Purple and green borders are killing me!!!

David Mills · February 19th, 2006, 06:49 PM

Barlow I just looked at your slo mo trampoline again. Have a look at the trees on the right. That green fringe is what I am getting. Whoah that's bad. On the other hand the slow mo is great.

Barlow Elton · February 19th, 2006, 07:07 PM

Hi David,

Oh yeah, it's there. I think I might have heightened it by adding a +2 color gain. I put up the CarlosDiego clip and it's ever so slight, but I think it's there too.

www.homepage.mac.com/mrbarlowelton

I think you're fine overall, but you might want to shoot flat for maximum latitude in post. Man, the CA would be the least of your concerns if the content's there. My low light footage has been phenomenal. You saw the "misc.Sundance2 clip", no CA. I have lit shots at slight tele that don't have the issue at all, and I bet a lot of your CU's will be max tele, if your going to use the 20x lens.

I think my advice would be to not push the color at full wide-angle. That's where I've seen the issue under specific circumstances.

It could be that the H1 is so damn sharp that it can't help but to have a little CA. I do know that it pixel shifts to achieve a full raster 1920x1080 SDI output...probably with the green pixels, so that might be contributing to the problem in some way.

David, I wouldn't worry so much. You'll get beautiful results, just watch for obvious contrasts (dark foregroud object, white background) and check for the anomaly. I doubt you're going to have any showstopping problems.

A. J. deLange · February 20th, 2006, 12:23 PM

It just occured to me that everyone concerned over this issue ought to turn on the color bars, record them to tape and capture a frame. I've posted a frame at http://www.pbase.com/agamid/image/53638038 for those who want to see immediately what to expect. The point is that there are pixel (or more) wide transition zones between color bars. These clearly do not involve the lens as no lens is used but are rather artifacts related to the way in which color information is sampled and encoded. Could it be this that we are talking about in this thread?

Paul Curtis · February 20th, 2006, 01:51 PM

As has been touched on before, most lenses exhibit CA to some degree and with these 1/3" sensors the problem will be magnified greatly. If you think about how much a set of digiprimes go for *and* even they probably aren't high enough resolution to form an HD sized image at 1/3" sensor size.

Even on full frame or APS sized stills sensors you easily get CA, and that's with canon 'L' glass. (it's funny but in the stills world most people are obessive about whether a lens is 'good' or 'bad' and go through many replacements to find one they're happy with, i would imagine the same QA standards apply here too, maybe 2 replacements isn't enough)

In this particular case it's a question of whether it's too much, i appreciate everyone's comments and research as this helps me to work out whether i'll head down the HDV route or skip it.

But to add something constructive (i hope): on a lot of stills/raw processors there are options to help tweak the CA by scaling the RGB channels differently. Isn't there a workflow out there that could be used to help 'reduce' these effects on HDV?

I've always believe the bane of HDV to be optical glass. I really don't see an easy way out of this...

paul

Jack Foley · February 20th, 2006, 02:09 PM

A. J. deLange, I think what you are seeing there is simply the MPEG 4:2:0 compression of HDV. That has nothing to do with CA itself. But it may even enhance the effect.

What I am waiting for is till Canon offers the XL H1 body kit seperately. Then get a G35 (http://www.cinemek.com/) with the new relay lense they are working on and that should be available in a few months.

With this setup CA will be reduced almost totally I think if they make the relay lense right.

Jack

David Mills · February 20th, 2006, 04:28 PM

Quote:

Originally Posted by Barlow Elton

Hi David,

Oh yeah, it's there. I think I might have heightened it by adding a +2 color gain. I put up the CarlosDiego clip and it's ever so slight, but I think it's there too.

www.homepage.mac.com/mrbarlowelton

I think you're fine overall, but you might want to shoot flat for maximum latitude in post. Man, the CA would be the least of your concerns if the content's there. My low light footage has been phenomenal. You saw the "misc.Sundance2 clip", no CA. I have lit shots at slight tele that don't have the issue at all, and I bet a lot of your CU's will be max tele, if your going to use the 20x lens.

