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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 7th, 2008, 03:19 PM   #1
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Auto Gain Control

Is there any disadvantage to using Auto Gain Control?

I am practicing using Manual settings but seems that Auto Gain Control is working great, just not sure if there are times its a disadvantage.
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Old March 7th, 2008, 04:00 PM   #2
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I just finished filming an indoor event where the lighting from nearly every square of the building changed. I used the Auto Gain control indoors and found that I got a lot of noise in the lesser lighted areas and perfectly clear in the well lit areas. I'm not sure if there's something else I should be doing or not, but I was actually on the board just now to ask whether I did something wrong with my A1 to get so many shots with grainy marching ants when on auto gain control. It is definitely a weird look when I'm shooting a continuous shot as I'm walking and the people have snowy microdots of noise on them (usually dark clothes) and then when we get into a different (brighter) light situation, it clears up without a problem.
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Old March 7th, 2008, 11:40 PM   #3
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Uh
AGC will not adjust F stops, when using AGC, if there is really bright background light, your subject may becomes dark since the AGC compensate for the greater light source.
Using AGC in variable lited areas, you may like to adjust F stop accordingly, ie, lower(open) F in dark area and increase(close)F in lited areas and let the AGC micromanages the finer detail of the amount of light; then again, refer to first part. Hope this help.
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Old March 7th, 2008, 11:48 PM   #4
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Quote:
Originally Posted by Tung Pham View Post
Uh
AGC will not adjust F stops, when using AGC, if there is really bright background light, your subject may becomes dark since the AGC compensate for the greater light source.
Using AGC in variable lited areas, you may like to adjust F stop accordingly, ie, lower(open) F in dark area and increase(close)F in lited areas and let the AGC micromanages the finer detail of the amount of light; then again, refer to first part. Hope this help.
Thanks, I have my gain controls set at +3, 0, -3 and sometimes that is not enough, its either go to AGC, or leave the scene dark. I have learned to leave the scene a little dark when at receptions, results are pretty good and its suppose to be dark anyways. Sometimes I find myself trying to get a perfect exposure when its suppose to be low light.
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Old March 8th, 2008, 03:33 AM   #5
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Using AGC (and forgetting it is on) is the number one reason people get bad video from XH-A1. You close the aperture to adjust the picture, AGC compensates adding gain and causing grain and noise.

Basic rule: never use AGC
Advanced rule: after you thoroughly understand what each adjustement does and can not get results without using AGC, use it, but remember to turn it off!

I have the gain set at -3, 0 and +3 or +6. Never higher. Underexposed looks better than the pulsating grid compression artefact I get from +12 gain produced noise.
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Old March 9th, 2008, 04:03 PM   #6
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Totally agreed, never use AGC.
set it up to -3, 0, +3 unless it really is dark and then push it up to +6 if you really need too.

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Old March 9th, 2008, 04:26 PM   #7
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Totally agreed, never use AGC.
set it up to -3, 0, +3 unless it really is dark and then push it up to +6 if you really need too.

Jon
Well I still have to do the post work, but I had to use AGC last night, I fight it as much as I can. The reception was so dark even at -6 at 1/30 just way to dark and the video lights only work so far. The DJ's lights were not helping and really causing havok with exposures. I finally put it on AGC until the festivites were confined to the smaller dance floor, where the video lights could give me enough light to shoot at +6 and +3 at time depending on what the DJ was doing.

From first glance all the footage will be usable, I did shoot the second camera at +6 and not use AGC just kept everything close just in case the tripod mounted on AGC was too grainy.
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Old March 9th, 2008, 04:46 PM   #8
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Hope the footage works out for ya.

J
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