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Old November 5th, 2005, 08:37 PM   #1
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gain question -3db

I have a question about the gain control on the XL1-s. What is the -3db gain for? I understand, if I'm right, that gain pushes the light through a electronic signal up on the camera so if a 0 gain is no added push of the signal then what is -3db? Does that electronically remove light from the CCDs and in doing so lower resolution? Or is it the setting to truly take all gain from the shot?

I guess what I'm asking is if I'm lighting and staging a shot and able to control my light with either, which one is going to give me the cleanest picture?

Brian Doyle

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Old November 6th, 2005, 01:33 AM   #2
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Do a test under your conditions and see what you like.
The -3 db setting can be used for control eg where you want the lense more open . I dunno I have shot with -3 and like the image ,it and 0 db do not reduce resolution nor add grain.I think either will typically give a clean shot.
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Old November 6th, 2005, 06:22 AM   #3
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The dB setting control the amount of gain (amplification) of the signal read off the CCD. Zero dB is the "standard" setting. -3 dB indicates the the signal amplification is reduced slightly, and should result in slightly less noise in an otherwise properly exposed image.

The reason is that the signal read off the CCD contains both the image data you want (light level hitting the pixels) and some noise that is intrinsic to the CCD pixels. To the amplifiers signal and noise are the same (a voltage) and are amplified equally. The -3dB gain setting requires the shooter to increase up the light reaching the CCD for the same image output from the amplifier, but the noise in the output image will be 3 dB lower.

This may not be important for many users, but some shooters find it valuable for their purposes.
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Old November 6th, 2005, 12:56 PM   #4
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Thanks Don,
I thought it was something like that. I did a lot of tests with both settings and the darker colors seem crisper but I was just wondering if I was fooling my eye. Either way I'm shooting with -3dB from now on as much as I can. Why not?
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