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Old February 19th, 2008, 04:17 PM   #1
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OT- ChromaKey exposure

I have an interview to do and will use a chromakey BG [greenscreen] behind the subject, who will be lit in a controlled interior environment so all my exposure elements are under control.

It's been ages since I did a greenscreen and have forgotten about exposure of the screen.

Is it best to under or over expose the greenscreen in relationship to the subject's exposure. Thx
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Old February 20th, 2008, 02:27 AM   #2
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It is best to evenly expose the background and preferably get as much distance between the subject and the greenscreen.

Underexposing the background will more likely be somewhat uneven, overexposing it will wash out detail in the backround but you will have more green cast off on the subject which may result in a more difficult key.

So balance is everything... again ;)

George/
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Old February 20th, 2008, 04:40 AM   #3
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I have recently done some greenscreen with the EX1 and it works great! If you have the possibillities to capture the 10bit HD-SDI you will have some great looking footage! The best I have worked with that wasn't shoot on film.

Try to get your greenscreen exposure around 70%. That is a good starting point I think.
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Old February 20th, 2008, 05:27 AM   #4
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Quote:
Originally Posted by Geoff Jak View Post
It's been ages since I did a greenscreen and have forgotten about exposure of the screen.
Like they said. But for my tip:

Switch your Zebras to 70%, use the Zebras to evenly light your green screen.

Secret Sauce: DVmatte Pro, the new keyer from DV Garage. I swore by Zmatte for pulling keys from 4:2:0 sources, but now the new DVmatte Pro adds a difference matte to get even better edges. Talent settles in front of camera, lock it off, shoot, have the talent exit the frame (without moving the camera) and shoot 5 second plate of just the background. DVmatte Pro uses the difference to pull a fine key from it.
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Old February 20th, 2008, 12:55 PM   #5
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If you can get a shallow/short depth of field and have it fall off as close to (behind) the subject as possible. This will blur the background and even out glitches and uneveness.

Easiest way is to put some distance between you and the subject and use a larger aperture.

George/
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Old February 23rd, 2008, 12:18 AM   #6
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Thx very much everyone for your input. All valuable information and the job is now done with your help.
Cheers
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Old February 23rd, 2008, 11:24 AM   #7
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Zebra setting for flesh?

Quote:
Originally Posted by Matt Daviss View Post
Like they said. But for my tip:

Switch your Zebras to 70%, use the Zebras to evenly light your green screen.

Secret Sauce: DVmatte Pro, the new keyer from DV Garage. I swore by Zmatte for pulling keys from 4:2:0 sources, but now the new DVmatte Pro adds a difference matte to get even better edges. Talent settles in front of camera, lock it off, shoot, have the talent exit the frame (without moving the camera) and shoot 5 second plate of just the background. DVmatte Pro uses the difference to pull a fine key from it.
Thanks for the tip as well Matt, I am doing a green screen on Tuesday with female white talent. Aside from the 70 on the green, what would you suggest the setting be for flesh?
Best, Craig
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Old February 23rd, 2008, 11:36 AM   #8
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Aside from the 70 on the green, what would you suggest the setting be for flesh?
It's about the same for flesh tones - it's just that the trick with the 70% zebras to get a screen-full of stripes.

FWIW I usually switch to 100% zebras once I'm through doing the background lighting, as it's the blown highlights that spoil the day.

Note that dumping large quantities of light onto the background isn't the best thing. Evenness is what we want. In fact, too much light on the background bounces back onto the talent and you get hairy edges from the spill.

Good shooting!
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Old February 23rd, 2008, 12:13 PM   #9
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Thank you Richard

I appreciate your feedback and info...thnak you. I have purchased a good quality green screen and should be able to have it about 2 meters away from the talent. Thanks again.
Best, Craig
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Old February 25th, 2008, 11:18 AM   #10
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I'll be shooting my first EX1 green screen soon--any thoughts on preferred camera settings (both format and picture profile)? Mine is ending up on a website.
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Old February 25th, 2008, 11:24 AM   #11
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Just pick any progressive format; if your just shooting for the web 720p will usually be just fine. Or even the SD equivalent.

Choose profile/settings that suit our subject and follow suggestions above ;)

George/
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Old February 26th, 2008, 06:44 PM   #12
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shot it in 720p

I shot the chroma key piece today and it came out great!. My procedure was as follows.
The set was 10 feet wide x 10 feet high chroma key green material by eefx.com. Talent was white female standing /shot from waste up placed about 6 feet away from the wall. The wall was first lit with 4 tota lights with a 500 watt in each. 2 were on stands on either side and 2 were floor height angled upward toward the wall to fill in the lower half of the screen. I used 70 zebras to adjust lighting until even. The talent was lit with 2, 650 arris with softbox on either side and back lit with 2, 350 arris with yellow gels. The iris was then adjusted to 70 zebra on flesh.
The camera was set at 50p 720p and shutter at 125 to help eliminate motion blur.
The footage was brought into Final Cut and the key was so clean, even around the hair, I was amazed. The edited clips will be conveyed to England via data DVD compressed QT H.264. We brought the footage back into FCP having compressed this way, copied/pasted key attributes from original clip and they matched perfectly.
Hope this will be of some help...and thanks for the info from the prior posts...I very much appreciates the input.
Best, Craig Hollenabck
www.keysTV.com
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Old February 26th, 2008, 06:59 PM   #13
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So do we get to see a link to the green screen shot and the composite?

Inquiring eyes want to see.
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