Lighting changing without my permission! at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > Photon Management

Photon Management
Shine an ever-loving light on you.


Reply
 
Thread Tools Search this Thread
Old November 21st, 2008, 06:45 PM   #1
Ryan Jones
 
Posts: n/a
Lighting changing without my permission!

Im shooting HD green screen interview-type stuff using a couple 250w photoflex studio series lights to light the subject and the greenscreen. I know its a pretty crappy setup; ive got some 1000w w/softboxes on the way so I can light the subject correctly (the footage is very passable atm tho). Im shooting with a canon xh a1 using all manual controls.

So my problem is that when i scrub through my footage in FCP i see the greenscreen changing brightness about every 6-10 seconds then coming back to normal. Its not very noticable in real time, but it still bothers me and makes some keying troublesome. The lights don't appear to be glowing back and forth like this and the iris and shutter speed are both set manually (Ive had it happen in different settings).

Any ideas?
  Reply With Quote
Old November 22nd, 2008, 02:41 AM   #2
Inner Circle
 
Join Date: Oct 2001
Location: Honolulu, HI
Posts: 2,053
Sounds like you have unstable power for whatever reason. Could be something in the building is drawing lots of amps and is drawing your lights down with it.
__________________
Dean Sensui
Exec Producer, Hawaii Goes Fishing
Dean Sensui is offline   Reply With Quote
Old November 22nd, 2008, 06:25 AM   #3
Inner Circle
 
Join Date: Sep 2002
Location: Vancouver, British Columbia (formerly Winnipeg, Manitoba) Canada
Posts: 4,087
Sounds like fluorescents with a shutter speed other than 1/60 (1/50 in PAL countries). Can you confirm that you ARE using tungstens? Were the room lights (overhead fluorescent) on?
__________________
Shaun C. Roemich Road Dog Media - Vancouver, BC - Videographer - Webcaster
www.roaddogmedia.ca Blog: http://roaddogmedia.wordpress.com/
Shaun Roemich is offline   Reply With Quote
Old November 22nd, 2008, 10:14 AM   #4
Major Player
 
Join Date: Feb 2006
Location: Louisville, KY
Posts: 591
any natural light coming in from windows or skylights? Natural light shifts. AC or Heat coming on and off can drop the line voltage as well.

It's possible ( I can't vouch for this ) that putting a surge protector between the wall socket and your lamps might solve the problem.
Christopher Witz is offline   Reply With Quote
Old November 22nd, 2008, 12:31 PM   #5
Regular Crew
 
Join Date: Dec 2006
Location: Tampa-Orlando, FL
Posts: 124
Are you using dimmers?
__________________
NinoMedia Productions - EFPLighting.com Advanced Lighting and Gripping Workshops
Nino Giannotti is offline   Reply With Quote
Old November 22nd, 2008, 01:57 PM   #6
Contributor
 
Join Date: Jan 2003
Location: Kansas City, MO
Posts: 4,449
Double check to be sure you don't have auto shutter or auto white balance on. If everythng is truly manual, then it's got to be some sort of power fluctuation or fluorescent flickering. I'd use a voltmeter to check the power first.
Bill Pryor is offline   Reply With Quote
Old November 22nd, 2008, 03:03 PM   #7
Trustee
 
Join Date: Jan 2004
Location: Scottsdale, AZ 85260
Posts: 1,538
I believe it's clear that you are using TEENAGE lights.

Teenagers historically do stuff without permission. It's why they're teenagers.

Baby lights are often quite limited. Teenage lights unruly. Only fully adult lights can be expected to give you predictable results in most situations.

When the lights you use grow up a bit, it'll be easier for you to reason with them.

Good luck.

;)
Bill Davis is offline   Reply With Quote
Old November 24th, 2008, 02:42 PM   #8
Ryan Jones
 
Posts: n/a
Quote:
Originally Posted by Shaun Roemich View Post
Sounds like fluorescents with a shutter speed other than 1/60 (1/50 in PAL countries). Can you confirm that you ARE using tungstens? Were the room lights (overhead fluorescent) on?
overhead flourescents were on. Im in a cramped office building where turning off the lights turns off our whole office's lights haha. Will shooting with a 1/60 shutter speed allow me to keep the overheads on? I shoot often and i can't have the whole office's lights off whenever i please; I can't move locations either.

