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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 August 28th, 2007, 08:35 PM   #1
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Grains, pixels, and personal incompetence

Let me preface this post with a broad disclaimer: User error is the single most likely source of these problems. That being said, I've run across a few unwanted visual effects in some of the test footage I've shot.

I was using the 5296 preset found in the sticky thread above, and the standard gain settings (though I didn't mess with the gain, so it should be at the lowest of the standard settings). Also, I was shooting in 24f. My fstop, zoom, and shutter speed changed from time to time, as I was experimenting with different settings.

When shooting inside, even during the day with bright sunlight, I seem to be getting a grainy image. I've searched on the forums and I've seen people suggest changing the gain settings to 0 or even -3db. Can anyone comment on whether that actually reduces gain? If it does, what do you give up and how do you compensate for it?

When shooting outside, I notice some pixelation, particularly on the borders of strongly contrasting colors, like a black shirt on a white person. Is this normal? If not, what can I do to correct it?

Finally, my footage looks much worse on an HD tv than a SD one. I assume that's because the HD TV is able to more accurately display my incompetence than an SD one. What settings concerns do you have to keep in mind specifically for HD?

Thanks!
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Old August 28th, 2007, 09:01 PM   #2
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You don't happen to have the AGC switch on the side of the camera set to ON do you?
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Old August 29th, 2007, 07:24 AM   #3
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The grain effect is due in large part to slight differences in pixel dark current and sensitivity. It is most apparent in shadows areas of the image. Longer exposures can make dark current variations more apparent. Reducing gain has the effect of reducing the visibility of the differences in pixels. However, if reducing gain is accompanied by a corresponding slower shutter speed, the benefit may be reduced.
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Old August 30th, 2007, 05:55 AM   #4
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I do not have AGC on. Should I?
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Old August 30th, 2007, 07:26 AM   #5
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I do not have AGC on. Should I?
That is your decision. With AGC enabled, the camcorder controls the gain setting, and may increase gain in moderate-to-low light situations (or even in bright light situations if the ND filter is on) without your knowledge. This may make grain more apparent in the image. Many shooters prefer to manually control gain (and the other exposure parameters for that matter). You really need to work with the camcorder, experiment a lot, to see what works best for you in the different shooting situations you encounter.

Note that AGC is automatically ON in Night and Easy Recording modes, OFF with gain set to 0 dB in Spotlight mode, and can be on or manually adjusted in other recording modes..
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Old August 30th, 2007, 07:35 AM   #6
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no should not put agv on :-)

I experienced the same problem as you. My problem was that my LCD of the A1 was not properly calibrated out of the box.
I hooked it up to a tv screen and used that to calibrate it.
Since the LCD was displaying everything to bright I usually made my lense opening smaller and put the shutter to fast.
Once calibrated you should be able to reduce the grain by setting the lensopening and shutter speed to better values
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Old August 30th, 2007, 07:39 AM   #7
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Originally Posted by Jeff Yin View Post

When shooting inside, even during the day with bright sunlight, I seem to be getting a grainy image. I've searched on the forums and I've seen people suggest changing the gain settings to 0 or even -3db. Can anyone comment on whether that actually reduces gain? If it does, what do you give up and how do you compensate for it?

you compensate by adding artificial light, either your light kit or maybe a good on-camera light. or blocking the ambient light and either opening the aperture or adding a small amount of gain. or getting a good artificial light set up. if you shoot indoors using only natural light, you're typically introducing a range of contrasts which the camera doesn't necessarily have the latitude to handle (e.g. you have to choose, am i going to blow the highlights to get someone face properly exposed, or am i wanting a more evenly exposed image, therefore i'll settle for more shadows. et cetera).
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Old August 30th, 2007, 07:52 AM   #8
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If you were shooting at anything other than -3 or zero db, you're going to get grain. This is true with any camera. Shutter speed should be 1/48 for 24 fps, unless you're after an effect.
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Old August 31st, 2007, 03:23 PM   #9
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Thanks for the settings advice. I've shot some test footage and it looks much cleaner than when I started.

Does anyone have any input for the pixelation problem I noticed on external/outside shots?
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Old August 31st, 2007, 04:33 PM   #10
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Does anyone have any input for the pixelation problem I noticed on external/outside shots?
You might get better help if you post a pic or clip of the problem!
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