Flash induced artifacts at DVinfo.net

Peter Rush · September 18th, 2012, 05:53 AM

Hi All

As we all have to cope with lots of flashes going off during our shoots - has anyone got an explanation as to why I quite often get (usually when filming in low lights) MPEG artifacts showing the frame before and the frame after the flash - it's not a biggie but I wonder if there is a way around it

Pete

Mark Williams · September 18th, 2012, 06:22 AM

Got a notice on this new product that might help Announcing Flash Remover Pro from NewBlueFX

Jeff Pulera · September 18th, 2012, 08:09 AM

Hi Pete,

Are you shooting HDV? I see what you describe when shooting dark wedding reception dances in HDV. This is a Long-GOP format, which means only two FULL frames are recorded each second. In the 29.97fps US format, that means a full frame every 15 frames. What about the rest of the frames? They record partial information, meaning the "changes" from the full frames. So the full frames before and after the partial frames are referenced to get more info to complete the picture. I believe when shooting a dark scene with little picture info, the sudden intense lighting, and accompanying detail, are simply more than the codec is capable of handling so it breaks up into lovely blocks unfortunately.

Some folks like to use an outboard recorder like the Atomos Ninja to pull the HDMI feed out of the camera before it gets compressed, and then record that to more robust, high data rate, intra-frame codec like ProRes 422 that would avoid said compression issues.

Thanks

Jeff Pulera
Safe Harbor

September 18th, 2012, 05:53 AM	#1
Peter Rush Inner Circle Join Date: Nov 2008 Location: UK/Yorkshire Posts: 2,069	Flash induced artifacts Hi All As we all have to cope with lots of flashes going off during our shoots - has anyone got an explanation as to why I quite often get (usually when filming in low lights) MPEG artifacts showing the frame before and the frame after the flash - it's not a biggie but I wonder if there is a way around it Pete

September 18th, 2012, 06:22 AM	#2
Mark Williams Trustee Join Date: Dec 2002 Location: Deep South, U.S. Posts: 1,526	Re: Flash induced artifacts Got a notice on this new product that might help Announcing Flash Remover Pro from NewBlueFX __________________ Mark videos: http://vimeo.com/channels/3523 Stock: http://www.pond5.com/artist/mark29

September 18th, 2012, 08:09 AM	#3
Jeff Pulera Major Player Join Date: Jun 2008 Location: Milwaukee WI Posts: 691	Re: Flash induced artifacts Hi Pete, Are you shooting HDV? I see what you describe when shooting dark wedding reception dances in HDV. This is a Long-GOP format, which means only two FULL frames are recorded each second. In the 29.97fps US format, that means a full frame every 15 frames. What about the rest of the frames? They record partial information, meaning the "changes" from the full frames. So the full frames before and after the partial frames are referenced to get more info to complete the picture. I believe when shooting a dark scene with little picture info, the sudden intense lighting, and accompanying detail, are simply more than the codec is capable of handling so it breaks up into lovely blocks unfortunately. Some folks like to use an outboard recorder like the Atomos Ninja to pull the HDMI feed out of the camera before it gets compressed, and then record that to more robust, high data rate, intra-frame codec like ProRes 422 that would avoid said compression issues. Thanks Jeff Pulera Safe Harbor