Edge noise on all channels

[Eric Horne]

Hey guys... new to the group, thanks for letting me in!

I am a hobbyist who happened to pick up a Canon XL2; the plan was to shoot youth sports but I've also been doing some indoor (dark) stage recording.

I've noticed on dark footage there there tended to be a blue haze on the left and right sides of the footage. Exploring this, I've discovered it is related to gain - anything above +3dB produces the haze. It exists on both sides on the blue channel, and much to my surprise only the left side on green and red.

In order to demonstrate this, I took a frame at low gain and differenced it against a frame taken at a high gain. I posted the pictures up here if you want to see them (apologies for the crude site). The blue is a little hard to pick up against the black, but if you look closely you'll see it. Red and Green clearly show the problem. All frames were shot in my dark garage.

I've sent the camera in to Canon to fix this issue, they returned it (with a broken zoom) without apparently addressing this. Before I send it back to Canon for repair, does anyone have any thoughts on what might be wrong -- or even if this is wrong? (perhaps it's just the way the camera works).

In this case, I'm shooting 24p in low light with high gain (6db and over) at 16:9 aspect ratio. I don't know if this happens at 4:3. I'm pretty sure it happens at 30p as well (haven't tried 60i).

I appreciate any advice you folks might have about how I can correct this myself, or what words to use with Canon to convince them there is a problem (if there is one!)

Thank you!

[Chris Soucy]

Scroll to the bottom of the page and type "XL2 Gain Noise" into the Google box (other word structures will give different results which you may wish to try).

A wealth of info there.


CS

[Eric Horne]

Thanks, Chris for the response. I looked through all the forums and I did what you suggest; you are right, there is a ton of great information about gain and SNR. In fact, I got an answer to a question I had about the -3db setting on the camera.

However, nothing that I saw mentions anything about increased noise on only the left and right edges. The center, say 85% of my frames are noise free and nice; but the left and right 7.5% (or so) of the edge increasingly get noisier the closer you get to the edge of the frame. And I only have this problem at +6db and beyond. It's like a fast degrading non-linear degradation in SNR -- almost a vignetting effect, but with noise instead of luminosity and only left/right (top/bottom is perfectly clear, except of course the corners). I'd attach a file, but I can't see how to do that here.

So while I appreciate your kind pointer, I didn't quite find what I'm looking for -- except that perhaps not finding it tells me I have some kind of problem, I suppose.

[Chris Soucy]

if it ain't on these boards, it ain't happened, usually.

Guess Canon Service is the next place to try.

Make sure you supply adequate documentation to back up your complaint.

Good luck.


CS