How did they make this effect on face?

[hello0]

https://www.youtube.com/watch?v=NO94MYyc7SE

in second 0.08 where they projected a different video onto her face?

[jagabo]

It looks to me like they just did an overlay with an alpha mask based on brightness. An example from a few seconds later in the clip:

Original, alternate
mask, overlay:

[hello0]

Can i make this effect even if it is not bright? Like applying this effect on my pants only?

[jagabo]

Can i make this effect even if it is not bright? Like applying this effect on my pants only?

It depends. You might be able to use the hue of your pants if they are different than the rest of the frame. For example, wear bright green pants then make green transparent, and make sure there's nothing else in the frame that's a similar shade of green. This is called chromakey. It's how most such shots are done (though usually to make the background transparent). If you've already shot the video and there's no distinguishing quality of the pants you can use to create an alpha channel it's much harder and will require a lot of manual work (though editors often have tools that help you track motion).

[pandy]

You can use chroma key if pants are more or less solid color (color should be unique - thats why in past they used something called blue box now usually it is green box) - in this pictures Debbie is shot on dark background and easy to threshold brighter than part (ordinary analog comparator i think) - later black&white is used as mask and some edge detection is applied to it (analog differentiator), edge detected are used to switch between two sources (some analog multiplexer/switch) that's how it was done probably in those times.
In digital world it can be done slightly different chroma (luminance) key used to produce alpha channel and later reapply edge mask to emphasize transition.
Probably such task easy to do in decent NLE but also i can imagine Avisynth or ffmpeg as sufficient to do such processing.

[hello0]

I made a testvideo, I recorded my hand in front of a white background, in my VE I used Background-remover and underlayed a different video as mask.
I then used the color orange or so to make the hand transparent and it worked.

How do I make the video black-white like you did with Debbies face? I could not find a Filter.

[jagabo]

How do I make the video black-white like you did with Debbies face? I could not find a Filter.

I used an AviSynth filter called mt_binarize(). It makes all pixels darker than a threshold black, all pixels brighter than the threshold white. But you can achieve a similar effect with brightness/contrast filters plus a greyscale filter.

[hello0]

I found one filter in my VE

[hello0]

https://www.youtube.com/watch?v=O0zeuzYHYKM

I have a new question, how can I make the transition from normal to black/white like in minute 4:13?

My VE can do it, but there is no smooth transition, even if I use transparence.

[Brainiac]

Cut the video so that the black and white portion is isolated and use a cross dissolve transition at the cut (edit point).

[jagabo]

Create an overlapping B/W clip, then Dissolve() (crossfade). Dissolve from frames 30 to 60 in AviSynth:

WhateverSource()
p1 = Trim(0,59)
p2 = Trim(30,100).mt_binarize(100, chroma="128")
Dissolve(p1,p2,30)

[johnmeyer]

The Blondie effect was done on the luma, using the studio switcher. It was all done in analog.

If you have the proper tools, you can create your own luma mask and do things that are identical to a green screen.

For instance, over a decade ago, when America Idol was first on air, a friend of mine wanted to sing happy birthday to his wife, but as an American Idol contestant. He sent to me some video he took of himself singing, shot on a tripod against a stationary backdrop indoors. He started the camera, walked into frame, and did his shtick. Neither the camera, the background, nor the lighting changed.

That last sentence is really important.

I then created a mask of the background, before he entered the frame, and used that to create a difference mask. Any pixel that was brighter or dimmer than the original pixel was replaced with a static shot I got of an empty American Idol set (I just Photoshopped out the singer that was there) and dropped that into the background. I then intercut him with some video on a DVD of the first AI season that he sent to me along with his tape.

This is the result (saved as a 7MB WMV video because that was all I had back when I did this):

Faux American Idol Contestant

.

[jagabo]

He sent to me some video he took of himself singing, shot on a tripod against a stationary backdrop indoors. He started the camera, walked into frame, and did his shtick. Neither the camera, the background, nor the lighting changed.

I then created a mask of the background, before he entered the frame, and used that to create a difference mask. Any pixel that was brighter or dimmer than the original pixel was replaced with a static shot

I used to do that with live webcam video many years ago. The mask was also used for collision detection (so the person could interact with computer generated objects). One day the webcam background started appearing unexpectedly. And game objects started colliding with the now visible background. I kept looking through the code trying to find the bug. Eventually I realized that the room was partially lit by sunlight and it was a partly cloudy day. As the sunlight changed with the clouds the lighting in the room changed enough for the background to become visible!

[johnmeyer]

I first learned about this idea when I did consulting work for Reality Fusion, a Santa Cruz startup, back in 1998. They had a demo, which for its day, was spectacular, and it involved compositing yourself into a game, based on having a constant, unchanging background (no partly cloudy days allowed!). They were declared a "demo god" at the big venture capital conference in Las Vegas, Demo'98. This is the NY Times account of the event. Search for "Reality Fusion."

https://www.nytimes.com/1998/02/10/science/personal-computers-waiting-for-the-big-one-...d-waiting.html