Color shift while shooting LCD projector w/HM100 at DVinfo.net

James Downie · September 23rd, 2009, 06:24 PM

90% of my business is shooting legal depositions. I normally use my trusty PD170, but I had a client that insisted that I shoot this one in HD. No reason was given to me. I bought my HM100 a couple months ago and haven't been able to use it much, so this sounded like a good opportunity to take it in the field. When I got there the attorney told me that the witness would be using a Keynote presentation connected to a LCD projector and he wanted me to pan between the witness and the screen. I knew this would look like garbage, but he's the boss. Anyway, when I was focused on the witness, everything was fine. When I panned to the screen, the video seemed to be "throbbing" between a bluish and greenish hue. When I panned back to the witness, all was fine once again. Then I swing back over to the screen and the throbbing starts again. I started shooting in full auto. The first time it started to go crazy, I switched over to manual, thinking the white screen was doing something to the iris control. Same result. Anybody have any ideas what's going on? This is my first foray into HD. I've shot similar shots with my PD170 and I've never seen this before.

Thanks.

James Downie
Blufish Media
Charlotte, NC

John Mitchell · September 23rd, 2009, 07:49 PM

James I would hazard a guess that the frame rate of the projector was different from your camera. Next time try using the shutter to get rid of the strobing effect. The green and blue is your sensor picking up the different parts of the colour wheel of the projector.

Data projectors, computer screens etc are notoriously difficult to film because they normally operate at high frequency and often contain detail which causes moire on todays cameras..

Of course if you've ruled out these obvious things then it's soemthign else...\

James Downie · September 24th, 2009, 07:35 AM

John, thanks. I knew about shooting computer monitors, but I didn't think this was the same thing because I wasn't getting the flicker, just the colors. I know I've done the same thing with my other camera without the issues. Maybe this camera is just more sensitive. I'll keep that in mind next time.

Thanks for your help!

JD

David Walton · September 25th, 2009, 09:21 PM

James, are you sure that it was an LCD projector, and not a DLP? Many of the lower cost DLP projectors use a spinning color wheel with a single projection chip. They make "color" on the screen by alternating R-G-B images so quickly that your eyes think they're seeing a color image. They can cause very unpredictable effects when shooting the screen with a video camera. If this is the case, my only suggestion is to try different shutter speeds (perhaps a lower speed shutter when shooting the screen.)

dave walton
JVC

September 23rd, 2009, 06:24 PM	#1
James Downie Regular Crew Join Date: Nov 2005 Location: Charlotte, NC USA Posts: 39	Color shift while shooting LCD projector w/HM100 90% of my business is shooting legal depositions. I normally use my trusty PD170, but I had a client that insisted that I shoot this one in HD. No reason was given to me. I bought my HM100 a couple months ago and haven't been able to use it much, so this sounded like a good opportunity to take it in the field. When I got there the attorney told me that the witness would be using a Keynote presentation connected to a LCD projector and he wanted me to pan between the witness and the screen. I knew this would look like garbage, but he's the boss. Anyway, when I was focused on the witness, everything was fine. When I panned to the screen, the video seemed to be "throbbing" between a bluish and greenish hue. When I panned back to the witness, all was fine once again. Then I swing back over to the screen and the throbbing starts again. I started shooting in full auto. The first time it started to go crazy, I switched over to manual, thinking the white screen was doing something to the iris control. Same result. Anybody have any ideas what's going on? This is my first foray into HD. I've shot similar shots with my PD170 and I've never seen this before. Thanks. James Downie Blufish Media Charlotte, NC

September 23rd, 2009, 07:49 PM	#2
John Mitchell Contributor Join Date: Jul 2005 Location: Sydney Australia Posts: 873	James I would hazard a guess that the frame rate of the projector was different from your camera. Next time try using the shutter to get rid of the strobing effect. The green and blue is your sensor picking up the different parts of the colour wheel of the projector. Data projectors, computer screens etc are notoriously difficult to film because they normally operate at high frequency and often contain detail which causes moire on todays cameras.. Of course if you've ruled out these obvious things then it's soemthign else...\

September 24th, 2009, 07:35 AM	#3
James Downie Regular Crew Join Date: Nov 2005 Location: Charlotte, NC USA Posts: 39	John, thanks. I knew about shooting computer monitors, but I didn't think this was the same thing because I wasn't getting the flicker, just the colors. I know I've done the same thing with my other camera without the issues. Maybe this camera is just more sensitive. I'll keep that in mind next time. Thanks for your help! JD

September 25th, 2009, 09:21 PM	#4
David Walton JVC Join Date: Feb 2006 Posts: 13	James, are you sure that it was an LCD projector, and not a DLP? Many of the lower cost DLP projectors use a spinning color wheel with a single projection chip. They make "color" on the screen by alternating R-G-B images so quickly that your eyes think they're seeing a color image. They can cause very unpredictable effects when shooting the screen with a video camera. If this is the case, my only suggestion is to try different shutter speeds (perhaps a lower speed shutter when shooting the screen.) dave walton JVC