Green Screen On Ice
Published : 13th March 2007
No it's not an upcoming Christmas time figure skating show.
Rather an upcoming job where a skater is shot head to toe, actually skating some, against green (about 30-40 wide) on ice of course.
I have done a lot of FX/Green screen work lately but this one an interesting challenge. Considering the ice will act as a mirror. The green can only be 15-20 feet from the skater as the CG background has to look as if about that distance from him.
A few things that cross my mind :
A heavy-duty polarizer is an idea to reduce green reflection but it doubt it will knock it all out. I can light the extra 1.6 stop easily.
Lighting the green just enough to get a good key is another way to reduce reflection level.
Another idea is to get a reflection so strong, keeping the ice slick and wet, that the entire image is keyed even the ice on the ground. Then just shoot some ice as a plate to key as floor.
Or perhaps, I have doubts about that one, just use very black as BG instead of green and try a luminance key. Will talk to post about that.
We are doing tests on Monday as I am not about to put my head on a log and go into this one blindly.
Any other thoughts...feel free to share.
Daniel Villeneuve, c.s.c.
Directeur-Photo / Director of Photography
Daniel Villeneuve, c.s.c. wrote :
>>Rather an upcoming job where a skater is shot head to toe, actually >>skating some, against green (about 30-40 wide) on ice of course.
I just worked on a job like this not too long ago. An animator we work with was doing a combo animation/ Live action thing. He needed a hockey player, skier and speed skater. For the hockey player and speedster shots he needed full body coming at camera, and shots from 3/4 above, straight overhead, and profile drive bys ( all full body ). He decided to place tracker ping pong balls painted blue on the ice ( 10 feet apart or so ), and created a "lane" for the skaters to move in. They hung a large white silk in the background and lit the hell out of the rink.
They mostly went for flat white light, and while I don't remember what they used, it wasn't a massive set up. I think it was maybe 4 20K's... can't say for sure. It helped that all the talent was to be wearing bright red lycra body suits.... it was a Canadian Olympic thing.
Anyway, the keys worked great, though there was clean-up for sure. He shot mostly 90 -120 fps and sped up to real time where he needed to. Skinny shutter as well ( don't know angle, but I'd guess 90 or 120 ). In transfer we went for hero images, but also did some flat passes for keys.
I'm not sure greenscreen would have been worth the hassle.
There's my tale from the front.
Chicago / Santa Monica
class="style2">>>Considering the ice will act as a mirror. The green can only be 15-20 >>feet from the skater ...
Usually it's a good idea to cover un-needed surface of the green screen with black if possible to cut down on contamination. In this case, it might be a good idea to cover any excess green with WHITE fabric (muslin?) so that the reflection is a bit more natural - less green on the ice to deal with.
Also, what about having the ice roughed up and NOT flooded to pristine gloss?
If it's even enough it might not be too bad - and they can always add CGI reflections.
I think it's pretty unlikely the Pola will help. Worth a try, though.
David Perrault, CSC
Daniel Villeneuve, c.s.c. wrote :
class="style2">>>I have done a lot of FX/Green screen work lately but this one an >>interesting challenge. Considering the ice will act as a mirror.
From my old days working with the NHL : Not as much as you think.
Freshly zamboni'ed ice will shine but after it dries ice is pretty dense and does not reflect much at all. In fact it's more like someone sprayed it with dulling spray. Slightly lower camera angles help too. White always beats out any colour (hence why it's so hard to repaint a wall white). Enough glow to cover any spill if you get any, will not take much.
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BlueSky Media, Inc.
I've never done this, but isn't the ice pretty dull/flat?
I would think that a little tilt on your screen and/or properly angled side lighting would help to keep the bounce off of the ice (?)
The pola will help as well.
ICG, New York
I've shot ice skating against green, with green under a layer of ice as well, and it worked remarkably well. Also, because the clear ice was shaved off into spray by the skate blades, it would transition from clear (with green behind it) to white. So the final composite had beautiful ice spraying off the blades, easy.
You also might consider a Scotchlite screen, and light it with a green ringlight to reduce green ice reflections. I've not used that trick myself, however.
Maybe keep the spill and use it to key a "reflection" of the CG background inverted onto the ice?
Fort Worth, TX
I'm not sure why the green screen on location has to be physically located the same distance from skater as the new BG will?
Is a reference point needed?? and if so why couldn't a 2 or 3 m "stick" be placed used and painted out later??
The green backing distance may well have more to do with frame width for skating and reflections on the ice than anything else
I would say bluescreen is a much better option.... ice tends to lean towards blueish and any small spill that you couldn’t suppress in post would look much more natural then green.
Also it is pretty easy to paint ice. Just like the blue/red lines on a hockey rink its very simple to paint the underside of the ice and lay a thin layer of ice top... then you have a full keyable skater, complete with reflections, shadows etc.
Lots of folks also don't realize that sometimes you don't need a 50 foot screen. If a skater is skating in an area ten feet wide but your shoot needs to be twenty feet wide (you are shooting off the screen but well out of safety of the person on the screen), all you need is a green screen behind the area the person skates. The rest can be easily matted later.
I don't think this is brain surgery having done a number of ice rink screens. The ice is really not that reflective once it is dry and frankly the screen doesn't need to be bright, just properly saturated for chroma so it need not cast lots of light.
BlueSky Media, Inc.
888.435.5428 ext 31
Offices in NYC and Amherst Mass.
I would recommend the Reflecmedia system. Basically a light grey fabric that has hundreds of thousands of glass micro-beads sewn into the fabric. You place a green or blue LED light ring around the lens and Voila! Instant perfect green/blue screen with NO lighting required for the screen.
Bogen in NY is the US distributor for the system. Works equally as well on film as video. I'm not sure who if anyone rents the system, but I'm sure Bogen can steer you in the right direction.
North American Camera, LLC