GreenScreen


#13

The last part. isn’t conufssing more. needs some time to process it correctly. lol i understand it basicly. but i’ll need to re-read a couple of to actualy get it correctly into my head.

thanks for all your help.


#14

Jasonsco is right. shooting green or blue screen with dv, or any format which captures at 4:1:1 creates problem after problem. The other year, for a uni assignment, we shot on greenscreen with a DV camera at 4:1:1, and good-luck keying it. We tried AE, Combustion, and DF and neither could key the green. We resorted to rotoing 750 frames! I dont know too much about camera, but if you an, try get your hands on a camera which outputs in a 4:2:2 format, or 4:2:0 as a bare minimum.


#15

so what exactly happened when u shot 4.1.1?

because my friend has recently did a test shot. and to be honest it didn’t work well. well the actualy removing of the green. it was all pixelated and jagged edges.

how do u get around this.


#16

Exactly that. It looks like rubbish. That’s why we roto’d 750 frames cause we couldn’t key it! 4:1:1 doesnt store as much colour information as 4:2:0 or 4:2:2; that’s why it basically impossible to shoot green-screen on miniDV cam-corders.


#17

I did a green screen project with Dvx100A edited in final cut pro with filter color smoothing 4:2:2 and exported to shake for smothing the jaked edges remember if you do a advanced 24p or 24p for action its not going to work out. Its easy.
I got better results. Its that we are not patient enough to read through the shake manual.
You should deinterlace, add color space change it from out rgb out yuv add a blur and add another colorspace change in rgb to in yuv. That’s it just in the blur properites change the x pixels so that the jaked edges smoothens out. After that you can use the xor node to use it as a wraper to have the background wrap around the edges of the foreground.


#18

We did some DV stuff (with some nicer DV cameras) back in 2000 and it was painful to say the least. We actually ended up using a static digital camera for shooting some background plates as opposed to filming them. Resulted in a lot of locked off shots, but the backgrounds had less issues. for the foregrounds, once you pull the key and garbage matte it, your biggest issues are going to be spill supprsession and the jaggies.

If you’re locked into the technology, you might consider one of the following approaches:

[ul]
[li]Make it all black and white as a stylistic element. This is more something to think about when shooting, but it can help cover up some of the spill issues.
[/li][li]give the whole thing a bit of blur/glow as a stylistic element. Make it almost dreamlike, again covers the crap. We did this for some scenes in my partner’s senior thesis back in 2000 that were just not keying well. Made it a dark smoky room basically. Worked great for a quick fix (since we couldn’t reshoot)
[/li][li]A lot of places will rent cameras at discounts to students, get a nicer DV cam (or HD even) and then work with that footage, even if your output is only NTSC or PAL
[/li][/ul]


#19

Getting nice keys from DV is very difficult, but not impossible. Here is a shot I composited a little over a year ago. I shot it on a Canon GL2.


#20

We meet again, Daniel-san. :slight_smile:

If you can plan your DV shot to have mostly dark subjects (dark hair & clothing) in front of a green screen (or bright/blond subjects in front of blue), you can use the color difference key to pull a quick core matte, then turn to a luma-based solution to bring out the edge details.

Basically, a color-only solution with a DV plate will be challenging at best, but that doesn’t mean you can’t get a good key from a greenscreen shot with DV.


#21

I actually captured that shot through a JVC Mini DV Professional Deck. When I inspected the color channels, they did not appear to exhibit the DV compression artifacts. Maybe the JVC deck does some sort of upsampling to the footage during capture. I don’t know.

But anyway, it allowed me to keep the fine hair detail in the composite above.


#22

The color compression would still be there, but it wouldn’t have much impact on a shot like this where you have dark hair in front of a green screen. This is the fundamental recipe for an easy DV key: Dark subject in front of green. The overall luma contrast is carried through to the RGB channels, so the color difference keying calculation picks it up quite cleanly.

If your subject had blond hair, this same setup would have been much more challenging to key.


#23

I recently had a project, keying on miniDV. The result is quite bad, and my company ends up buying 3rd party keying program which manage to get quite a decent matte.

Bottom line, miniDV is a no no. You surely end up doing rotoscoping which is tedious.


#24

So here’s kind of a what if to spark a little more discussion. It sounds like you’re suggesting green for the dark fg subject, perhaps because of the contract of dark on the brighter green. Yes, no? So for your blond haired subject, would it perhaps be best to have a darker blue backing?


#25

The technique that I’ve heard used most often is that you blur the UV channels (the chromanance part of the YUV) then mix that back in with the Y (luminance) and your ready to pull a matte. Do just enough blur so the pixelated jagged edges soften. Use that only for pulling the matte. Once you’ve got your matte, go back and use the original footage for applying the matte.


#26

Although a week ago i’d have told you the same as everyone above, but just a couple of days ago i found MiniDV chroma “Holy Grail”

It’s called DVMatte Pro:

http://www.dvgarage.com/prod/prod.php?prod=dvmatteae&sub=features

I couldn’t believe my eyes when i saw what it could do. I shot myself against a green cloth that wasn’t very well lit (it had also plenty of creases), i played around a bit with the plugin and that was it. Perfect.

Try it. It’s great for those like me who don’t have more than a miniDV cam and still want to make digital fx.

There’re also two other answers to DV keying. They’re called Chromanator and Serious Magic Ultra Key. The last one has something called “vector keying”, specifically created for DV.


#27

As far as I know DV Matte Pro uses that exact technique. Not that it’s expensive, but if you have a decent comping application, you can do it yourself easily.


#28

Drop by your neighborhood photography and lighting store. They’ll often sell large green screen sheets which you can use to fashion into a green screen, they’re also really good for backlighting.

If your friend is planning on using a greenscreen but not spending the time and $$ to setup a nice evenly lit screen and is using a DV camera, he should be aware he’s going to be spending weeks doing tedius roto work. Like other here, I’ve spent endless hours rotoscoping thousands of frames because of poor screen lighting and craptastic compression.

If anybody has any doubt about the validity of using Green for DV though, load up some DV footage into a compositing package and extract each RGB challen individually. The blue is useless, the Red is pretty good and the Green is by far the least artifacted of the bunch.


#29

Me and a few friends purchased a color called “Reptar Green” from LOWES. It keys really well.


#30

Which is exactly why green will be a major pain to key for a blond subject, since the green channel value of the hair and screen are the same high value, and you’ll be left with keying off the blue and red. :stuck_out_tongue:

Yes to both. :slight_smile:


#31

DV pro matte looks good :o must try it


#32

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.