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Monday, November 03, 2008

Filed under: CamerasPost ProductionProductionTraining

The RED Camera and Green Screen

Art Adams | 11/03

What you need to know before you learn the hard way

I’ve heard that the RED is the greatest tool in the world for capturing green screen footage. I’ve also heard it is the most awful tool imaginable for any sort of compositing. It’s a bit difficult to come to any sort of conclusion based on such information.

Fortunately I’ve been able to pick the brain of my friend and long-time DIT Jay Farrington, now a partner in the San Francisco Bay Area camera rental house Chater Camera. Early on he told me of a feature film test that had used an early build of the RED camera to shoot blue screen, and they’d had horrible luck with tungsten light before they switched to HMI’s. After that everything went swimmingly. “Hmmm,” I thought, “My tests have shown me that the RED camera likes daylight more than tungsten… maybe I’m on to something here.”

More recently Jay told me that he’d heard tell of a number of green screen shoots that had used the RED with great success. And while there were some who lit their green screens with straight tungsten light and left the RED unfiltered, others were gelling their lights or using blue filtration on the lens. The most often used filter, he said, was the 80D.

My handy ASC manual (eighth edition--it must be old because it still has film cameras in it) told me that the 80D was half the correction of an 80A filter (which converts 3200k tungsten light to 5600k daylight as a loss of two stops) and only cost 1/3 stop of light loss. Further research on the Internet showed that others considered it to cost 1/2 stop of light loss. “Hmmm,” thought I, “I’m sure I can afford a half stop of light loss on a stage. This is worth testing.”

During the test my Sekonic L-558C meter told me that the 80D filter actually cost 2/3 stop, and as I rate the RED at EI 160 in order to maximize use of the high-end of the sensor I found myself working at an effective EI of 100. “Hmmm,” I thought, “not so much different from an F900 with a Pro35 adapter. I can make this work.”

Then I found out about the teleprompter…

Teleprompters cut about 2/3 stop of light, so in the end my effective EI was around EI 40. Two bounced Maxibrutes later I found myself able to shoot at a T2. I haven’t done that with 35mm lenses on a green screen stage before, but it all worked out fine.

We shot several tests, but here are the two shots that were most informative: one shot under tungsten light with no filter at EI 160, and one shot with an 80D half-blue filter at EI 100. (I adjusted the RED’s white balance preset to 4300k in order to compensate for the blue of the filter.) The tests were done without shooting through the teleprompter.

The first thing I learned was that if you ask for an “80D filter” without enunciating properly you’re likely to end up being handed a bottle of Ritulin. The second thing I learned was that the 80D filter helps considerably. Turn the page for more…

(Page 2 of 4 pages for this article  <  1 2 3 4 >)

               



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Did you place the 80D filter on the camera or on the light source?

I’ve often seen the green screen lit with one set of instruments and the talent lit with another. If the green screen is lit so it’s instruments do not spill onto the talent, would you then light with green on the screen and white light on the talent?

Peace,

Rob:-]

Posted by Rob  on  11/05  at  11:46 AM


You said, “… the 80D was half the correction of an 80D filter ...”. Is there a typo in here?

Peace,

Rob:-]

Posted by Rob  on  11/05  at  11:47 AM


Please clarify a couple of points:

When you say “full body shots” are you referring to the seeing of skin tones on your subject ? Is that your concern ?

If that is the case then why not just make sure that there is no contamination of the subject by the light illuminating the
Green screen ?  Would using Super Green Kinos or a Lee green on your tungsten lights significantly improve the key ability of the screen ?

I have lit hundreds of green screens for films, Keeping green
contamination off the foreground subjects is simply a matter of light control and having a large enough space/greenscreen to
keep the subject far enough away from the screen to make sure
that there is no bounce spill.
I would light the green screen to its best keyablity and then light the subject to the proper ratio of screen to subject in terms
of over/under stop wise.
I would much prefer to gel my lights than to filter my lens because when I filter my lens I am affecting not just the green screen but also my subject.

Perhaps I am misunderstanding , again my experience is primarily with film. We are starting to be questioned about whether the RED is a viable option for some of our work.
thanks-J

Posted by  on  11/15  at  09:47 AM


Great article Art!

Posted by  on  11/22  at  03:40 PM


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