I think my advice would be to not push the color at full wide-angle. That's where I've seen the issue under specific circumstances.

It could be that the H1 is so damn sharp that it can't help but to have a little CA. I do know that it pixel shifts to achieve a full raster 1920x1080 SDI output...probably with the green pixels, so that might be contributing to the problem in some way.

David, I wouldn't worry so much. You'll get beautiful results, just watch for obvious contrasts (dark foregroud object, white background) and check for the anomaly. I doubt you're going to have any showstopping problems.

Thanks Barlow. Today I bit the bullet and decided to concentrate on content over form.Such a hard balancing act at this end of the market. Thanks for your help.

Barlow Elton · February 20th, 2006, 05:13 PM

Good luck David! Making a film is like going to war...at least you've got a very nice weapon at your disposal.

Please keep us posted, more than a few of us are very interested to learn of your experiences.

Barlow

A. J. deLange · February 20th, 2006, 06:10 PM

Quote:

Originally Posted by Paul Curtis

Isn't there a workflow out there that could be used to help 'reduce' these effects on HDV?
paul

Yes, there is a software package out there that one calibrates somehow (I've never used it) to obtain a set of coefficients descriptive of the CA of the lens. The software then radially scales the R, G and B images separately to reduce the lateral component of CA. To use this with video one would have to export the individual frames as JPEGs, do the processing and then put them back together as a movie. One would also have to calibrate for multiple focal lengths and perhaps focus distances.

John Jay · February 21st, 2006, 10:22 AM

The Green/Magenta fringing is indeed CA and can be accommodated in After Effects by scaling R&B channels - 99.6% is a good starting point

The Blue ghosting can not be fixed in post

I believe both are a symptom of the prism / CCD microlens interface and purchasing a body only option if it becomes available will help you none.

Paul Curtis · February 21st, 2006, 11:41 AM

>The Green/Magenta fringing is indeed CA and can be accommodated
>in After Effects by scaling R&B channels - 99.6% is a good starting point

I don't think it's as simple as that though. This will only correct lateral CA however i suspect that there's also a lot of longitudinal CA which means the different wavelengths of light are focused at differing planes. Plus add to the mix the possibility of sensor alignment problems and whateverelse might be involved then the solution is more complex.

The best approach is to correct what you can (as you say) and then use post to reduce the visual colour effects of the other abberations. The green/luma channel is the master and the eye is pretty forgiving so long as it's not bright green/magenta/blue.

Maybe everyone does this already in post with these 1/3" cameras?

cheers
paul

John Jay · February 21st, 2006, 01:20 PM

The above will cure 80% of the CA as I have indicated

If you wish to clear out the rest which is mainly in the overscan area you will need to apply cosine-fourth scaling ( cosine raised to the power of 4 ).

William Gardner · February 22nd, 2006, 09:07 AM

Hi Everybody,

I just posted a VirtualDub filter which will allow you to do the independent R,G,B, scaling for Chromatic Aberration correction without having to do individual frame exporting, correcting still-image-by-still-image, etc., as described above. You can find it here.

http://www.dvinfo.net/conf/showthread.php?t=61274

Hope some of you find it useful.
Cheers,
Bill

Lauri Kettunen · February 24th, 2006, 02:40 PM

Getting back to Michael's original concern, now once having more experience of the XL H1, I've started to suspect, that there's not necessarily something wrong with the camcorder Michael had. Instead, one does end up in certain situations with such an effect.

Before getting to this issue in more depth, I would like to add, that a similar kind of phenomena can be found with the XL2 as well. (I've viewed recently about hundred of hour of footages I took with the XL2 in about a year.) In fact, I've found also that my old Betacam SP tapes suffer occasionally for the same problem.

It seems that the critical issue is a sudden change from dark to bright colors, such as a shiny reflection of light next to something dark. In my case, whenever I've had a bright background sky and some dark object in the front, the border between the bright and dark is like a magneta or green line. However, in case of XL2 I can remember noticing something odd in the EVF while taking such shots, whereas in case of XL H1 the purples and green lines appear unexpectedly --and typically close to the corners of the image.