Thanks everyone for the replies. This forum is full of video sages!
  Reply With Quote
Old November 24th, 2008, 02:50 PM   #9
Contributor
 
Join Date: Jan 2003
Location: Kansas City, MO
Posts: 4,449
I shoot all the time under fluorescents doing 24F at a 1/48 shutter speed, and if I do interlaced, I shoot at 1/60. Any other speed might cause a flickering. However, you describe the change as happening every 6 + seconds. That doesn't sound like a fluorescent flicker to me. I'd vote for a power fluctuation.
Bill Pryor is offline   Reply With Quote
Old November 24th, 2008, 05:41 PM   #10
Major Player
 
Join Date: Mar 2006
Location: Chicago
Posts: 706
A light meter would help to eliminate the possibility of a 60hz or camera problem. I would want to know if the actual light level is varying before hunting down electrical problems.
Don Miller is offline   Reply With Quote
Old November 24th, 2008, 09:34 PM   #11
Major Player
 
Join Date: Jan 2008
Location: Orlando, FL
Posts: 558
Quote:
Originally Posted by Bill Davis View Post
I believe it's clear that you are using TEENAGE lights.

Teenagers historically do stuff without permission. It's why they're teenagers.

Baby lights are often quite limited. Teenage lights unruly. Only fully adult lights can be expected to give you predictable results in most situations.

When the lights you use grow up a bit, it'll be easier for you to reason with them.

Good luck.

;)
love it!


Also, be sure your background isn't floating around, sometimes shadows can cause differences.

JS
John Stakes is offline   Reply With Quote
Old November 26th, 2008, 06:18 PM   #12
Inner Circle
 
Join Date: Sep 2002
Location: Vancouver, British Columbia (formerly Winnipeg, Manitoba) Canada
Posts: 4,087
Quote:
Originally Posted by Bill Pryor View Post
However, you describe the change as happening every 6 + seconds. That doesn't sound like a fluorescent flicker to me. I'd vote for a power fluctuation.
If it CYCLES over a period of 6+ seconds as opposed to changing intensity, it certainly does sound like fluoros.

The non-sustained RGB nature of consumer fluoros (as opposed to sRGB pro lights) causes the light spectrum to "roll" under non source frequency exposure (ie 1/100th shutter using 60Hz power). Sorry, I should have been more specific.
__________________
Shaun C. Roemich Road Dog Media - Vancouver, BC - Videographer - Webcaster
www.roaddogmedia.ca Blog: http://roaddogmedia.wordpress.com/
Shaun Roemich is offline   Reply With Quote
Old November 26th, 2008, 06:21 PM   #13
Inner Circle
 
Join Date: Sep 2002
Location: Vancouver, British Columbia (formerly Winnipeg, Manitoba) Canada
Posts: 4,087
As well, are you using "emergency" power outlets that are designed to maintain power in a blackout, for example: in a hospital? I plugged my lights into orange/red outlets this morning (emergency power) and noticed that intensity shifted occasionally. First time I ever noticed it.
__________________
Shaun C. Roemich Road Dog Media - Vancouver, BC - Videographer - Webcaster
www.roaddogmedia.ca Blog: http://roaddogmedia.wordpress.com/
Shaun Roemich is offline   Reply With Quote
Old November 27th, 2008, 02:04 AM   #14
Trustee
 
Join Date: Apr 2006
Location: United States
Posts: 1,158
indeed, its the flouro's causing a problem. while 24.000 is 60hz safe, 23.976 which video cameras use ( exceptions like F900/950, ect where its specific ) is not at 1/48th. if you shutter at 1/60th, all will be good again.

you could losen the bulbs in the shooting area to get them off, especially if its one room. another options is some heavy black plastic to kill them. more likely though, they are a help so just run with 1.60th and life will be good.
Steve Oakley is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > Photon Management

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 08:52 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network