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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 4th, 2008, 07:21 AM   #1
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Is +6dB gain too much?

Hi all. last saturday night I shoot a party with my new A1 and as with all parties the light conditions were very bad. Using a lamp was not much appreciated so I shot most footage using the [A] recording program and the panalook preset with +3dB gain en some even with +6dB gain. Is it possible that because of that my video shows ... eeehhh how do you say that in English ... ghosting I think. I see moving persons kind of fading through the footage in stead of plain walking. Should I have used no gain and another shutterspeed or aperture maybe? Or is the only solutions for this conditions using some kind of videolight?
And is shooting in SD less critical then shooting in HD concerning these issues?
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Old March 4th, 2008, 07:47 AM   #2
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Quote:
Originally Posted by Kees van Duijvenbode View Post
Hi all. last saturday night I shoot a party with my new A1 and as with all parties the light conditions were very bad. Using a lamp was not much appreciated so I shot most footage using the [A] recording program and the panalook preset with +3dB gain en some even with +6dB gain. Is it possible that because of that my video shows ... eeehhh how do you say that in English ... ghosting I think. I see moving persons kind of fading through the footage in stead of plain walking. Should I have used no gain and another shutterspeed or aperture maybe? Or is the only solutions for this conditions using some kind of videolight?
And is shooting in SD less critical then shooting in HD concerning these issues?

Ghosting can occur from to low of a shutter speed and if you turn on some of the noise reduction features to high. I believe there is a low light preset in the library that people have had some very good luck with. I try to never break 3db but if you have to you have to. Always open the aperture as much as you can and lower the shutter speed as low as possible without ghosting issues but in the end, you have to either add light or boost the gain most of the time.
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Old March 4th, 2008, 11:07 AM   #3
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Were you shooting on a tripod with the stabilization on? That could cause a similar problem.

I've shot at +6 db before, at 24F, and a 1/48 shutter. I also used a 1/24 shutter for some even darker things with no blurring.
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Old March 4th, 2008, 01:50 PM   #4
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+6 dB gain is still usable, +12 dB is noisy and starts to cause checkerboard type artefacts with HDV compression. Ghosting, what was your shutter speed? If too long, spanning more than one field (1/50 in PAL) is starts to cause strange effects.
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Old March 4th, 2008, 06:20 PM   #5
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Noise reduction settings in the presets can cause ghosting.
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Old March 5th, 2008, 07:04 AM   #6
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OK. Thanks for the answers. I have to further investigate them all.
Yes, I was shooting from a tripod but I remember I thought about switching the stabilizer of after about 10 minutes. Have to check if I notice any difference.
Donn't know about aperture and shutter settings. I shot with the [A] program.
And I shot using the 12dB preset of Wolfgang which has NR1 on low and NR2 on middle.
So before my next wedding I have to test all the possible problems with low-light conditions.
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Old March 5th, 2008, 12:28 PM   #7
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I suggest shooting your tests in Tv mode, with the shutter speed at 1/50 and then 1/25. This way you will know what all the setting are and can adjust them to see the results.

If you are in Tv mode and push the Exp. Lock button the Iris (f stop) will also be in manual.
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Old March 5th, 2008, 02:12 PM   #8
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If by ghosting you mean you are seeing trails after moving objects in the frame, then it is very likely caused by the noise reduction. I use NR1 on low frequently, though, and the effect is not too obvious. NR2 supposedly doesn't cause this effect, but putting it on middle will certainly cause some softness, and I don't think you need this amount of noise reduction for 6db gain. Only you can say for sure - try some tests.

If what you are seeing is stuttery motion and motion blurring, then this isn't ghosting, but simply the effect of a very long shutter speed. I suspect that this is what you are getting, being on A mode. In effect, you don't have too much gain , but not enough (at least that's what the camera thinks.)

In any case, 6db should be fine, and 12db isn't too bad for SD party scenes. If the subject matter is compelling enough, nobody will notice. Don't go over 12db, though, unless you really, really need to.

High gain will give you grain, not ghosting.

I suggest you definitely use Tv mode, as suggested above. 1/50 sec is "normal", and 1/25 will work in low-light, as long as there isn't too much movement. You just want to avoid the situation where the camera sets a really slow shutter speed by itself.

It's difficult shooting parties without additional lights. You have to try and use whatever light you have as best you can. Get people to stand near the house lights when possible.

I'm not familiar with the preset you are using, but DON'T use VIVIDRGB in this situation, as it was intended for ample light. You could try it with the color gain dialed down, but you'll have to test it. Basically, for low light you might want to stretch the blacks, raise the setup level and maybe the pedestal. With the A1, adding some color gain might help, but not as much as the VIVID preset adds.

One big problem with dim lighting is that there isn't much color at all, so fancy color corrections in the camera aren't much use. Just set the white balance manually and you should be as good as you'll get, color-wise.

Happy shooting!
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