Strobe effect with stage lights at DVinfo.net

Greg Hawkes · July 4th, 2011, 12:07 PM

My friend filmed a dance show with his two Ex3s set to 1280 x 720 progressive .
Everything looked ok in the LCD whilst filming.

Later when converting the cards to SD using the Sony EX30 for editing with Adobe Premiere 6.5 the strobing was very apparent.

Can anybody suggest a possible fix?

Dave Sperling · July 4th, 2011, 01:17 PM

Can you be more specific about the strobing?
Is it a pulsing/flickering particularly noticeable in the highlights (usually caused by the camera running at a different frame rate than the ballast of an emission light source) -- if so, does it happen with all light sources or just a certain highlight?
Or is it a motion strobing exascerbated by converting from progressive to interlaced?
When played back in the camera (and/or from the camera onto a monitor) is the strobing visible?
What frame rate was used when shooting the footage? / What frame rate is it being converted to?

Greg Hawkes · July 4th, 2011, 02:14 PM

Hi Dave

Thanks for your reply.

Frame rate is 50 fps. Being converted to SD 25 fps.

Sorry to be vague but details not fully supplied by my friend.

Could well be changing from progressive to interlace in the donwconversion.

Dave Blackhurst · July 4th, 2011, 05:57 PM

You may be seeing the results of LED lights - multiple reports across several forums here...

Apparently these LED lights "pulse" for want of a better term - not exactly strobing, more of a "water" look is how I'd describe it. Even saw a bit of it in the background on footage posted shot with a RED! Showing up in a lot of footage, no "solution" other than overpowering the "bad" lighting, it seems to be something with the dimmers and cheap LED arrays judging from the reports.

If you search the forums, I think you'll find others running into this...

Dave Sperling · July 4th, 2011, 08:25 PM

Hi Dave,
It's not necessarily just the 'cheap' LEDs that can cause problems. We recently shot a Broadway show that utilized a lot of LED screens that they were paying big bucks for, and ended up going with a fairly unusual shutter angle to get rid of an occasional black pulse that we were seeing in the screen image. Took some time (working with the stage crew in advance of the performance) to figure out the issue and dial it in.

Bruce Rawlings · July 9th, 2011, 01:42 PM

Recently had this with an HDCAM 730 camera. Solved by going into computer ECS scan mode and dialing out the problem. I think EX cameras have similar shutter.

July 4th, 2011, 12:07 PM	#1
Greg Hawkes Regular Crew Join Date: Oct 2007 Location: Basingstoke Posts: 83	Strobe effect with stage lights My friend filmed a dance show with his two Ex3s set to 1280 x 720 progressive . Everything looked ok in the LCD whilst filming. Later when converting the cards to SD using the Sony EX30 for editing with Adobe Premiere 6.5 the strobing was very apparent. Can anybody suggest a possible fix?

July 4th, 2011, 01:17 PM	#2
Dave Sperling Major Player Join Date: Jan 2010 Location: Tinton Falls, NJ Posts: 780	Re: Strobe effect with stage lights Can you be more specific about the strobing? Is it a pulsing/flickering particularly noticeable in the highlights (usually caused by the camera running at a different frame rate than the ballast of an emission light source) -- if so, does it happen with all light sources or just a certain highlight? Or is it a motion strobing exascerbated by converting from progressive to interlaced? When played back in the camera (and/or from the camera onto a monitor) is the strobing visible? What frame rate was used when shooting the footage? / What frame rate is it being converted to?

July 4th, 2011, 02:14 PM	#3
Greg Hawkes Regular Crew Join Date: Oct 2007 Location: Basingstoke Posts: 83	Re: Strobe effect with stage lights Hi Dave Thanks for your reply. Frame rate is 50 fps. Being converted to SD 25 fps. Sorry to be vague but details not fully supplied by my friend. Could well be changing from progressive to interlace in the donwconversion.

July 4th, 2011, 05:57 PM	#4
Dave Blackhurst Inner Circle Join Date: Feb 2007 Location: Apple Valley CA Posts: 4,874	Re: Strobe effect with stage lights You may be seeing the results of LED lights - multiple reports across several forums here... Apparently these LED lights "pulse" for want of a better term - not exactly strobing, more of a "water" look is how I'd describe it. Even saw a bit of it in the background on footage posted shot with a RED! Showing up in a lot of footage, no "solution" other than overpowering the "bad" lighting, it seems to be something with the dimmers and cheap LED arrays judging from the reports. If you search the forums, I think you'll find others running into this...

July 4th, 2011, 08:25 PM	#5
Dave Sperling Major Player Join Date: Jan 2010 Location: Tinton Falls, NJ Posts: 780	Re: Strobe effect with stage lights Hi Dave, It's not necessarily just the 'cheap' LEDs that can cause problems. We recently shot a Broadway show that utilized a lot of LED screens that they were paying big bucks for, and ended up going with a fairly unusual shutter angle to get rid of an occasional black pulse that we were seeing in the screen image. Took some time (working with the stage crew in advance of the performance) to figure out the issue and dial it in.

July 9th, 2011, 01:42 PM	#6
Bruce Rawlings Major Player Join Date: Feb 2008 Location: Cardiff, Wales, UK Posts: 410	Re: Strobe effect with stage lights Recently had this with an HDCAM 730 camera. Solved by going into computer ECS scan mode and dialing out the problem. I think EX cameras have similar shutter.

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