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Old January 24th, 2002, 12:47 PM   #1
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Blue screen or Green screen

The heading says it all.

A part from making sure that the subject matter does not contain the same colour as the background;

Is there a difference between them (apart from colour)?

Is one better than the other?

Is one used more in Film than Television?

What is the best way to light a blue or green screen?

So many questions, I hope they could be answered,

Ed Smith
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Old January 24th, 2002, 04:35 PM   #2
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>>>What is the best way to light a blue or green screen? <<<

The "key" in Chromakey is to light evenly--no shadows or "hot spots"... so soft lighting ideally. Ross Lowel talks at length about soft light sources in "Matters of Light and Depth"

If you wind up with ugly artifacts in your blue/green screen then you'll have to use the "garbage matte" tool in FCP but now we're talking time and effort.
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Old January 25th, 2002, 04:05 AM   #3
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Mike,

Is that a book your mentioning or something else?

Ed,

Besides green and blue there is also orange and
perhaps some other colours. It mostly depends on
what colours are in your "objects" or people that
you are shooting. Blue is the furthest away from
human skin tones, so that's why you see that
a lot used. If you have blue clothing or dark reflective
colours (which can sometimes look like blue) it might
be best to go with a green screen.

Now with DV I thought one colour was also assigned
more bits (or less compressed, which ever you want
to call it). I'm thinking it is green, but I am not sure.
If it is green, it might be wise to use green screen
for better green quality when you get to the computer
stage to remove it. Maybe some testing is in order
here. Small portable screens are easily and not
very expensively rent! You can even buy screens
that are blue on one side and green on the other.
This way you can test before you buy. Or perhaps
just rent the screen for the days you need it!

Good luck.
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Old January 25th, 2002, 09:18 AM   #4
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Ed here is a link i found it might be of use to you
http://www.seanet.com/Users/bradford/bluscrn.html
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Old January 25th, 2002, 10:46 AM   #5
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Yep, it's a book. $28.95 on amazon.com--once in a while you see it on half.com--it's a great book for all types of photo, cinema & video lighting--he treats it as an art form and it's quite fun to read (not some dry technical text).

Matters of Light & Depth
by Ross Lowell
Paperback - 224 pages (April 1, 1999)
Lowel-Light Manufacturing, Inc.; ISBN: 0966250400 ; Dimensions (in inches): 0.53 x 8.96 x 9.00
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Old January 25th, 2002, 12:43 PM   #6
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Cheers guys for all the responses, they will help greatfully.

It was just curiosity which made me pose the question, plus I have been using an old red blanket to shoot anything which needed chromakeying.

I think in the coming monthes I will invest in a proper screen (probably blue...or... possibly green!).

Thanks again, all the best,

Ed Smith
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Old January 25th, 2002, 04:42 PM   #7
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that's an awesome link, Ian! They raise an interesting point about the risk of light spill on the subject from the green being more objectionable than blue spill.

I like where they say the trick is in lighting the foreground without screwing up the background.

Lots of good info there.
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Old February 8th, 2003, 08:00 AM   #8
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green screen dance floor

Heya all,

Here is prob the most peculiar question you have been asked, but why not. I want to work a way out of doing a green screen effect on a dance floor, as in the floor being a green screen and people dancing on it, but making the floor look all wild.

Now i am not sure how to light it, i may have to build something and light it from underneath but i am not sure...


Anyways, lets get the brains tinkering, as i am totally new to green screening, production and post.

Thanks all,

Zac
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Old February 8th, 2003, 09:17 AM   #9
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What angle(s) will you be shooting the people dancing from? Straight on or from above?

- don
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Old February 8th, 2003, 10:48 AM   #10
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That's going to be tricky to light, as the shadows cast all over the floor will mess up the green screen effect. I'd light the people, low, from the side, and if the budget allows, build a fake floor and light it from underneath. Sounds like quite a project, let us know how it works out!
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Old February 8th, 2003, 12:51 PM   #11
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They'll have to dance in their socks.
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Old February 8th, 2003, 02:35 PM   #12
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I wish you luck.

I would try lighting from beside the camera at all times, that way the shadows would be behind the cast. It still wouldn't be perfect, but it's the cheapest and best way I can think of.

-Nori
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Old February 8th, 2003, 03:13 PM   #13
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If you use keying software such as Ultimatte, you can deal with the shadows OK. The problem is that the dancers are going to be moving around closer and further away from the lights, and there's no way to light the background separately from the people. If you just light the whole thing with soft lights, you might be able to get something out of it. What you need is a floor made out of opal glass that you can light from underneath with green-gelled lights. I bet that would cost a fortune.
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Old February 9th, 2003, 02:44 PM   #14
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Just so you know, to get good results this isn't going to be cheap.

I would use lots of either softboxes, florescent fixtures or pancake lanterns.

Flourescents maybe the least expensive per instrument, BUT, here's an example: http://www.kinoflo.com/product/blue%20and%20green%20screen/bluegreenscreen.html
of how they light a large green screen wall. DOZENS of instruments.

You'll need less softboxes or lanterns. I really like the lowell Rifa-88 w/ 1000W lamp.

Could you do it outside?
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Old February 10th, 2003, 02:21 AM   #15
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Yes. i would not light it from beneath. Mainly because you would then most probably get a bad green hue to the dancers. Something that unless you are shooting on film would be very tricky to key out properly. You want high contrast between your foreground and the greenscreen, and the less material you have to do this difference with (ie. resolution) the more careful you should be.

Now, people would argue that "hey, i can green screen perfectly with my DV camera" and i do not argue here. But to greenscreen from a wideshot is a whooooooooole lot different than greenscreening a closeup.

My suggestion would be to if at all possible, build the floor as it should appear in the video, then use greenscreen for the surroundings.
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