Face Replacement?

HeySiriHeySiri Website User Posts: 382 Just Starting Out

In the film I'm making everything is very dependent on scheduling because all my actors are students who have wildly different schedules. After a fight scene, they remove one soldier's helmet and it's revealed the soldier was human (they thought it was an alien). This is a crucial plot point, and there has to be a human face. But, the actor playing the soldier is also the main character (who's not in that scene as the MC) but I need someone's face to be shown (I'm already playing another minor character who dies early on myself). It's complicated, but long story short I need to do some sort of face replacement because I can't rely on yet another person's schedule for filming. How would I do face replacement for a few frames? It could be a static shot and almost any angle. That part's not important. And I can go to school and take photos of someone's face to track over or whatever, but I really don't know what to do.


  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,293 Ambassador

    You're over thinking this, dude. I know you already know how to do this. When I finish this breakdown you'll see what I mean. 

    Ok, so this is a helmet removal of a dead soldier, so you've made your life easier in that you're not trying to do a face replacement on someone moving and talking. 

    You've also made your life easier by recognizing the shot can be static. 

    The next bit is a little shot planning - you don't show the face of dead soldier as the helmet is removed, you show the reaction of whoever removes the helmet, they realize the mistake, and THEN you cut to the body. 

    Great, take your angle of the body. Make your life even easier and shoot this as the POV of whoever removed the helmet - so a more-or-less straight on shot of your temp actor. Avoiding odd angles will make the match easier. Do this on a tripod, and make certain you get a clean plate of the floor with NO actor. You might not need it, but better to have it (this is a general rule). 

    Take a note of camera settings - especially ISO, white balance and aperture (f/stop). Shutter speed is less important here. You'll want to match camera settings as ISO affects grain, aperture DoF and white balance color. In-camera matching will reduce color correction later.

    Now you need to shoot the replacement face. So dump out a frame of your temp actor and either print it or throw it on a phone/tablet for reference. 

    With your reference you can lie your replacement face actor down then match angle and lighting as best you can. If the Composite is going to only a second or two, you can probably get away with a still, but shooting video will provide a moving grain/noise pattern.

    Ok, so, in Hitfilm load the two clips. Replacement face on top. Mask around the face. It can be rough right now. Move the anchor point to the pupil of either eye and set opacity to 50%. Position the eye with the anchor point over the correct eye of the BG plate. Now you can adjust Scale and Rotation of the replacement face to line up. Since the anchor point is on the first eye you lined up, this will be easy.

    Set the top layer back to 100% opacity then refine and feather your mask. 

    Now, in my work as a karaoke host I used to do parody movie posters where I replaced face of >actor< with my own. Here's a couple of things I've learned from experience. The most important thing to match up is the position of the eyes. If the eyes line up a little mismatch of nose and mouth won't be noticed. That said, getting a near match on the nose and mouth is important. BTW the tip above about moving the anchor point over an eye? It took me way too long to figure that out for myself. 

    If both actors are fairly close in skin tone and you match the lighting pretty well in-camera you don't need a full head replacement. If you just mask around the eyes/eyebrows and down the plane of the cheeks to just under the mouth, then you can feather out the mask, but leave most of the forehead, chin, and jawline/ears of the original plate and no one will notice. This keeps the interaction of body/ground on the background plate and will help sell the effect. 

    If your actors have radically different skin tones (possibly hair), then you'll need to be more precise in masking - you'll have to trace the entire head and neck. This is also where your clean plate might get used. If your temp actor has (say) a fluffy head of hair and your replacement head has a buzz cut then you'll need the clean plate of the floor to remove the hair. 

    Then you go into final color correction. I'd use Curves. 

    Remember you can mask grade layers and use color correction filters to brighten or darken areas. This can be used if you need to correct a cast shadow, or even to mask in shadow/highlight areas in the overlaid face. 

    So, by now you should see why I said you pretty much already knew how to do this.... Cuz you're basically just going to line up a top layer, mask it and color correct.

    If you needed to do a head replacement on a moving/talking actor - well, then things would get annoying and complicated, but, for a face replacement of a "dead" guy, you can treat it as a photo composite. And that's easy! 

    Finally, once the comp is done you can toss a Grade Layer on top and add a Shake effect for a little camera wobble. Just a bit. ?

    You got this. 

    I'd even say you can practice this just by downloading a couple of random still pics from online and doing a face swap!

    Below is a GIMP tutorial on face swaps. Here's a couple of observations based on this tutorial:

    Note that the two faces being swapped aren't lining up quite correctly - one looks straight at the camera, the other is angled. But you'll want to watch around 2:20 in when he starts masking - he'll mask the eyes, nose, mouth and part of the cheek from the overlay and leave the jaw, ears, neck and hair of the background layer. This demonstrates what I wrote above about how if you match the EYES no one will notice if the nose and mouth are a bit off. 

    At about 3:50 the tutorial shows another way to match skin tones. Do do this method you'll duplicate the top face, run a Fill Color effect (using the eyedropper to select a color from the bottom layer) change the blend of the top layer to Soft Light, reduce opacity, then subtract mask eyes and mouth. 

    Don't worry about the rest of this tutorial. It's just masking. GIMP uses pixel masks that can be brushed, Hitfilm uses vector masks that need to be traced. The tutorial will use erasers to refine the mask shape, you'll adjust mask points. The tutorial will use a blur on the mask, you'll use a feather. Same result. 

    Again, you got this. And another reminder you're doing it RIGHT by testing, planning and asking questions before you shoot. It's sometimes heartbreaking to get user questions on how to accomplish an effect after the footage has been shot....incorrectly. VFX success begins with planning, and you're planning*. 

    *OK there are the VFX artists who can "wing it," but those are experienced artists who worked with meticulous planning long enough where certain things are second nature... You'll get there. It's just gonna take time and experience. 

  • JBaymoreJBaymore Website User Posts: 335 Enthusiast


    I'd humbly suggest that Triem23 get into the credit roll on your movie.  (Some others here too.)

    WOW......... 'above and beyond' as always @Triem23.





  • HeySiriHeySiri Website User Posts: 382 Just Starting Out

    @JBaymore @Triem23 I was definitely thinking of a credits section in my movie that acknowledges a lot of people from these forums!

    Well, that doesn’t sound too hard at all! And it’s only the actor’s face, their mask is removed but not the full helmet. So hair and neck aren’t the issue at all. And the actor in the suit and the person I was going to replace them with have somewhat similar features. I’ll definitly do some practice beforehand though.

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