walk through the whole process over here  so the first step is to make a color space no and what you'll want to do is change your output color space to HSV so this  will allow us to see the Hue saturation and   values and differences of those in this in our  plate so as you can see the different values   are separated out by different colors so it's  very easy to see we want to keep her here and   then the sky and a lot of the things around it  including the water are kind of this pinkish color   so what we want to do is go ahead  and create a hue correct node and then we're going to  focus on the saturation tab   what we need to do is we need to go ahead and  Sample a pixel of the areas that we want to   um key out so let's hold down the control key and  Sample a pixel we'll sample one that's kind of   close to our hair just so that we have that value  and we can see here that this is where that value   lies so if you hold down control or not you can  create a new DOT and then you can bring that down so now we see that pink color has changed  and that's actually exactly what we want um pink here that's being picked up from the water  so let's see if we bring this one down so that's   not really giving us what we want we could simply  sample that sample another pixel and that'll show   us where that value is so it looks like it's  over here so let's see if we bring that down great so we kind of have this pink color that was  around the hair we now have most of that removed   and now we can get into this saturation key it  looks like we may have lost some values there   but that's okay for now because usually I use this  saturation key in combination with the IBK setup   and I love using the IBK here to um give me the  edges that I need the IBK does a really good job   um usually of maintaining the edges so I'll keep  that for now I'll just try to pick up as much as   I can with this so now we have our color space  known and then we have um our Hue correct where   we took out the color that we want to mostly  take out from the plate now let's create a cure and now that we have that here let's go ahead and  look at it so it's set to luminance by default   but we want to change it to saturation and now  when we change it to saturation we already see   that this is looking like it's going to work  and of course we could break this up where we   um do one section of hair and then maybe we  want to create another saturation for this   part of her hair but for now let's see what  we can get just as one overall adjustment so I'll go ahead and start pulling this back and  actually those values are going away pretty well   now what I want you to pay attention to though is  that even though I'm crunching this up the values   around her hair are staying pretty consistent  of course if I take it too far they'll start   changing but overall it's not really affecting  those pixels where her hair is because of course   those values are different so that's why we want  to separate those values out first so that when   we're pulling this key it's still retaining the  pixels around her here so we can leave it here   or we can go further I would usually use another  cure or even just use some Roto for the core for   here but for getting these edges which is what  I'm focusing on here I'm going to use this method so there let's see we have  her here pretty much out okay so that's the first step that we do and I'm gonna go ahead and just  connect actually let me turn this off   I'm gonna con actually I think I'll just  copy this I'll make a new one so that we can   reference back to that one without having  to reconnect it again so connect our Alpha so when I'm doing my um mats I'm  often using the copy Premont workflow   and then we can take a look at how this is looking and now we'll know how much more  we want to adjust these values to bring more details back so overall you know you can play with this to get what you need from this you won't really get all of the hair back so  this is just a good technique to grab patches   of the hair like you could start at the top  then you could try another setup using these   same nose just different adjustments to start  bringing back the hair in different places now let me show you how I would go ahead and  then use the IDK to mix in some more Edge detail   so I have it set up here where I  first start by creating a constant   so I'll go ahead and make some  space here I'll create a constant then I'll pick an area from the plate where I  want to sample now I would have to since   there's a gradient or different values of  blue in this Sky it's best to Target one   area at a time so I'm going to focus on this  area then I probably create another constant   for this area and then if I wanted to try  to get some of this Blue Water I would also   create another constant color for that area for  now let's focus on this top area of her hair and you can hold down control again to  sample the color value for that area we'll create our IBK Gizmo connect the  color up and connect it to the plate   and let's see what we have so this is where we  are it is set to Blue for now I'm going to start   merging my channels together so that I can look at  my final output and make the adjustments as needed so I'll see what areas of the IDK are looking good   and then I'll mask those out and I'll  use specifically those areas for my neck   one thing that I do like to do is I like to go  ahead and add a great note right after my color   so that I can start adjusting the color to see  if I'm getting something better or something   worse so it's very easy just to start fine-tuning  that matte by adjusting the color with the gray   if we turn that off we didn't have any of that and  now we're starting to get some of that detail back so that's looking good in this area  where we sampled that blue color   so you would want to go ahead and then mat  out that specific area only the area that's   working good we can create another setup for the  other areas just so we have a little more control and now if we take a look at what we have here we're getting something close I'm going to go  ahead and just mask around her head so we're not   distracted by all the other stuff that's going  on in the plate as we're building up our mat so I'll just mask this out for a  second so we have a better idea   change that to mask and good now we're not so  distracted because we are piecing this together and this is how it's looking for now with  these two adjustments we might even want   to start key mixing in some stuff here  let's keep that and let's create this same IBK setup so that we can sample a different color I have a feeling we want to key mix this  one in but we'll see how it's going let's overall I'm always just playing with the values  and I'm also playing with different merge   techniques so that I can see what  exactly is working and what's not and what operation is giving me the best  results so let's take a look at this one   okay so now we we went ahead and key that  area let's see if we adjust this grade what are we going to get this off for now okay so remember we're only  focused on these hair edges let's see how this   grade is looking okay so we we're not going  too far with this with this um IBK and then if we go to what we had before so it's kind of just filling in a little bit  more so we'll go ahead and merge that channel in   so we'll do another Channel merge okay so we did fill that in and honestly we have  a little bit of a good patch for the hair let's   let's look at the alpha Channel so the hair is  kind of filling in pretty good we could also   just add a gray if we wanted to make some overall  adjustments to try to bring down a little more but I wouldn't really want to do this too   much because I want to make sure  I'm keeping the fine hair detail so for now this is what we have so  using the same process of steps of   um using the saturation key and  then using the IBK color to try   to bring in some more edges I use  that same setup here so I have my take a look I spent a little more time  dialing these in so I have my saturation key   then I added an IBK for that patch of hair  the same steps I was just going through   then I added another IBK for that patch of hair  and then I went ahead and just created a mask   around her so that we can cut out a garbage mat to  cut out everything else around her on the plate so   this is actually looking pretty good now one other  step we do have this blue around her you could   go ahead and try to color correct that a little  bit so it's blending in with your new background   I just went ahead and added a key light adjustment  to also get rid of this blue haze that's in her   hair and you see it's doing a little bit um of  work in the background to bring some of those   values more neutral so we're not picking up too  much of that sky that we're going to replace and now we have a pretty decent mat of again  we're just focusing on the edges we can Roto   very easily to get a Core mat for her but  these fine hair details are usually a little   bit tricky so I found that this technique  is pretty good at picking up those details   and there are some tools that you  can use to smooth out the strands   such as the real smart immersion blur I don't  have that plug-in on my computer to show you but   there's some tricks to bring this in a little  further but this is actually a good starting   point and this is simply with the tools that are  available in Nuke the key tools and just combining   a few methods let's go ahead I am going to play  this out so that we can see how it's looking as far as some of these straggly hairs   and we will see aside from the areas  that my mat are going to cut into   my roto shapes um it's doing a pretty good job  so we have some hair and we have some moving   here and you know depending on the background  the the sky that we're going to replace this   with we might be able to get away with a lot of  these highlights a lot of this bright color might   just blend in with our new background or you could  keep color correcting or adjusting it even further

Channel: Post Series: A Nuke course by Shonda Hunt

Views: 5,907

Keywords: #vfx, #nuke, #compositing, #vfxartist

Id: GnO3o2kNI98

Length: 17min 47sec (1067 seconds)

Published: Thu Nov 10 2022