2 years and I got my first CA footage! Yes! at DVinfo.net

Marty Hudzik · May 19th, 2008, 01:55 PM

Sarcasm in the title obviously but I thought I would post this and see if I can get some input from my esteemed colleagues.

First let me preface this by saying that I have seen footage posted on the web of Chromatic Abberationi in XLh1 footage with the stock 20x lens. It was quite noticable. However, I have neer seen it on my XLh1 so I just thought I was lucky. My luck changed Saturday night.

I was shooting a choral concert for a local International Touring Choir. The event was in an auditorium and the lighting was straight up tungsten white. The stage was washed with it and there was no other colors present. While this is not the least bit interesting to see (not dramtaic at all) it was even and birght. I figured the video would come out super clean and sharp.

I normally shoot with the Steven Dempsey preset "panalook" which crushes the blacks and the setup level is down with additional color tweaks. For this event I wanted a "flat" pallette to color grade in post, so I used the default camera setup with just the knee adjusted to prevent blowouts. Additionally I hoped to match this to HV20 B-Roll camera in the balcony set to neutral for color.

It all went without a hitch but when I watch the footage the singers on either end of the stage are showing significant CA on their outer edges. They were wearing white shirts with red ties but the CA mostly appeared on the contrasty edges of their shirts and the dark curtain behind them.

I was zoomed about 50% or so most of the time, 24F and 1/48th shutter. The aperture was set between 4.8 and 5.6 for almost the entire event. I typically try to keep the iris significantly more open than this but figured I'd be okay. Any ideas what may have contirbuted to this? I wish I had the opportunity change some settings on the camera at the venue to verify if it was a setting that caused this or just these circumstances.

Thanks all. Just hoping to hear your insight on how to avoid this in the future.

Seun Osewa · May 19th, 2008, 03:14 PM

Fullres grabs or it didn't happen!

Les Howarth · May 21st, 2008, 04:12 AM

"contrasty edges of their shirts and the dark curtain behind them."

you said it right there, high contrast edges will always tend to highlight the shortcomings of any lens - and any codec too. If you are using a scene file that increases contrast then it is more likely to become obvious.

- Not a canon video guy (although I am on the still camera side) but this apples to all cameras and lenses to a greater or lesser degree.

Les H

Marty Hudzik · May 21st, 2008, 06:39 AM

I looked at the footage again with fresh eyes last night and it turns out it isn't nearly as bad as I thought. It really only appears on the far left side of the frame where the white shirts meet the black curtain behind them. Not bad at all really. I zoomed in on the right side of the frame and saw no CA at all so in hind sight I am thankful. I should also add that it was mainly visible on the computer LCD. I rendered out a 3 minute segment to blu-ray and watched it on my 46" LCD and it looked pristine. Had to strain to see any trace of CA at all, which it obviously still has....you just can't really see it unless you are looking for it.

Thanks all. I did grab a frame if anyone wants me to post it still....but I don't really see the purpose at this point.[/

Seun Osewa · May 21st, 2008, 07:02 AM

I would love to see the frame: I don't have the cam yet.

A. J. deLange · May 21st, 2008, 11:58 AM

Remember that there are other phenomena at edges which result in fringing. If it isn't symmetric with repect to the center of the frame and/or if you can't fix it with Photoshop's CA fixer it isn't CA.

May 19th, 2008, 01:55 PM	#1
Marty Hudzik Trustee Join Date: Jul 2004 Location: Canton, Ohio Posts: 1,771	2 years and I got my first CA footage! Yes! Sarcasm in the title obviously but I thought I would post this and see if I can get some input from my esteemed colleagues. First let me preface this by saying that I have seen footage posted on the web of Chromatic Abberationi in XLh1 footage with the stock 20x lens. It was quite noticable. However, I have neer seen it on my XLh1 so I just thought I was lucky. My luck changed Saturday night. I was shooting a choral concert for a local International Touring Choir. The event was in an auditorium and the lighting was straight up tungsten white. The stage was washed with it and there was no other colors present. While this is not the least bit interesting to see (not dramtaic at all) it was even and birght. I figured the video would come out super clean and sharp. I normally shoot with the Steven Dempsey preset "panalook" which crushes the blacks and the setup level is down with additional color tweaks. For this event I wanted a "flat" pallette to color grade in post, so I used the default camera setup with just the knee adjusted to prevent blowouts. Additionally I hoped to match this to HV20 B-Roll camera in the balcony set to neutral for color. It all went without a hitch but when I watch the footage the singers on either end of the stage are showing significant CA on their outer edges. They were wearing white shirts with red ties but the CA mostly appeared on the contrasty edges of their shirts and the dark curtain behind them. I was zoomed about 50% or so most of the time, 24F and 1/48th shutter. The aperture was set between 4.8 and 5.6 for almost the entire event. I typically try to keep the iris significantly more open than this but figured I'd be okay. Any ideas what may have contirbuted to this? I wish I had the opportunity change some settings on the camera at the venue to verify if it was a setting that caused this or just these circumstances. Thanks all. Just hoping to hear your insight on how to avoid this in the future.

May 19th, 2008, 03:14 PM	#2
Seun Osewa Major Player Join Date: Oct 2006 Location: West Africa Posts: 255	Fullres grabs or it didn't happen!

May 21st, 2008, 04:12 AM	#3
Les Howarth Regular Crew Join Date: Oct 2005 Location: Manchester England Posts: 40	"contrasty edges of their shirts and the dark curtain behind them." you said it right there, high contrast edges will always tend to highlight the shortcomings of any lens - and any codec too. If you are using a scene file that increases contrast then it is more likely to become obvious. - Not a canon video guy (although I am on the still camera side) but this apples to all cameras and lenses to a greater or lesser degree. Les H

May 21st, 2008, 06:39 AM	#4
Marty Hudzik Trustee Join Date: Jul 2004 Location: Canton, Ohio Posts: 1,771	I looked at the footage again with fresh eyes last night and it turns out it isn't nearly as bad as I thought. It really only appears on the far left side of the frame where the white shirts meet the black curtain behind them. Not bad at all really. I zoomed in on the right side of the frame and saw no CA at all so in hind sight I am thankful. I should also add that it was mainly visible on the computer LCD. I rendered out a 3 minute segment to blu-ray and watched it on my 46" LCD and it looked pristine. Had to strain to see any trace of CA at all, which it obviously still has....you just can't really see it unless you are looking for it. Thanks all. I did grab a frame if anyone wants me to post it still....but I don't really see the purpose at this point.[/

May 21st, 2008, 07:02 AM	#5
Seun Osewa Major Player Join Date: Oct 2006 Location: West Africa Posts: 255	I would love to see the frame: I don't have the cam yet.

May 21st, 2008, 11:58 AM	#6
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	Remember that there are other phenomena at edges which result in fringing. If it isn't symmetric with repect to the center of the frame and/or if you can't fix it with Photoshop's CA fixer it isn't CA.