HDV & Green Screen

[ntbullock]

http://www.sequentialpictures.com/temp/ ... test_1.mov

After doing a lot of reading, I did a quick test of the key-ability of HDV. It's not bad if you actually capture full HDV and then down-res it to SD. My lighting was subpar [ie background @ about 30-40 IRE], but you can tell from this video that the edges are decent. I didn't spend a lot of time on it and it's not perfect, but I'm going to do another test with more lights. I had enough hurdles this go 'round. The key was done in AE using Keylight.

DV has a 4:1:1 color sampling, which isn't good for keying [watch SWE3: A Lost Hope]. The SONY Z1U has a 4:2:0 sampling rate which is better in some ways, but still not better suited than 4:2:2 for keying. All that information it throws away for compression-to-tape is good stuff for keying.

I'm not looking to do a lot of "screen" work, but I want to know what I can get away with using HDV. I was recently looking at the newly priced Shake software, which prompted all this. It has a version of Keylight and Primatte, which key totally different from one another. I really want to know if I can get away with some semblance of broadcast-worthy keyed footage with these elements.

[grizzly69]

I think it looks quite good. If you tweeked it a bit I think it would be broadcast worthy. I've seen worse keying work in some "made for SciFi channel" movies. Of course your subject (you) was an easier key than someone with frizzy or long hair. Or things that have some transparency. I suppose that would be further testing.

In my book it is much better than acceptable. But if you want Shake you'll find reasons to get it.

[ntbullock]

I'm gonna do another test very soon. Seeing what Primatte can do alone makes me want Shake. It's an interesting plugin. Shake is pretty complex to me. It's a different way of thinking. I see endless potential, though.

[tyrel68]

I may sound like a dink but what is "keying"?

[willekers]

Looks good, the edges are nice, they don't have any visible colour from the screen from what i noticed any way, of course i didn't analyse it frame by frame though.

What is hdv anyway? is it high-definition video or something like that?

[willekers]

Oh and of course, like you said, it isn't perfect and you could spend time colour matching it to the background and things like that. However even after that i still think i would have a real hard time believing it due to that fact that it is a video of your severed upper body floating through the sky...

[ntbullock]

http://www.sequentialpictures.com/temp/ ... test_2.mov

The screen was better lit here. I still did a REALLY quick key [removing the green background] on the HDV [high-definition video] footage. I really didn't light him well, either. It's just a test. I'd say that keyed HDV footage can look better than regular DV when it's scaled down to SD. I was a little surprised for some reason.

[grizzly69]

If you can get results this good with a quick key, then I think you can use the software you currently have.

You are aware the aspect ratio of your subject is off a little.

[Martian]

Tyrel read this;
Key Color Transition:
The Key Color Transition provides four types of transitions corresponding to the four key types.
1. Chroma Key Color: Chroma Key is keying by the Red, Green and Blue composition of a color. Use this key to make uniform background colors transparent.
2. Non Red Key: Non Red Key makes blue and green colors of the overlay images / videos transparent.
3. Luminance Key: Luminance Key is keying based on luminosity of an image. This key type alters the intensity of light gradually over time. At 0 unit luminosity, black color gradually turns bright while at 50 unit luminosity, 50% gray color gradually turns bright.
4. Hue Key: Hue of an image is the color produced by visible light. The common color terms such as green, red or orange refer to hue. The key type alters hue over time.
++++++
I'm no expert but I think the tests were pretty good, Could you do a test with something frizzy and faster moving? Maybe a girl with long hair dancing in front of a green screen.
++++++
Should we write what we think you and Anthony W were saying?

[ntbullock]

I wasn't worried about the aspect here. I just wanted to key something quickly to gauge the quality. I don't think a project at the moment would make me care about individual, frizzy hairs. I do, however, try to shoot at a higher shutter speed to minimize motion blur [which you can always add after the fact if needs be]. I shot myself with minimal lighting and used a shutter speed of 125, which is a normal speed but I wanted to use higher. With Anthony I used 180, but I had more light. I'd like to use at least 200 if I'm shooting action, though. The higher you go the more lights you need and the hotter it gets!

