Filter for reducing vertical smear? at DVinfo.net

Brandt Wilson · June 6th, 2003, 03:48 PM

Could a pola or grating filter be used to minimize the vertical smear on bright light sources?

Boyd Ostroff · June 6th, 2003, 08:15 PM

From what I've seen on the PDX-10, there is a certain contrast threshold at which the smear becomes objectionable with a bright point light source. Not sure how one could change that with a filter. For example, I have a video of a sunset. It's fine while the sun is behind some thin clouds. But as they slowly move away a vertical line becomes visible. It isn't objectionable at first, in fact I like the effect. But as the cloud fully passes the sun the smear becomes an opaque white line, which looks bad.

Jan Roovers · June 7th, 2003, 02:28 AM

I found this article:
Smear in CCD-sensors

Jan

John Jay · June 8th, 2003, 01:16 PM

if you mean optical filter then the answer is no

however there is an nle filter which is a godsend

get video finesse from synthetic aperture site, amongst the suite is a nice little filter called 'sa dropout'. it was designed to remove the white horizontal streaks from analog footage but it can be made to work in the vertical direction

if your nle is premier plugin compatible heres what you do

1 create a project 720x720

2 get your affected footage into this project and maintain aspect ratio

3 rotate the footage 90 degrees

4 apply sa dropout filter (tweak the sliders until the lines disappear)

5 rotate the footage -90 degrees
(3,4 &5 are done in one step by stacking the filters)

6 crop and render out to 720x480 or 720x576 dv codified

hey presto - no white lines!!

Brandt Wilson · June 8th, 2003, 08:32 PM

john,

this sounds pretty incredible. How effective is it at restoring a clean image where the vertical smear was?

John Jay · June 9th, 2003, 06:54 PM

Brandt,

what can i say apart from it works on removing those thin white vertical lines

try it

Steve Pierce · June 10th, 2003, 04:02 PM

Does anyone have any links to pdx10 footage displaying the vertical smear problem? I've noticed it in several still images but not video.

For example, on Jan Roovers' website (www.jtv.be), there is one video (Snow on the Sengel) where the only light is from streetlamps. I didn't notice any vertical smear (just wondering, having a PAL rather than NTSC camera wouldn't make any difference here, would it?).

What does vertical smear look like on video? Does the white line disappear and reappear as you pan sideways or is it there constantly?

Boyd Ostroff · June 10th, 2003, 08:49 PM

Steve,

I've uploaded a short example of a sunset which shows the problem. The sun drops below the clouds and gets brighter. At first it doesn't look bad, sort of a star filter effect. But it reaches a certain threshold where it turns into an opaque vertical bar. Note that this is a pretty extreme test however, shooting directly into the sun.

The video is compressed with sorenson 3 at 428x240 (scaled with Quicktime pro into the 16:9 aspect ratio). It has been reduced to 8 fps, and also sped up by 800% in FCP. It's a 1.7MB file which runs for about 18 seconds (also note the time lapse jet that leaves a vapor trail on the right side of the image right at the end :-)

http://www.greenmist.com/pdx10/smear

June 6th, 2003, 03:48 PM	#1
Brandt Wilson Major Player Join Date: Jan 2003 Location: Portland, OR Posts: 220	Filter for reducing vertical smear? Could a pola or grating filter be used to minimize the vertical smear on bright light sources?

June 7th, 2003, 02:28 AM	#3
Jan Roovers Regular Crew Join Date: Mar 2003 Location: Amsterdam NL -Turnhout BE Posts: 158	I found this article: Smear in CCD-sensors Jan __________________ ___________ Jan Roovers www.jtv.be

June 8th, 2003, 01:16 PM	#4
John Jay Major Player Join Date: Sep 2002 Location: US & THEM Posts: 827	if you mean optical filter then the answer is no however there is an nle filter which is a godsend get video finesse from synthetic aperture site, amongst the suite is a nice little filter called 'sa dropout'. it was designed to remove the white horizontal streaks from analog footage but it can be made to work in the vertical direction if your nle is premier plugin compatible heres what you do 1 create a project 720x720 2 get your affected footage into this project and maintain aspect ratio 3 rotate the footage 90 degrees 4 apply sa dropout filter (tweak the sliders until the lines disappear) 5 rotate the footage -90 degrees (3,4 &5 are done in one step by stacking the filters) 6 crop and render out to 720x480 or 720x576 dv codified hey presto - no white lines!! __________________ John Jay Beware *PLUGGER-BYTES*

June 8th, 2003, 08:32 PM	#5
Brandt Wilson Major Player Join Date: Jan 2003 Location: Portland, OR Posts: 220	video finesse john, this sounds pretty incredible. How effective is it at restoring a clean image where the vertical smear was?

June 9th, 2003, 06:54 PM	#6
John Jay Major Player Join Date: Sep 2002 Location: US & THEM Posts: 827	Brandt, what can i say apart from it works on removing those thin white vertical lines try it __________________ John Jay Beware *PLUGGER-BYTES*

June 6th, 2003, 08:15 PM	#2
Boyd Ostroff Wrangler Join Date: Dec 2002 Location: Mays Landing, NJ Posts: 11,802	From what I've seen on the PDX-10, there is a certain contrast threshold at which the smear becomes objectionable with a bright point light source. Not sure how one could change that with a filter. For example, I have a video of a sunset. It's fine while the sun is behind some thin clouds. But as they slowly move away a vertical line becomes visible. It isn't objectionable at first, in fact I like the effect. But as the cloud fully passes the sun the smear becomes an opaque white line, which looks bad.

June 10th, 2003, 04:02 PM	#7
Steve Pierce New Boot Join Date: May 2003 Location: Cardiff, UK Posts: 18	Does anyone have any links to pdx10 footage displaying the vertical smear problem? I've noticed it in several still images but not video. For example, on Jan Roovers' website (www.jtv.be), there is one video (Snow on the Sengel) where the only light is from streetlamps. I didn't notice any vertical smear (just wondering, having a PAL rather than NTSC camera wouldn't make any difference here, would it?). What does vertical smear look like on video? Does the white line disappear and reappear as you pan sideways or is it there constantly?

June 10th, 2003, 08:49 PM	#8
Boyd Ostroff Wrangler Join Date: Dec 2002 Location: Mays Landing, NJ Posts: 11,802	Steve, I've uploaded a short example of a sunset which shows the problem. The sun drops below the clouds and gets brighter. At first it doesn't look bad, sort of a star filter effect. But it reaches a certain threshold where it turns into an opaque vertical bar. Note that this is a pretty extreme test however, shooting directly into the sun. The video is compressed with sorenson 3 at 428x240 (scaled with Quicktime pro into the 16:9 aspect ratio). It has been reduced to 8 fps, and also sped up by 800% in FCP. It's a 1.7MB file which runs for about 18 seconds (also note the time lapse jet that leaves a vapor trail on the right side of the image right at the end :-) http://www.greenmist.com/pdx10/smear