Image Pulses 2X sec XH A1?

Raymond Toussaint · December 21st, 2006, 05:10 PM

Quote:

Originally Posted by John Huling

Well the files would not open but yes once you see it you notice it everytime for sure. I shot some more waterfalls this morning all manual. I used your ice setting. Still get that pulsing 2x second in the rocks shadows especially large smooth areas.

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John Huling · December 22nd, 2006, 05:34 AM

Can anyone else confirm that this pulsing or stobing with the Canon A1 is a GOP phenomenon? I am surprised to find no one finds it objectionable. A friend of mine shot with his 1/2 inch CCD DVCAM and I did not see this pulsing in the same footage shot at nearly the same settings on his camera on our HD monitor. I believe it was the 330 or 350 Sony

Alex Leith · December 22nd, 2006, 08:43 AM

Quote:

Originally Posted by John Huling

I believe it was the 330 or 350 Sony

If the F330/350 was operating in DVCAM mode there is no GOP (all frames are independent). If it was set to 35Mbit XDCAMHD then that pumps a reasonable amount of extra bandwidth that will help to minimise any pulsing.

Almost all MPEG-2 shows a degree of pulsing. Often you can't see it because it looks like the part of the "grain" of the image, or it's mostly in the shadows which are crushed or softened by tube TVs.

If you look hard enough you can find pulsing on most HDV cameras - and even if you can't by encoding for DVD will add it (although try using an open instead of closed GOP to minimise the effect). It's simply a limitation of the technology and not terribly distracting if you ignore it.

Alex Leith · December 22nd, 2006, 09:15 AM

I have to add, that normally I would hope that the GOP jumps weren't as noticable as it was in the Poppe clips - however...

HDV is a lossy codec with a limited amount of bandwidth to offer. The more moving detail there is in a shot the more that the MPEG compressor has to make "decisions" about what information they keep, and what they throw away. Particularly agressive motion on the Sony Z1/FX1 and Sony A1 shows up as large pixel blocks.

The Canon A1 seems to be able to handle fast motion better - but perhaps what we're seeing here is the flip side of that?

John Huling · December 22nd, 2006, 10:57 AM

Is there a setting you or someone could suggest to help minimize this pulsing strobing thing? A starting point anyway that you could suggest. I really do appreciate your help.
Also, is it possible to minimize this in post as well, now that I have several hours of otherwise very usable footage for my project?

December 22nd, 2006, 09:15 AM	#34
Alex Leith Major Player Join Date: Mar 2005 Location: Northampton, England Posts: 500	I have to add, that normally I would hope that the GOP jumps weren't as noticable as it was in the Poppe clips - however... HDV is a lossy codec with a limited amount of bandwidth to offer. The more moving detail there is in a shot the more that the MPEG compressor has to make "decisions" about what information they keep, and what they throw away. Particularly agressive motion on the Sony Z1/FX1 and Sony A1 shows up as large pixel blocks. The Canon A1 seems to be able to handle fast motion better - but perhaps what we're seeing here is the flip side of that? __________________ Alex

December 22nd, 2006, 05:34 AM	#32
John Huling Regular Crew Join Date: Nov 2006 Location: USA Posts: 172	Can anyone else confirm that this pulsing or stobing with the Canon A1 is a GOP phenomenon? I am surprised to find no one finds it objectionable. A friend of mine shot with his 1/2 inch CCD DVCAM and I did not see this pulsing in the same footage shot at nearly the same settings on his camera on our HD monitor. I believe it was the 330 or 350 Sony

December 22nd, 2006, 10:57 AM	#35
John Huling Regular Crew Join Date: Nov 2006 Location: USA Posts: 172	Is there a setting you or someone could suggest to help minimize this pulsing strobing thing? A starting point anyway that you could suggest. I really do appreciate your help. Also, is it possible to minimize this in post as well, now that I have several hours of otherwise very usable footage for my project?