Red ghosting at DVinfo.net

Tom Christensen · November 16th, 2002, 08:39 PM

Has anyone noticed a slight red ghosting when shooting a red or skin tone subject against a light or dark background. I seem to get this more in low light situations and have tried dialing it away with color gain, etc. but don't want to wash away all the red. I noticed this shooting a baseball jersey which was orange lettering on black background and when shooting my own head against a light background. The glow always seem to shift left off of the red part of the image which is suspect. Reminds me of when my old big screen TV would lose the color alignment.

Of course, now my eyes go right to the red part of my shots and my paranoia takes over.

Any ideas on how to get rid of this or can this possibly be a problem with the cam?

Tom

Jeff Donald · November 16th, 2002, 09:22 PM

Can you post a high rez example of the color shift? This may be similar to the color artifact (fringing) the Panasonic DVX100 is experiencing. I've seen good results using an 85B filter and white balancing through the filter. It's hard to say if your experiencing the same thing without seeing some shoots though.

Jeff

Bill Hardy · November 17th, 2002, 06:24 AM

Anyone can aim their GL2 at a colored illuminated sign at night and see this anomaly. The bleeding can appear as vertical lines. It is less obvious on a TV monitor than a computer screen I have noticed.

Tom Christensen · November 17th, 2002, 12:02 PM

Here's an example.

This is the uncompressed file with me against a light wall:

http://www.arcsand.com/images/redghost.tif

Here's my ear enlarged with the red halo:

http://www.arcsand.com/images/ear.tif

These are PC based tif files. Let me know if you have any trouble with viewing or downloading.

Tom

Jeff Donald · November 17th, 2002, 12:13 PM

What software and hardware are you using to capture your footage into the PC? It could be the Codec that the software is using. It could be related to the pixel shift technology that Canon and Panasonic use.

Jeff

Tom Christensen · November 17th, 2002, 01:26 PM

I use PC firewire to Premiere, but I can see the effect by just running the camera to the TV or through the view finder.

Tom Christensen · November 17th, 2002, 01:28 PM

. . .and I was shooting in Frame mode.

Peter Moore · November 17th, 2002, 03:09 PM

Others have mentioned this problem, and it does indeed exist. I don't think it's horrendously severe, though I wonder if software could be made to correct it. (shift the entire red component of the image over one pixel to the right).

Jeff Donald · November 17th, 2002, 03:22 PM

It would seem to be the pixel shift technology to blame if your seeing it on direct playback to a monitor. You might try the 85B filter. Some Panasonic DVX100 (Panasonic makes the chips in the GL2) users are reporting success using the 85B. It compensates for a lack of sensitivity in the blue wave lengths. Hopefully your near a camera store and they let you try before you buy.

If the filter fails to make any corrections I would contact Canon and ask their advice. They may be able to offer some additional insights.

Jeff

Tom Christensen · November 17th, 2002, 04:16 PM

Thanks for the filter suggestion. I will give it a try and remember to not shoot anyone's ear against a light bg. :)

Tom

Andre De Clercq · November 18th, 2002, 09:25 AM

Of course Y/C delay adjustment is standard in most TB correctors. The point is however if the problem is one of delay matching or color leakage (or both). To verify this just shoot a flat white or yellow suface with a piece of red tape vertically in the center (do the same with green and blue tape). If the leakage is the same left and right of the tape it's a color bandwidth problem. If you see it non symmetrical it's a delay problem. If you see differences in behaviour for different colors maybe there is something wrong with yr camera. Horizontal color resolution isn't all that good in the 4:1:1 NTSC DV system (only 25% of the luma resolution) and thus color leakage is not far away...

Tom Christensen · November 20th, 2002, 10:21 AM

Thanks for all the advice. I tried the red tape on a white and then black background and Yikes!!!, fringing was very obvious. It became worse the farther away the tape was, so close up it was slight but moving away from the tape, the thing glowed. It also seem to be consistent all around the tape with maybe a little more on the left. Didn't try other colors and haven't had a chance to get the filter.

Now having done a little more research on this, I find that it is a common problem in DV and looking at footage from other sources, I see it all the time with red. That said, I've for the most part ruled out that it's a problem with my camera.

I tried experimenting with some of the effects in Aftereffects and the only thing that really worked was cranking up the contrast. Some of the channel mixers actually made it worse. Color replace didn't really work etc.

I'd love to know if anyone has had any luck with this in post.

