Green screen in DV question

Denis Haineault

Denis Haineault

Well-known member
Hi,

I'm completely new to the world of film making/editting/etc... and have been reading on this forum for about 1 month now. The plan right now if to acquire a DVX100B and Final Cut Studio...very shortly.

Anyway, I came across a post recently which mentioned that there's some green bleed that always seem to occur with DV compression...I was not aware of that.

My questions:
- How is this usually handled?
- Can a different compression be used when capturing to correct/minimize the problem?
- Or is it more a case of what software you're using for chroma keying?
- I assume getting an HDV camera like the HVX would produce better results...is this correct?

Sorry for all the questions, but I'd just like to know what to expect as I'm getting ready for my new hobby :)

thanks in advance
 
thats a problem with the resolution of the SD camera. If you want to do green screening, go HD unless you light extremely extremely well. even then its all up to what the pixels can pick up.
 
Main problem is 4:2:2 color sampling. This makes the color resoultion about half of lumi resolution. Thsi combined with compression makes DV tough to pull mattes,
HVX is higher res but has some similar color resolution issues.

There are some specialty plugins that can help reduce the problems.
DVGarage has one among other vendors.
 
anyways, i should try to do a green screen test with the DVX. What is the most important? Lighting the background or the subject? Backlight?
 
The DVX comes with a marker that helps identify low light areas on a green screen.
 
PaPa said:
anyways, i should try to do a green screen test with the DVX. What is the most important? Lighting the background or the subject? Backlight?
Click to expand...

Lighting the screen EVENLY is key. Try to get it all lit the same amount, no hotspots or low points. This is critical. Having a backlight on your subject is nice as it helps to separate the subject and define those edges. Also, it is very important to keep some distance between your subject and your screen in order to avoid green spill. You can pull decent keys from DV footage, depending on the software you use. Having progressive footage from the DVX helps. If you use Vegas then try applying a chroma blur (just a slight one, there are threads about this in the Vegas section) as it will ease some of those jagged DV edges from a chroma level and make the key easier. I've gotten good keys using Vegas' simple tools, but you can also step it up and use more advanced tools like After Effects and many advanced 3rd party plugins. Don't be too discouraged, you can make things look good but it takes time, effort and understanding of the principles involved. Best of luck and let us know how it turns out.

Also, just a few minor corrections. I think Scotty meant 4:1:1 color sampling, as opposed to 4:2:2. DV is 4:1:1, as 4:2:2 is usually an HD sampling range. And just as an FYI sined, calling the HVX an HDV camera will likely result in hanging you up by your toenails in the future. But since you're new we'll let it slide. :thumbsup:
 
Shoot progressive. Put at least 10-20 feet between your subject and the screen. Light the screen evenly. Put a backlight on the subject with a magenta gel. If your subject has very light/blonde hair, you may want to underexpose the screen by a stop or so. Get dvMatte Pro (already mentioned) - it will drastically improve your quality of key. Get a good read off the screen with a waveform monitor, if you have the chance, and adjust your camera colors until they're as close to true green as you can get.

All that advice is if you are unable to follow this first piece of advice: don't shoot DV. Pretty much any other format in existence will give you better chroma keys. DVCPro, HDV, Beta/Digibeta, whatever. Actually, all that advice still applies, but you can get away with a lot more in any other format.

In the end, don't expect perfect keys. But it can be done acceptably well as long as you follow the advice above.
 
ovjamaica,
Yeah I remember reading an article about proper lighting, distance, magenta light, etc... for better green screen results, but I guess the way I interpreted the "green bleed" post was that this problem will happen regardless. You mentioned Vegas, but I will likely stick with Final Cut, so I guess I'll find out soon enough what I can get away with, unless you can comment on FCP? --- BTW, I keep my toenails very short, so I guess I'll be safe for now for the hanging part ;) ...but I stand corrected.


dougspice,
You say "don't shoot DV"...would I have this option with the DVX100B ? I was under the impression that this is the way the camera records...period. Or would the solution be to record "live" with NLE software and tell it to record "as is"?

thank you all again
 
sined13 said:
You say "don't shoot DV"...would I have this option with the DVX100B ?
Click to expand...

No. It doesn't matter the DVX version all capture in DV.

I would suggest that you have a blue screen too; with Blonde or light hair people, I found the blue screen work bests. But as everyone mentioned the key is the lighting of the background and distance of the subject to the background.

I've heard nice things about DVmatte Pro; but as mentioned AE (what I use) w/ Keylight is sweet. It will take some time to pull a nice key - no doubt - i'm now working on converting 30 GS vids all shot with the 100a and I'm using Keylight.
 
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