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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 March 28th, 2007, 10:28 PM   #1
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Low Noise in Spotlight Mode

I am wondering how the spotlight mode achieves such low noise. Sometimes you don't need to resolve shots in dark areas. You just want them to be dark and clean. So how does the spotlight mode achieve dark shots with such low noise? Can it be duplicated in other standard modes?

-Jonathan
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Old March 28th, 2007, 10:39 PM   #2
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Hi Jonathan, my understanding of spotlight mode is that it uses a different metering process, which exposes only for the center of the image and simply ignores the surrounding areas (which keeps faces from blowing out; usually an evaluative metering will try to balance the entire frame, resulting in overexposed faces and noisy backgrounds). I've never tried to duplicate it in any of the other program modes but maybe somebody else has around here.
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Old March 28th, 2007, 11:39 PM   #3
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Yes but all metering aside (try in full manual mode any settings you wish) I can't get as noise free an image in any mode with any settings as I can with spotlight mode when there is next to no light. How is this done? It's a stark difference.
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Old March 29th, 2007, 11:33 AM   #4
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Hmm, I was able to replicate it using -3db Gain on Manual. Granted I was verifying using the magnification function. I did not have it hooked up to an HDTV.
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Old March 29th, 2007, 08:33 PM   #5
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Not sure about the A1, but the older XL1 and GL1 models use a bottom center weighted average metering scheme for normal exposure modes, and for SPOTLIGHT mode they used a "49-area-splitting evaluation photometry" scheme (7x7 zones). I suspect that it looks for the brightest zones and average meters on that zone. Thus the bright areas in the spot light receive a "correct" exposure, and that means the areas out of the spotlight would have less noise-producing exposure components (e.g., lower gain, faster shutter) and thus noise in the shadows would be less and shadows would be darker effectively more of a Black Press effect perhaps.

The A1 may use a similar system, possibly with more zones and there may be other image processing involved as well.
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Old March 29th, 2007, 09:09 PM   #6
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OK, but here's what I'm getting at (and I would like someone else to try this.) When I hook up my A1 to my HDTV through the included HD cable and preview the screen (in a fairly dimly lit living room) I can't reproduce the low amount of noise in Spotlight mode with any other mode by changing aperature, shutter or any other setting in that mode. Can somone else test this? Maybe there is a setting I'm missing that would allow me to reproduce? I get a pretty noisy shot in every other mode with the gain switch all the way down.

Last edited by Jonathan Gentry; March 29th, 2007 at 10:41 PM.
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Old March 29th, 2007, 10:54 PM   #7
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Hi Jonathan. Is it possible that your AGC switch is set to ON and that this is not active in spotlight mode? Just a thought.

Richard
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Old March 30th, 2007, 12:10 AM   #8
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Thank you sir. Yes the AGC button was on. I was thinking that this cam couldn't possibly be this noisy.

Problem solved...
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Old March 30th, 2007, 12:39 AM   #9
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Wow Richard...nice one.


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