It seems one can avoid, at least in some cases, such artifacts by selecting a less steep gamma curve, setting the custom preset knee=low, and by carefully keeping the exposure low enough. If my experience is not misleading, it's better to keep the exposure rather low with HDV. For example, yesterday I shot trees having bright white load of snow in front of deep blue sky. If I tried to set the exposure to end up highlights with bright whites -zebra was set to 95, and the exposure was set just below that- then the purples and greens also appeared. But, setting the exposure lower removed the problem. This seems to suggest it better to shoot bit dark footages, and brighten them up in post.

In my experience HDV and the XL H1 seems to be quite a lot more challenging to use than DV cameras and the XL 1 or XL2. Especially, a "go and shoot" approach easily yields unpleasing results.

Roman Teufel · March 7th, 2006, 11:06 AM

Hi folks,
the chromatic aberration with the XL-H1 stock lens is certainly not tolerable for a camcorder like this, especially from a lens manufacturer like Canon. I have tested my own H1 with several EF 35mm lenses and there is not a bit of color fringing to discover. So even the old Canon SD 3x zoom 3.4-10.2mm has a lot less color fringing than the so praised new HD-20x lens.
But nevertheless since also the other 1/3 inch HD-cameras suffer from this lack, there is a little help by correcting the color shift in the postproduction. If you work with Final Cut Pro, there is a little plugin from River Rock Studios calles "Cheap Lens"

http://www.riverrockstudios.com/rive...cheapLens.html

As the name says the plugin for FCP normally is used to generate color fringing as an effect. The good thing is, that you can easily reverse the effect by a fingertip to eliminate nearly completely your chromatic aberration.
I treated a whole 60 minutes TV-documentary which was filmed with the Sony FX-1 so in the end there was no visible color fringing at all.
The only bad thing is the fact, that it consumes render time which normally should be used for more creative things.
But the only alternative would be to buy a HDCAM.

Hope it helps for most of you.

Regards
Roman Teufel
www.rtv-studio.de

Lauri Kettunen · March 8th, 2006, 12:20 AM

Quote:

Originally Posted by Roman Teufel

Hi folks,
I have tested my own H1 with several EF 35mm lenses and there is not a bit of color fringing to discover.

My experience also seconds that there is less problems with the EF lenses than with the stock 20x lens. For some reason the camera still prompts the EF lenses are HD incompatible when the EF-adapter is in use. My EF-lenses generate images with higher contrast than the 20x lens, but besides that have not observed other issues. I'm not so sure about the 3x lens. I've taken some akward examples.

The problem may have to do also with wide angles, which tend to generate more small details into the image. Typically, as the EF-lenses are huge telescopes with the XL H1, and consequently, the images tend to have less small and tiny details.

Nevertheless, setting cine=1 or 2,knee=low, keeping brightest areas below IRE=90-95, and avoiding color saturation seems to remove somewhat the problem of magenta and green borders. The borders between dark and bright areas are where the difficulties seem to be generated.

February 19th, 2006, 06:49 PM	#46
David Mills New Boot Join Date: Jan 2006 Location: Stockton on Tees,UK Posts: 21	purple and green borders are killing me Barlow I just looked at your slo mo trampoline again. Have a look at the trees on the right. That green fringe is what I am getting. Whoah that's bad. On the other hand the slow mo is great.

February 19th, 2006, 07:07 PM	#47
Barlow Elton Major Player Join Date: Mar 2005 Location: UT Posts: 945	Hi David, Oh yeah, it's there. I think I might have heightened it by adding a +2 color gain. I put up the CarlosDiego clip and it's ever so slight, but I think it's there too. www.homepage.mac.com/mrbarlowelton I think you're fine overall, but you might want to shoot flat for maximum latitude in post. Man, the CA would be the least of your concerns if the content's there. My low light footage has been phenomenal. You saw the "misc.Sundance2 clip", no CA. I have lit shots at slight tele that don't have the issue at all, and I bet a lot of your CU's will be max tele, if your going to use the 20x lens. I think my advice would be to not push the color at full wide-angle. That's where I've seen the issue under specific circumstances. It could be that the H1 is so damn sharp that it can't help but to have a little CA. I do know that it pixel shifts to achieve a full raster 1920x1080 SDI output...probably with the green pixels, so that might be contributing to the problem in some way. David, I wouldn't worry so much. You'll get beautiful results, just watch for obvious contrasts (dark foregroud object, white background) and check for the anomaly. I doubt you're going to have any showstopping problems. Last edited by Barlow Elton; February 20th, 2006 at 01:02 AM.

