Masking problem: mask outline visible

I applied a mask to a clip. The mask as such works but the mask's outline is visible (cp. screenshot - blurring in image is intentional). It disappears when I set the Blend to None, but then the mask disappears too, i.e. has no effect.
What can I do?
Thanks in advance.


  • I've noticed this too, in some instances the outline of a mask creates a thin line... Probably a bug.
  • Thanks Robin, so it's not just me. Any idea on how to prevent this, anyone?
  • edited June 2013
    If you adjust the Expansion setting of the mask a touch, does it remove the line, or just move the line?
  • Thank you fro trying to help!
    It just moves it, the line remains visible.
  • I've noticed mask lines showing up in other places, such as the new Chroma Key. I think if you crank up soften and a few others, they really show up :(
  • Just as rgbii stated, they show up very often in the Chroma Key.   But only in the preview and in the program. The final output looked fine as I recall.  It's been a couple weeks since I used Chroma key. 
  • I have used a combination Chroma Key and mask. The mask outline is rendered as well, so no luck here.
  • Hi all. Whatever happened with this issue? Just got ultimate 2 and noticed it?
  • I reported this issue about 11 months ago, but it still hasn't been resolved.  I'd really like to use the Chroma Key, but always run into this issue.
  • Can you get us a link to a project which shows this behavior, and the footage that goes with it?  
  • Try to increase the "feather" of the mask a couple of px. That works for me.
  • Can you get us a link to a project which shows this behavior, and the footage that goes with it?  

    To see the issue as it applies to Chroma Key, checkout ticket WMK-712479. It includes a project showing the issue.

  • Thanks, I took a look at that project, and I can easily get perfect results buy turning down the Softness, Expand, and Despot Foreground controls.  Increasing the Softness is going to bring some of the greenscreen back into the edges of your foreground, which will be turned to grey by the Spill Suppression - this is expected.  I'm not sure when you would need an edge that soft on your subject, but obviously that sample project is just a simulation.  Does anyone have an actual example I could look at?  I'm pretty sure this is an issue which can easily be avoided by adjusting the key settings.
  • edited June 2014
    Axel, bumping up the softness is what exaggerates the issue so it can be seen easier. That simple test obviously doesn't need softness, but it was much easier project to provide than one with actual footage since it clearly shows the problem.
    With the chroma key, the softness should effect the edge produced by the green screen, but it's also effecting the edge of the garbage matte.    If I'm using "Soften", "Despot Foreground" or "Erode/Expand" to clean up around my green screen subject, it should not also effect the edges of the garbage matte (mask), but it does, which becomes very obvious, making the chroma key difficult, if not impossible to use when using a garbage matte/mask and any of above mentioned controls that are part of chroma key. There seems to be a few other cases than just the chroma key, but that's where I first found it.
    Here's the simple project incase anyone else wants to take a look. As you can see, while the mask/garbage matte should simply eliminate junk at the edges you don't care about, the controls/settings used to fine tune the chroma key of the subject  also effect the edges of the mask.
  • Yes, I understand what is happening.  And I'm pretty sure that is can be avoided by adjusting the key settings.  I also understand that the sample project was put together specifically to make the issue easy to see, which is why I'm requesting a project with an actual example - so I can understand better why this is an issue and see if I'm correct.  Because I've done a bit of keying with Chroma Key and masks, and never had it come up.
  • So you don't see it as a problem that the settings effect the garbage mask edge in addition to the green screen subject?
  • I'm not saying that's how it should work, I'm trying to help you work around it.  To find an immediate solution to get your footage keyed.
  • The problem I had was 11 months ago, and I ended up using the older preset for green screening.  I'm not even sure which project it was :)     I've been sticking with the older method since then.  I'll try to remember next time I have green screen stuff to try both effects to see if I can find a good example.
  • edited April 2017

    I ran into the same thing with HitFilm Pro 2017 while trying the following technique I have used in Vegas Pro quite a few times: To hide a 3D object (including its shadow) partially behind a foreground element I duplicated the video track and created a mask around the foreground part. It works well except the fine line around the  masked foreground part. Played with every possible setting and it does not go away. Feathering the mask makes it worse.

    Am I using the right method? I can copy the mask to the 3D object and invert it. That works but then I also have to copy the mask to the shadow layer (and other obects that should also be hidden). So that does not sound too clever because every correction is really annoying...

  • No one? Am I doing it the wrong way?

  • Without an image of what you're trying to do and the problem you have... as well as Feathering the edge of the Mask, have you also adjusted the Mask expansion and/or adjusted the feather to be In or Out instead of Both?

  • Just found the reason while trying to reproduce the problem: Mocha was assigned to the video layer with the mask (without doing anything, it was just left over from trying different things). As soon as I remove Mocha - or set Premultiply to Off - it works fine.

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