Blue Screen Question

[dmccoy]

I realize this shows the inherent shallowness of my character but-
How do you get bluescreen to work? I have tried what I thought were relatively blue bed sheets and tarps but when run through FCP's Blue/Green screen filter nothing much happens. Even when you manually key it you seem to get poor results. Is this a special kind of fabric people use? My camera is a low level consumer miniDV cam.

Thanks but very confused. (NOTE: I blasted most of these with pretty strong lamps too.)

[richard.fisher]

I've used adobe, as oppossed to FCP, and in my experience, the problem seems to be that it is difficult to get a uniform blue behind your foregorund actors (or props or whatever). I've tried blue bed sheets but they have always had folds or crinkles in them. You can change the settings, so that it broadens what bit of the image the program will filter out, but then you start to lose bits of image you had previously wanted.

I use the blue screen key often for very small effects (such as putting a title sequence togehter) but find I don't have the exxpertise or time for anything too ambitious.

As is often the way here, rather than directly answering your question, I'll ask is blue screen actually the best way to achieve the effect you want (it may well be). Let us know what you are trying to achieve, and we might have some alternative suggestions on things you might like to try.

[Matty2phatty]

There is actually a certain colour blue or green that you're supposed to have, though it doesn't REALLY matter.

The problem usually with low budget gear is that DV and HDV cameras compress the image, and so you end up with 'near blue' and 'near green' with lots of grain and artifacts all through it.

The computer can't read it as a solid colour and so you end up with a dodgy image. Another factor is that you're using consumer editing software to pull off the effect.

High end compositing gear like Flame or something are a lot more customisable as far as which colour spectrum you want chroma keyed out.

If you go to a professional lighting place they should be able to assist you as well, as the place near me was able to sell me large sheets of the right coloured stuff, and advise me on how to light it consistantly.

[dmccoy]

Sorry, my internet cut out for a week there. Thanks for all the advice guys. I will definetly give those a try. [img]graemlins/thumbs_up.gif[/img]

[sn-films]

If you are looking for info on how to light a blue/green screen, these guys have a great DVD that includes some tips on how to light it. They have a sample on the site you can preview.

http://www.dvcreators.net/products/d...ghtenment.html


As for the actual backgrounds, you can pick those up from a couple places. B&H has been one of my favorites for a while.

http://www.bhphotovideo.com/bnh/cont...rch&Q=&ci=6446


Something else I've noticed is that I've had more success creating a seperate matte video and use that to control the overlay rather than key out the actual color. To do this, first shoot your clip. This shot uses a sheet that in no way resembles true chromakey blue.

ORIGINAL IMAGE

I'm not sure what toolset FCP offers, but a MediaStudio Pro user wrote a plugin that really helps develop mattes. Mathematically, it subtracts the red and green RGB values from blue, and then reassigns the resulting value to the overall luminence channel, giving you a black and white matte based on the original clip.

MATTE


Then, use the luminance from your matte to control what areas get keyed out. You'll need to tweak the controls to get the desired results, but like I said I've gotten much better results doing this instead of keying out a clip directly.

KEYED IMAGE

Good luck!