Question about cirular rings when using a Variable Neutral Density Filter at DVinfo.net

Kajito Nagib · August 4th, 2011, 12:10 AM

i have a Light Craft Workshop 77mm fader ND MK2 which i use with my canon 7d. I noticed circular rings while filming the sky I didn't noticed it through my view finder but when i got back to my editing suite. is this normal for a ND filter or could the the lens be defective? I'm thinking of getting either a a Genus 77mm or a Singh-Ray but don't know if i'm going to run into the same problem.

Kajito Nagib · August 5th, 2011, 07:33 PM

I went out and did some test today and found out its not the ND fader or the lens. I filmed without any filters and I swap out the canon 17-55 for the Tokina lens 11-16mm and I'm still getting the same problem. I also noticed the the lines are not circular but various in shape and are more noticeable in the sky and when the camera is panning. I looked at old footage I shot last year and the same lines are in all my footage, don't know how I didn't notice it before.
I was always able to get around moire and aliasing but this is too much. A friend of mine said it may be H264 compression. Does anyone have a clue of what this is? Here are a few samples.
http://www.sweetproductionmedia.com/weird%20lines.jpg
http://www.sweetproductionmedia.com/weird%20lines2.jpg
http://www.sweetproductionmedia.com/weird%20lines3.jpg

Jon Fairhurst · August 5th, 2011, 07:44 PM

Those are contour lines. They happen on shallow ramps and subtle color changes when you don't have enough bits to describe the color details. Compression makes it worse, creating block artifacts.

DSLRs shoot 0-255. Your editing system probably converted it to 16-235, which involves a multiply. You might try putting your NLE in 32 or 16 bit mode, if available. Also, you can try adding some very light noise, which will help hide the effects of the multiplication and truncation.

August 4th, 2011, 12:10 AM	#1
Kajito Nagib Major Player Join Date: Jan 2007 Location: NYC Posts: 432	Question about cirular rings when using a Variable Neutral Density Filter i have a Light Craft Workshop 77mm fader ND MK2 which i use with my canon 7d. I noticed circular rings while filming the sky I didn't noticed it through my view finder but when i got back to my editing suite. is this normal for a ND filter or could the the lens be defective? I'm thinking of getting either a a Genus 77mm or a Singh-Ray but don't know if i'm going to run into the same problem. __________________ -kAj http://www.sweetproductionmedia.com/

August 5th, 2011, 07:33 PM	#2
Kajito Nagib Major Player Join Date: Jan 2007 Location: NYC Posts: 432	Re: Question about cirular rings when using a Variable Neutral Density Filter I went out and did some test today and found out its not the ND fader or the lens. I filmed without any filters and I swap out the canon 17-55 for the Tokina lens 11-16mm and I'm still getting the same problem. I also noticed the the lines are not circular but various in shape and are more noticeable in the sky and when the camera is panning. I looked at old footage I shot last year and the same lines are in all my footage, don't know how I didn't notice it before. I was always able to get around moire and aliasing but this is too much. A friend of mine said it may be H264 compression. Does anyone have a clue of what this is? Here are a few samples. http://www.sweetproductionmedia.com/weird%20lines.jpg http://www.sweetproductionmedia.com/weird%20lines2.jpg http://www.sweetproductionmedia.com/weird%20lines3.jpg __________________ -kAj http://www.sweetproductionmedia.com/

August 5th, 2011, 07:44 PM	#3
Jon Fairhurst Inner Circle Join Date: May 2006 Location: Camas, WA, USA Posts: 5,513	Re: Question about cirular rings when using a Variable Neutral Density Filter Those are contour lines. They happen on shallow ramps and subtle color changes when you don't have enough bits to describe the color details. Compression makes it worse, creating block artifacts. DSLRs shoot 0-255. Your editing system probably converted it to 16-235, which involves a multiply. You might try putting your NLE in 32 or 16 bit mode, if available. Also, you can try adding some very light noise, which will help hide the effects of the multiplication and truncation. __________________ Jon Fairhurst