February 20th, 2006, 01:51 PM	#49
Paul Curtis Major Player Join Date: Mar 2005 Location: canterbury Posts: 411	CA in general, Post 'fixing'? As has been touched on before, most lenses exhibit CA to some degree and with these 1/3" sensors the problem will be magnified greatly. If you think about how much a set of digiprimes go for and even they probably aren't high enough resolution to form an HD sized image at 1/3" sensor size. Even on full frame or APS sized stills sensors you easily get CA, and that's with canon 'L' glass. (it's funny but in the stills world most people are obessive about whether a lens is 'good' or 'bad' and go through many replacements to find one they're happy with, i would imagine the same QA standards apply here too, maybe 2 replacements isn't enough) In this particular case it's a question of whether it's too much, i appreciate everyone's comments and research as this helps me to work out whether i'll head down the HDV route or skip it. But to add something constructive (i hope): on a lot of stills/raw processors there are options to help tweak the CA by scaling the RGB channels differently. Isn't there a workflow out there that could be used to help 'reduce' these effects on HDV? I've always believe the bane of HDV to be optical glass. I really don't see an easy way out of this... paul

February 21st, 2006, 10:22 AM	#54
John Jay Major Player Join Date: Sep 2002 Location: US & THEM Posts: 827	The Green/Magenta fringing is indeed CA and can be accommodated in After Effects by scaling R&B channels - 99.6% is a good starting point The Blue ghosting can not be fixed in post I believe both are a symptom of the prism / CCD microlens interface and purchasing a body only option if it becomes available will help you none. __________________ John Jay Beware *PLUGGER-BYTES*

February 21st, 2006, 01:20 PM	#56
John Jay Major Player Join Date: Sep 2002 Location: US & THEM Posts: 827	The above will cure 80% of the CA as I have indicated If you wish to clear out the rest which is mainly in the overscan area you will need to apply cosine-fourth scaling ( cosine raised to the power of 4 ). __________________ John Jay Beware *PLUGGER-BYTES*

February 20th, 2006, 12:23 PM	#48
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	It just occured to me that everyone concerned over this issue ought to turn on the color bars, record them to tape and capture a frame. I've posted a frame at http://www.pbase.com/agamid/image/53638038 for those who want to see immediately what to expect. The point is that there are pixel (or more) wide transition zones between color bars. These clearly do not involve the lens as no lens is used but are rather artifacts related to the way in which color information is sampled and encoded. Could it be this that we are talking about in this thread?

February 20th, 2006, 02:09 PM	#50
Jack Foley Regular Crew Join Date: Jan 2006 Location: Vienna, Austria Posts: 42	A. J. deLange, I think what you are seeing there is simply the MPEG 4:2:0 compression of HDV. That has nothing to do with CA itself. But it may even enhance the effect. What I am waiting for is till Canon offers the XL H1 body kit seperately. Then get a G35 (http://www.cinemek.com/) with the new relay lense they are working on and that should be available in a few months. With this setup CA will be reduced almost totally I think if they make the relay lense right. Jack

February 20th, 2006, 05:13 PM	#52
Barlow Elton Major Player Join Date: Mar 2005 Location: UT Posts: 945	Good luck David! Making a film is like going to war...at least you've got a very nice weapon at your disposal. Please keep us posted, more than a few of us are very interested to learn of your experiences. Barlow

