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Masking

Posted: Thu, 6th Nov 2008, 4:59pm

Post 1 of 4

pscamm

Force: 2225 | Joined: 5th Nov 2006 | Posts: 300

VisionLab User VideoWrap User Windows User

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Hello all,
Hav'nt been around for a while, hope you're all well ?

I have a couple of questions with ref to masking if you dont mind.

1. Is there any tutorials on masking on this site which explains the process in detail, ie the important do's & dont's, when to feather & when not & what feathering does for your mask, should you do it zoomed in tight or not, pixels in a clip will be somewhat dithered between an actors arm and say the background/backdrop - Where should the mask's line be ? ETC ETC

2. Once the above is in your head and you complete an animated mask, (after lots of practice im sure LOL) I will want to output this mask as a plate of just black & white so it can be used to mask another clip. How do you render out this 'alpha' only channel ???

Thanks in advance for any help

Paul
Posted: Thu, 6th Nov 2008, 5:43pm

Post 2 of 4

Rockfilmers

Force: 2182 | Joined: 10th May 2007 | Posts: 1376

VisionLab User PhotoKey 4 User FXpreset Maker FXhome Movie Maker Windows User

Gold Member

These questions aren't a problem at all. Go to the video tutorials under support for your first question. For number two, are you talking about silhouetted shapes? I don't quit understand.
Posted: Thu, 6th Nov 2008, 9:08pm

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Axeman

Force: 17995 | Joined: 20th Jan 2002 | Posts: 6124

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SuperUser

Rating: +1

With regard to your first question, there are some video tutorials that cover masking here. I don't know that they go into much detail as far as the specifics about which you are asking, but those are areas where the correct answer will vary frequently, based on the specific footage you are working with in each situation, and trial and error may be your best teacher. For scenes where you are going for realistic compositing, generally its best to keep the feather pretty small. A very small feather (again, depending on the footage in question, and its resolution, and the size of the masked object in relation to the frame, the exact size will vary. Try starting with 2 pixels and adjust from there) can help blend a hard edge, but too much feather and it becomes counter-productive. The detail of the mask shape, as well as the degree of accuracy you require, will affect how much you want to zoom in while drawing it.

As far as your second question, there are a couple ways to do it. The first, if you plan on using the mask shape to mask another clip within VisionLab, you don't even have to render it, you can simply use an object mask to select the mask you have created as an alpha source. The masking tutorials in the support section cover object masks as well as the other standard msk types, so they should help you get up to speed.
Posted: Fri, 7th Nov 2008, 4:26am

Post 4 of 4

Mandalorian

Force: 1905 | Joined: 24th Feb 2006 | Posts: 266

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On my recent lightsaber duel, I found a new way to do just what you're asking. Use neon objects with size and spread set to 0 and make all colors white. Also make the feather 0. You can then use this to generate a white matte for your footage. Also, you can use multiple masks to create complex shapes instead of one big mask for the whole thing. This also gives you better control because then you can add a directional blur grade to correctly match motion blur in the footage, and other grading filters to matche other properties of the original footage. You can then render just this layer and use it as an object mask on your footage later.

You can also do the same, but make everything black and set it to 'Multiply' in the blending options. This can be used to cut out objects infront of what you want to extract.

I might make a tutorial to make this easier to understand, but that's a reasonably sized might.