I may be shooting a fake self-help commercial this weekend in front of the greenscreen at my place. It's just for shits & giggles - oh, and learning. If it comes out decent I'll post it as another SEQUENTIAL PICTURES PRODUCTION!

[tyrel68]

Ok Question that seems just the same quality as Lost hope...whats the payoff? or am i just missing it totally.

[ntbullock]

It's slightly better. Also, it took MUCH longer to get the SW footage to resemble this footage. I'm not saying it's leaps and bounds - just a little better.

EDIT: To prove my point look at the two images below. Originally, I captured the first test's footage in both DV and HDV formats [DV being 720x480 & HDV being 1440x1080]. The HDV footage resized down to SD produces better results. Notice especially the edges on the left thumb, the right side of the face, and the right side of the right hand. Red doesn't compress well in these formats - hell, just look what happens to most reds in a jpeg image. You will notice more muddy stair-stepping in the DV footage. You will also notice if you enlarge the images that, my face for instance, is softer in the DV footage than in the HDV footage. I thought that was interesting, too. These images are straight out of FCP's timeline using BMP then cropped and jpegged using only a compression value of 2. Hopefully, this will be useful to someone.

http://www.sequentialpictures.com/forum ... een_dv.jpg

http://www.sequentialpictures.com/forum ... en_hdv.jpg

[tyrel68]

Well I can't deny the HDV does appear better :D

[xbay]

excellent key for just a quick test

[ntbullock]

We shot the commercial over the weekend [entitled: Back 2 Happiness]. It should be about a minute or so. Everything was against the green screen. I should've snapped some pics, but I wasn't thinking about it. I was using my smaller fold-up green-on-one-side-blue-on-the-other screen from amvona.com. This time I used even more light so I could bump the shutter speed up to 250 [I think it was]. That means there is less motion blur, and it's a little easier to key. After what I went through in post, I wish I had had more lights on SWE3 to shoot at higher speeds. This shoot went well though, and I used almost a full hour tape for this little commercial. Some of the lines are absolutely ridiculous.

Although this "small" project started out as a test, it's coming out well and I think there will be a decent level of quality. To me, HDV is keying much better than regular DV using Keylight.

[3DPiper]

Proper lighting is paramount.

Also, I rarely pull a single key.. I usually pull 3 or 4 to make proper keys that blend better with the background plate..

Plus, I always stay in full HD until the final render.. very important!

-Matthew

[Ensign Benson]

This time I used even more light so I could bump the shutter speed up to 250 [I think it was].

I know this is an old thread, but anyway...

How the heck do you shoot at 250 fps?
Is that when streaming direct to a hard drive cos I didn't think a computer/hard drive could capture so much data in real-time.

Man! you could totally do matrix slow-mo stuff with a cam like that.

[ntbullock]

Shutter speed - not frames per second. It'd be awesome to shoot at that frame rate, but sadly no.

[Ensign Benson]

Oh, that's interesting. I still don't get what U mean by shutter speed though. I thought the shutter of a movie cam always stays open, doesn't it? Or is it kinda like the exposure, the amout of light that gets recorded?

[ntbullock]

Exposure controls the iris. Shutter speed, I believe, you can only control on higher end camera. Usually you run it at around 125 shutter speed but you can lower it to allow more light. It affects motion so you have to be cautious of how much you push it in either direction.

[Ensign Benson]

That would explain it then as my cam isn't of the higher end. What type of cam do U use NT? I know i've read it somewhere but right now I can't remember.

[ntbullock]

SONY HDV Z1U

[Ensign Benson]

Cool. Do you happen to have any short test clips in full 1920×1080 resolution on the site anywhere?

[ntbullock]

I think it shoots at 1440x1080 res.

I had some footage for a little bit when I got it but not anymore, sorry.

[Ensign Benson]

Yeah, your right

HDV 1080i, like other new HD recording formats, uses a pixel aspect ratio of 1.33 to store data in a more mathematically and algorithmically efficient way. HDV 1080i uses a pixel resolution of 1440×1080, but when displayed is scaled to an aspect ratio of 1920×1080 = (1440 × 1.33)×1080.

From Wikipedia