"Dancing" noise problem at DVinfo.net

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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old April 13th, 2008, 09:21 PM   #1
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"Dancing" noise problem

Hi all,

I'm turning to the experts of this forum to hopefully shed some additional light on a noise problem with my Canon XH A1.

I'm shooting instructional videos on how to assemble, tune and use woodworking machinery. Whenever I film something black, like a power switch, knobs, or plastic covers, I end up with a lot of noise in the black areas only (actually, I can see the pixels "dancing"). Of course, everything is lit properly with studio lighting, gain at 0db, and I shoot fully manual with my aperture set to around 2.4, 2.8 or 4.0 max (1/60sec and 60i).

The problem is this "dancing" noise on the black areas which is very obvious only on my 26" Samsung LCD TV which I use as my CC monitor (it's hooked up to my computer with a HDMI cable). The same footage on my Samsung SyncMaster 206BW computer monitor isn't that bad, actually, I'm not even sure I can see it.

I tried burning a DVD (which has been downsampled to SD) so I can watch it on my CRT TV in the living room. Once again, I can't see it on my CRT TV but on the Samsung LCD TV, the SD sample is still noisy in the black spots.

The only reason why I'm stressing about it it's because I want to make sure my HD footage won't have that problem once it's ready to be release in full HD (the initial delivery will be in SD to comply with the market right now).

Of course, I also want to learn how to minimize this effects, I've got a few shorts scheduled for the coming months and I'd like to have that problem taken care of.

Here are the two samples showing the problem. The first one is the original clip coming from the camera (no filtering). The second clip is downsampled with Sorenson Squeeze to the SD format. None of those 2 clips have been rendered or modified in any way. It's a 15sec clip showing the ON/OFF switch with no movement at all. Let me know if you can see it too.

http://www.microbois.com/temp/TestTool.m2t (50 megs)
http://www.microbois.com/temp/TestTool_SD.mpg (10 megs)

I will appreciate any suggestions that may help me.

Best regards,


Benoit


P.S.: Does the secret lies in "crushing" the blacks? If so, how I do you do it with Vegas?
Benoit Bissonnette is offline   Reply With Quote
Old April 13th, 2008, 09:43 PM   #2
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You can try adjusting your gain settings.

Many feel that the A1's 0 gain is actually higher...closer to +3 which will tend to add noise to dark areas.

You can go into the menu on the A1 - Camera Setup / Gain Settings /:

Change Gain L to -3.

Give that a shot.

By the way, at least on my monitor, I could barely see the noise you are referring to. I had to strain to see it.

Hope that helps.
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Old April 13th, 2008, 10:51 PM   #3
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I think it might be your monitor. I don't see it at all. The image is clear and quite well lit.
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Old April 13th, 2008, 11:44 PM   #4
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I agree. I couldn't see anything out of the ordinary.
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Old April 14th, 2008, 08:40 AM   #5
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Thanks for your help, guys.

This is strange... I'm wondering if this problem will only show on those nice big plasma and LCD HDTVs only which are usually brighter than computer monitors.

The contrast ratio on my Samsung LCD TV is 4000:1 and 3000:1 on my computer monitor. Is this possible the problems lies in those values? Would it be possible that the noise is introduced or actually "amplified" and made more visible by the TV itself?

To answer Marcel, I did try reducing the gain to -3dB but didn't see anything different.

Thank you very much again for your help!

Best regards,


Benoit
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Old April 14th, 2008, 09:14 AM   #6
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I see it. If you are using a preset, try shooting it flat.
Also try overexposing the shot by one or two notches using the iris ring.
If there will be no movement and you are on a tripod, try a slower shutter speed. I use all of these methods to reduce noise.
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Old April 14th, 2008, 09:52 AM   #7
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Hi Eric,

I'm glad you are also seeing what I'm seeing... I was seriously wondering if I was getting too fussy.

I will try what you have suggested but as far as the custom preset is concerned, what would I need to change to shoot it "flat"? I'm not 100% sure of what's behind every settings in there and I'm still learning the craft...

Best regards,


Benoit
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Old April 14th, 2008, 11:35 AM   #8
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flat would be no preset at all with white balance or color temp tweaking only.
color correction would be done later in post.

if you shot that sample with a preset, just try overexposing it by one notch.
i think it would clean it up a bit.

use magnify on the lcd to check the pixles. in most cases you can see them dancing before you even take the shot.
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Old April 15th, 2008, 09:05 AM   #9
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Grain

Hi

What you see is grain. The XH A1 camcorder shows grain almost anywhere in the picture if you study it carefully. Even in broad daylight it produces grain in some areas of the picture. It's probably too small to se on an ordinary CRT TV but blown up on a plasma screen it shows up, and also on computer screens where you sit close. There might be settings to reduce the grain but to get rid of it to 100%, I don't think that's possible without loosing other qualitys of the picture.

Regards,

/Bo
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Old April 16th, 2008, 04:27 PM   #10
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You could try the neat video noise reduction suppression. We tend to use that on pretty much all dimly lit footage. I'm sure it would work on the dark areas you describe as well.
Andy
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