Can someone help with strobing vision at DVinfo.net

Dennis Robinson · January 16th, 2005, 01:38 AM

Hi, I use an XL1s and edit in FCP4 on my 2.5 G5 with 30 inch display and have had this strobing effect to the vision when panning. It is slight and I must stress that it plays fine on a TV monitor. I get the strobing on my emac, ibook and pC with Prem Pro. I had a friend shoot some vision with his PD 150 and that stobes as well. Can anyone tell me what is causing this. Its like a slight stutter and only when panning. Even though it is ok printing to tape for television, the strobing appears in any DVD's I burn.

Ignacio Rodriguez · January 16th, 2005, 08:23 AM

You are probably seeing some kind of interlace artifact. If you are making progressive-scan DVDs at 25 fps in PAL you will need to keep camera movement to a minimum. You will very seldom see fast pans in feature films! If you need to decrease this kind of artifacting with material that has fast camera movement, you can try adding some slight motion blur in FCP before outputting to DVD. I prefer using the Stop Motion Blur plug-in instead of the clips Motion pane to add motion blur, as it gives more control. Note though this is one of the most processor-intensive things FCP can do so get ready to wait around for rendering a lot. A nice byproduct of motion blur is that it helps clear up video noise, I love the motion-blurred look, it's part of what I do to try to get a "film look" together with a non-linear transfer curve plug in.

Take a look at this thread for my latest comment on getting the "film" look from DV: http://www.dvinfo.net/conf/showthrea...threadid=35432

A. J. deLange · January 16th, 2005, 10:29 AM

If you are shooting "normal" (50i) mode then the video (vision) is being recorded as interlaced which means that the picture is separated into odd and even frames which are interlaced. Your computer monitor cannot do this interlacing and so shows both odd and even frames at the same time. If there is any movement between odd and even frames you will see a "blur" that looks as if the trailing edges of objects have fringes attached to them. If you can live with this during editing it is not a problem as it will not appear when the finished product is displayed on an interlaced TV set. If it is annoying to you the solution is to shoot in "frame" mode (25p). One slight caution here: the NTSC XL1s gives up a little resolution in frame mode and I suppose the PAL version will as well.

Ignacio Rodriguez · January 16th, 2005, 12:46 PM

> the NTSC XL1s gives up a little resolution
> in frame mode and I suppose the PAL version will as well

Yes. Deinterlacing in post --at least with the FCP plug-ins-- will also lose you some resolution. It's possible that going the way of frame mode is slightly better than deinterlacing in post.

Dennis Robinson · January 16th, 2005, 04:39 PM

Thanks guys for your help. It happens during slow pans and going by what you are saying, this happens to everybody. Is this correct? It certainly happens on all my computers and edit systems.

January 16th, 2005, 01:38 AM	#1
Dennis Robinson Major Player Join Date: Mar 2004 Location: Perth, Australia Posts: 250	Can someone help with strobing vision Hi, I use an XL1s and edit in FCP4 on my 2.5 G5 with 30 inch display and have had this strobing effect to the vision when panning. It is slight and I must stress that it plays fine on a TV monitor. I get the strobing on my emac, ibook and pC with Prem Pro. I had a friend shoot some vision with his PD 150 and that stobes as well. Can anyone tell me what is causing this. Its like a slight stutter and only when panning. Even though it is ok printing to tape for television, the strobing appears in any DVD's I burn. __________________ Dennis Robinson G5, , 30 inch display, FCP6 Studio 2, JVC-GYHD111

January 16th, 2005, 08:23 AM	#2
Ignacio Rodriguez Contributor Join Date: Sep 2003 Location: Santiago, Chile Posts: 932	You are probably seeing some kind of interlace artifact. If you are making progressive-scan DVDs at 25 fps in PAL you will need to keep camera movement to a minimum. You will very seldom see fast pans in feature films! If you need to decrease this kind of artifacting with material that has fast camera movement, you can try adding some slight motion blur in FCP before outputting to DVD. I prefer using the Stop Motion Blur plug-in instead of the clips Motion pane to add motion blur, as it gives more control. Note though this is one of the most processor-intensive things FCP can do so get ready to wait around for rendering a lot. A nice byproduct of motion blur is that it helps clear up video noise, I love the motion-blurred look, it's part of what I do to try to get a "film look" together with a non-linear transfer curve plug in. Take a look at this thread for my latest comment on getting the "film" look from DV: http://www.dvinfo.net/conf/showthrea...threadid=35432 __________________ Ignacio Rodríguez in the third world. @micronauta on Twitter. Main hardware: brain, eyes, hands.

January 16th, 2005, 12:46 PM	#4
Ignacio Rodriguez Contributor Join Date: Sep 2003 Location: Santiago, Chile Posts: 932	> the NTSC XL1s gives up a little resolution > in frame mode and I suppose the PAL version will as well Yes. Deinterlacing in post --at least with the FCP plug-ins-- will also lose you some resolution. It's possible that going the way of frame mode is slightly better than deinterlacing in post. __________________ Ignacio Rodríguez in the third world. @micronauta on Twitter. Main hardware: brain, eyes, hands.

January 16th, 2005, 04:39 PM	#5
Dennis Robinson Major Player Join Date: Mar 2004 Location: Perth, Australia Posts: 250	Thanks guys for your help. It happens during slow pans and going by what you are saying, this happens to everybody. Is this correct? It certainly happens on all my computers and edit systems. __________________ Dennis Robinson G5, , 30 inch display, FCP6 Studio 2, JVC-GYHD111

January 16th, 2005, 10:29 AM	#3
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	If you are shooting "normal" (50i) mode then the video (vision) is being recorded as interlaced which means that the picture is separated into odd and even frames which are interlaced. Your computer monitor cannot do this interlacing and so shows both odd and even frames at the same time. If there is any movement between odd and even frames you will see a "blur" that looks as if the trailing edges of objects have fringes attached to them. If you can live with this during editing it is not a problem as it will not appear when the finished product is displayed on an interlaced TV set. If it is annoying to you the solution is to shoot in "frame" mode (25p). One slight caution here: the NTSC XL1s gives up a little resolution in frame mode and I suppose the PAL version will as well.