February 21st, 2006, 11:41 AM	#55
Paul Curtis Major Player Join Date: Mar 2005 Location: canterbury Posts: 411	>The Green/Magenta fringing is indeed CA and can be accommodated >in After Effects by scaling R&B channels - 99.6% is a good starting point I don't think it's as simple as that though. This will only correct lateral CA however i suspect that there's also a lot of longitudinal CA which means the different wavelengths of light are focused at differing planes. Plus add to the mix the possibility of sensor alignment problems and whateverelse might be involved then the solution is more complex. The best approach is to correct what you can (as you say) and then use post to reduce the visual colour effects of the other abberations. The green/luma channel is the master and the eye is pretty forgiving so long as it's not bright green/magenta/blue. Maybe everyone does this already in post with these 1/3" cameras? cheers paul

February 22nd, 2006, 09:07 AM	#57
William Gardner Major Player Join Date: Feb 2005 Location: San Diego, CA Posts: 216	Hi Everybody, I just posted a VirtualDub filter which will allow you to do the independent R,G,B, scaling for Chromatic Aberration correction without having to do individual frame exporting, correcting still-image-by-still-image, etc., as described above. You can find it here. http://www.dvinfo.net/conf/showthread.php?t=61274 Hope some of you find it useful. Cheers, Bill

February 24th, 2006, 02:40 PM	#58
Lauri Kettunen Major Player Join Date: Aug 2004 Location: Kangasala, Finland Posts: 445	Purples and Greens Getting back to Michael's original concern, now once having more experience of the XL H1, I've started to suspect, that there's not necessarily something wrong with the camcorder Michael had. Instead, one does end up in certain situations with such an effect. Before getting to this issue in more depth, I would like to add, that a similar kind of phenomena can be found with the XL2 as well. (I've viewed recently about hundred of hour of footages I took with the XL2 in about a year.) In fact, I've found also that my old Betacam SP tapes suffer occasionally for the same problem. It seems that the critical issue is a sudden change from dark to bright colors, such as a shiny reflection of light next to something dark. In my case, whenever I've had a bright background sky and some dark object in the front, the border between the bright and dark is like a magneta or green line. However, in case of XL2 I can remember noticing something odd in the EVF while taking such shots, whereas in case of XL H1 the purples and green lines appear unexpectedly --and typically close to the corners of the image. It seems one can avoid, at least in some cases, such artifacts by selecting a less steep gamma curve, setting the custom preset knee=low, and by carefully keeping the exposure low enough. If my experience is not misleading, it's better to keep the exposure rather low with HDV. For example, yesterday I shot trees having bright white load of snow in front of deep blue sky. If I tried to set the exposure to end up highlights with bright whites -zebra was set to 95, and the exposure was set just below that- then the purples and greens also appeared. But, setting the exposure lower removed the problem. This seems to suggest it better to shoot bit dark footages, and brighten them up in post. In my experience HDV and the XL H1 seems to be quite a lot more challenging to use than DV cameras and the XL 1 or XL2. Especially, a "go and shoot" approach easily yields unpleasing results.

March 7th, 2006, 11:06 AM	#59
Roman Teufel Tourist Join Date: Feb 2006 Location: Aichhalden Germany Posts: 4	Help for chromatic aberration Hi folks, the chromatic aberration with the XL-H1 stock lens is certainly not tolerable for a camcorder like this, especially from a lens manufacturer like Canon. I have tested my own H1 with several EF 35mm lenses and there is not a bit of color fringing to discover. So even the old Canon SD 3x zoom 3.4-10.2mm has a lot less color fringing than the so praised new HD-20x lens. But nevertheless since also the other 1/3 inch HD-cameras suffer from this lack, there is a little help by correcting the color shift in the postproduction. If you work with Final Cut Pro, there is a little plugin from River Rock Studios calles "Cheap Lens" http://www.riverrockstudios.com/rive...cheapLens.html As the name says the plugin for FCP normally is used to generate color fringing as an effect. The good thing is, that you can easily reverse the effect by a fingertip to eliminate nearly completely your chromatic aberration. I treated a whole 60 minutes TV-documentary which was filmed with the Sony FX-1 so in the end there was no visible color fringing at all. The only bad thing is the fact, that it consumes render time which normally should be used for more creative things. But the only alternative would be to buy a HDCAM. Hope it helps for most of you. Regards Roman Teufel www.rtv-studio.de