Tom

November 16th, 2002, 08:39 PM	#1
Tom Christensen Regular Crew Join Date: Aug 2002 Location: Cave Creek, AZ Posts: 87	Red ghosting Has anyone noticed a slight red ghosting when shooting a red or skin tone subject against a light or dark background. I seem to get this more in low light situations and have tried dialing it away with color gain, etc. but don't want to wash away all the red. I noticed this shooting a baseball jersey which was orange lettering on black background and when shooting my own head against a light background. The glow always seem to shift left off of the red part of the image which is suspect. Reminds me of when my old big screen TV would lose the color alignment. Of course, now my eyes go right to the red part of my shots and my paranoia takes over. Any ideas on how to get rid of this or can this possibly be a problem with the cam? Tom __________________ Tom Christensen

November 20th, 2002, 10:21 AM	#12
Tom Christensen Regular Crew Join Date: Aug 2002 Location: Cave Creek, AZ Posts: 87	Thanks for all the advice. I tried the red tape on a white and then black background and Yikes!!!, fringing was very obvious. It became worse the farther away the tape was, so close up it was slight but moving away from the tape, the thing glowed. It also seem to be consistent all around the tape with maybe a little more on the left. Didn't try other colors and haven't had a chance to get the filter. Now having done a little more research on this, I find that it is a common problem in DV and looking at footage from other sources, I see it all the time with red. That said, I've for the most part ruled out that it's a problem with my camera. I tried experimenting with some of the effects in Aftereffects and the only thing that really worked was cranking up the contrast. Some of the channel mixers actually made it worse. Color replace didn't really work etc. I'd love to know if anyone has had any luck with this in post. Tom __________________ Tom Christensen

November 16th, 2002, 09:22 PM	#2
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	Can you post a high rez example of the color shift? This may be similar to the color artifact (fringing) the Panasonic DVX100 is experiencing. I've seen good results using an 85B filter and white balancing through the filter. It's hard to say if your experiencing the same thing without seeing some shoots though. Jeff

November 17th, 2002, 06:24 AM	#3
Bill Hardy Major Player Join Date: Sep 2002 Posts: 205	Anyone can aim their GL2 at a colored illuminated sign at night and see this anomaly. The bleeding can appear as vertical lines. It is less obvious on a TV monitor than a computer screen I have noticed.

November 17th, 2002, 12:02 PM	#4
Tom Christensen Regular Crew Join Date: Aug 2002 Location: Cave Creek, AZ Posts: 87	Here's an example. This is the uncompressed file with me against a light wall: http://www.arcsand.com/images/redghost.tif Here's my ear enlarged with the red halo: http://www.arcsand.com/images/ear.tif These are PC based tif files. Let me know if you have any trouble with viewing or downloading. Tom

November 17th, 2002, 12:13 PM	#5
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	What software and hardware are you using to capture your footage into the PC? It could be the Codec that the software is using. It could be related to the pixel shift technology that Canon and Panasonic use. Jeff

November 17th, 2002, 01:26 PM	#6
Tom Christensen Regular Crew Join Date: Aug 2002 Location: Cave Creek, AZ Posts: 87	I use PC firewire to Premiere, but I can see the effect by just running the camera to the TV or through the view finder.

November 17th, 2002, 01:28 PM	#7
Tom Christensen Regular Crew Join Date: Aug 2002 Location: Cave Creek, AZ Posts: 87	. . .and I was shooting in Frame mode.

November 17th, 2002, 03:09 PM	#8
Peter Moore Trustee Join Date: Oct 2002 Location: Arlington VA Posts: 1,034	Others have mentioned this problem, and it does indeed exist. I don't think it's horrendously severe, though I wonder if software could be made to correct it. (shift the entire red component of the image over one pixel to the right).

November 17th, 2002, 03:22 PM	#9
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	It would seem to be the pixel shift technology to blame if your seeing it on direct playback to a monitor. You might try the 85B filter. Some Panasonic DVX100 (Panasonic makes the chips in the GL2) users are reporting success using the 85B. It compensates for a lack of sensitivity in the blue wave lengths. Hopefully your near a camera store and they let you try before you buy. If the filter fails to make any corrections I would contact Canon and ask their advice. They may be able to offer some additional insights. Jeff

November 17th, 2002, 04:16 PM	#10
Tom Christensen Regular Crew Join Date: Aug 2002 Location: Cave Creek, AZ Posts: 87	Thanks for the filter suggestion. I will give it a try and remember to not shoot anyone's ear against a light bg. :) Tom

November 18th, 2002, 09:25 AM	#11
Andre De Clercq Major Player Join Date: Sep 2002 Location: Belgium Posts: 804	Of course Y/C delay adjustment is standard in most TB correctors. The point is however if the problem is one of delay matching or color leakage (or both). To verify this just shoot a flat white or yellow suface with a piece of red tape vertically in the center (do the same with green and blue tape). If the leakage is the same left and right of the tape it's a color bandwidth problem. If you see it non symmetrical it's a delay problem. If you see differences in behaviour for different colors maybe there is something wrong with yr camera. Horizontal color resolution isn't all that good in the 4:1:1 NTSC DV system (only 25% of the luma resolution) and thus color leakage is not far away...