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Canon XH Series HDV Camcorders
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Old April 27th, 2008, 11:54 AM   #1
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What is Auto Up To?

double newbie here (to these boards and the A1).

I was filming in a badly lit venue and accidentally started in Auto mode. A few seconds later I switched it to Spotlight mode. Looking at what was captured, for the few seconds of Auto, the camera had put itself in a higher gain as the footage is quite grainy (see http://www.festivalpreviews.com/blog/images/auto.jpg). The Spotlight footage is much smoother (see http://www.festivalpreviews.com/blog.../spotlight.jpg).

Can anyone explain why Auto uses a higher gain than is obviously necessary?

TIA

Ian
www.festivalpreviews.com

Last edited by Ian Wright; April 27th, 2008 at 11:56 AM. Reason: urls wrong
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Old April 27th, 2008, 06:44 PM   #2
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Ian... Welcome to the wonderful world of the A1. I believe what happens when you use Auto mode is that everything goes auto. You might want to check the manual for details of what that entails. There is an auto gain setting which I've learned is something you want to avoid. Lock the gain down and use the switch (LMH) to adjust it. If you're shooting in a dark venue, you might want to make the presets 0, +3, +6 to give you some headroom. I leave mine set at -3, 0, +3, but I always shoot outside.

As an aside, depending upon what you are shooting in the dark, you might want to back the shutter down to 1/25 to give you more light to work with.
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Old April 29th, 2008, 07:37 AM   #3
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thanks for the welcome and the reply.

Both modes are auto setting the gain and I was really wondering why Auto essentially gets the wrong answer when Spotlight gets the right answer.

I've since successfully "graduated" to manual. You mention using a shutter of 1/25th. I'm on 50i mode, will that shutter speed not cause a problem? I'm currently using 1/100th. I guess I should suck it and see...

Thanks
Ian
http://www.festivalpreviews.com
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Old April 29th, 2008, 08:46 AM   #4
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Hi Ian. 1/50s is the normal shutter speed for 50i or 25F, but if the light is very low one of the things you can adjust is to set the shutter to 1/25s as mentioned by Tripp. It gives you double the light, but at the penalty of more motion blur. 1/100s (or faster) requires more light and gives more strobing, but can be useful if you intend to slow down the footage and want to keep it sharp.

Richard
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Old April 29th, 2008, 11:16 AM   #5
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auto exposure assumes that average tone of the image is mid gray - and in an image with a lot of black it will overexpose (with a lot of white it will tend to underexpose)

spotlight mode assumes that only the brighter parts of the image are important and it lets the black background stay black
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Old May 4th, 2008, 04:53 AM   #6
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As Ralph says, spotlight mode tends to expose for highlights (a bright area in an otherwise darkish image), while auto exposed for the overall average image and thus thinks the scene is darker, and often adds more gain and thus more visible grain.
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Old May 11th, 2008, 06:40 AM   #7
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thanks for the answers. sounds like Spotlight is a sort of intelligent spot meter mode.

Thanks

Ian
www.festivalpreviews.com
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Old May 11th, 2008, 10:16 AM   #8
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afaik - it's a center weighted meter rather than a spot meter
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