Blue Screen Composites

Hammer wrote on 9/3/2003, 9:50 AM
Hello all, been a long time since I dropped by to check up on all the latest happenings. Anyway, I'm working on a little home project that requires some compositing. Basically I want to have my son dancing in one of his favorite videos. What I need are some tips on getting a clean blue screen without spending a bundle of cash. I have done some small experiments filming him against uniformly colored wall, and against a colored cloth. The cloth seemed to work better since there was more contrast. The real problem seems to be that either my subject stands out to much, or he gets overwhelmed by the back ground. Are there any cheap tricks you can pull with lighting, etc, to get better results? I'm still using vegas 3 btw.

Comments

Nat wrote on 9/3/2003, 11:24 AM
We are doing a green screen shot in my basement for a local film magazine.
We bought some green cloth from a local fabric store, paid 5$ for the meter which is very cheap. The important thing with some cloth is to get a fabric that is completely texture less, and that does not reflect light. If your shooting digital, light green is the best color. Now you need to make sure your fabric is uniform, so you need to use a domestic iron on it before the shoot.
Next important part is the lightning, we use 3 work lights that are placed between the subject and the screen, this way the talent doesn't cast shadows on the screen. An other little trick is to keep a good distance between your subject and the screen to avoid spilling.
Good luck !
ggp wrote on 9/4/2003, 10:15 PM
If you insist on using Blue Screen, put a 30 watt amber light as a backlight on the subject. This reduces the blue bleed on the subject. The further away from the background the better (no shadows). I use three umbrella lights way up high when I key. This puts the shadows down low and not on the back drop. The more organized the subject the better the key. For instance, if you have a lot of hair all frizzed out, this will not key well. Objects that are small, such as pens and pencils can be a problem with some backdrops. Keep the subject neat and dressed with a fine line and the key will be much better. Find a wall. Paint it green or blue and shoot!

Good Luck!
filmy wrote on 9/5/2003, 12:02 PM
If you don't want to spend much money people have had good results with going and getting green paper - like construction paper - and using that for the back. That would probably be the cheapest. Most of the 'real' stuff is expensive - paint runs around 30 bucks a gallon and goes up for the better stuff (Ultimatte paint between 50 - 65 dollars per gallon, DigiComp between 55 - 80 per gallon) Cloth is a bit cheaper but still can get expensive if you need a lot of it - Depending on what type and how much it goes from about 8 dollars a yard up to 46 a yard for Muslin. Also now there are specific colors for digital - "Digital Key Blue", "Digital Key Green" and "Digital Key Red" and they are a bit different that the normal Chroma key colors.

Overall lighting is the biggest issue. You need the back to be very uniform in the way it is lit and the subject needs to be lit in such a way as to not cause any shadows to fall on the backdrop. One thing that VV doesn't have is the ability to do garbage mattes, that would help in cases where the edges fall off or if you had shaows falling outside of the main area.

If you have a light meter it would be helpful because you could check to make sure what you have is uniform across the back.

This sounds like a lot - but you did say dancing was involved and that makes it more difficult. If it was a talking head you could just paste up green paper and probably get decent results. The second you add a lot of movement on with chroma key you can have a lot of issues if it isn't done correct. And, I'll say it again, lighting is the main problem. I helped out a friend of mine on a commerical shoot he was doing - he was the DP - and they rented out a stage with a cyclorama - green screen. They spent about 8 hours lighting it for the next day's shoot. I remember him bitching because it was harder to light the curves without getting bleed over from the sides. They did do it - just that is takes time to light.

Dunno if any of that helps or not. :(