Masking using Multiply mode

[Stephen Mann]

Compositing modes are pretty standard and work the same in every editing program I’ve used. I am not familiar with the “fill behind” feature in Photoshop, but it could be an additional compositing feature unique to Photoshop. Can you use Photoshop to mock up a sample of what you want to do in Vegas.

Steve Mann
MannMade Digital Video
http://www.mmdv.com

[Daniel Hart]

Hmm. Multiply in Vegas definitely works differently to Vegas.

Here is what I mean.

https://www.djh-graphics.com/modes.jpg

TOP – my video with new clip on top – obviously, regular source alpha mode, where it blocks everything underneath it.

MIDDLE – same layer, but with Multiply compositing mode. Fine where the “solid” video goes, but for some reason totally black everywhere else.

BOTTOM – How I actually want it, with the right figure overlaid on top of all the other video showing all underneath.

Hope that’s clear! Thanks for trying to help…

[Daniel Hart]

BTW – ignore figure on left. That was a green-screen filming, chroma-keyed out with the body copletely silhouetted out. I don’t want to do anything like chromakeying with the one on right, just to plonk it on top of everything else, as the clash of elements (and having it pushed down in the visual mix) is what I want to achieve!

Besides, it was filmed on a white background so that would be pretty difficult!

[Stephen Mann]

I think it’s working exactly right. Everything outside of the image of the girl with the guitar is black. It’s multiplying the left side by zero. Nothing there. Black. Multiply any image with black and you will get – black.

You may have to make an intermediate of the girl standing and expand the background to fill the frame.

Steve Mann
MannMade Digital Video
http://www.mmdv.com

[Daniel Hart]

Gah – ok. My point is that Multiply behaves differently in Photoshop. And you can see what I am trying to achieve. Imagine this in PS –

1) document 1920×768, background image fills document, photo of whatever – a field.

2) layer above it, only a small square, the rest transparent – layer set to Multiply mode.

So it’s just like putting a sheet of acetate onto a photo – doubling up the image where it counts but NOT adding black wherever it is transparent! Anyway – I’ve been trying all sorts with Masking – am pretty certain this is the key to the solution. Whatever that is..

[John Rofrano]

[Daniel Hart] “doubling up the image where it counts but NOT adding black wherever it is transparent! Anyway – I’ve been trying all sorts with Masking – am pretty certain this is the key to the solution. “

Stephen already explained it but I’ll try and explain it again a little different. Vegas is not Photoshop. Any part of the frame that does not have a video image is interpreted as Black when masking (i.e., masks have no concept of “transparent”. Only black, white, and shades of grey). Any color Multiplied with Black will give you Black (so Transparent = Black mask as you have seen). The reason you have black edges is because the girl doesn’t fill the frame.

The solution is simple. Precompose the girl with a White background. The way that you precompose in Vegas is with Nested projects. Start a new project. put the girl on the top track. Place a piece of White Solid Generated Media on the track below the girl for the same duration as the girl. Save this project and drop it into the timeline of your existing project and use Multiply (Mask). That’s the effect you are after.

You see… a “mask” needs to always match the entire frame or else the missing areas will be interpreted as a “black” mask and black doesn’t let any color through (white does).

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Jery Ervin]

Hi, Dan,
A simple fix is to use an Event Pan/Crop Mask on the event that is being multiplied. To do that, select the event to be multiplied, go to its Event Pan/Crop panel & look at the timeline in the panel. There should be a checkbox to the left of the work “Mask” under “Position.”

Check that box & then use the tools that appear on the left margin of the Event Pan/Crop panel to click on the frame to create a rectangle around the part of the frame that you want to appear in your composited frame. The tools are similar in function to pen tools in Photoshop.

The key to understanding the behavior that you are seeing is the subject of transparency of pixels/parts of images.

In Photoshop, the multiplied pixels that are over the parts of the image that appear from the lower layers are transparent (or, could be pure white). Transparent (or pure white) pixels, when multiplied, have no effect on the layers below.

In Vegas, “empty” pixels are not transparent, they are actually black. As in Photoshop, black pixels, when multiplied, completely block the pixels in tracks (analogous to Photoshop’s layers) below the multiply track. The result is as you see in your tests.

Regarding transparency in video images, certain video formats support the idea of an alpha channel/layer, which could be used to cause the behavior you desire. The Event Pan/Crop Mask technique is simple and effective and, I think, will do what you want.