Negative Gain...

D

DVX100Shooter

Veteran
I shoot on a negative 3 gain on my ENG camera at work and my co-workers are always saying how good the stuff I shoot looks. I noticed there is no negative gain on our cameras though. But is there a way to improvise? I do know that the XL1 has a option to shoot on a negative gain. You would think that there would be noise in the picture but it really is a nice picture. I use set up cards on my BetaSX camera along with the -3 gain.
 
Re: Negative Gain...

[quote author=DVX100Shooter link=board=Events;num=1089072516;start=0#0 date=07/05/04 at 17:08:35]I shoot on a negative 3 gain on my ENG camera at work and my co-workers are always saying how good the stuff I shoot looks. I noticed there is no negative gain on our cameras though. But is there a way to improvise? I do know that the XL1 has a option to shoot on a negative gain. You would think that there would be noise in the picture but it really is a nice picture. I use set up cards on my BetaSX camera along with the -3 gain.

[/quote]

Negative gain originally was a reduction of electrical potential to the image tubes in a tubed camera. In a CCD camera it is electronic procedure that reduces the pixel luminance in the camera logic.

There is no real reason why negative gain should make your pictures look better. Positive gain adds noise (actually, increases the noise compared to signal.) Negative gain does not usually result in less noise in cameras I am familiar with.

One reason why your pictures may look better is depth of field. Smaller depth of field is often seen by the eye as more natural and a "better composition." So it is possible that you are merely working at a larger iris, and thus at smaller depths of field than your coworkers.
 
Re: Negative Gain...

Negative gain forces the cam to set for larger appertures, if the output IRE has to be kept. This not only reduces depth of field but also reduces the noise levels: more light on the CCD means a higer S/N ratio.
 
Re: Negative Gain...

[quote author=andre link=board=Events;num=1089072516;start=0#2 date=07/06/04 at 14:09:03]Negative  gain forces the cam to set for larger appertures, if the output IRE has to be kept. This not only reduces depth of field but also reduces the noise levels: more light on the CCD means a higer S/N ratio. [/quote]

This is possible, except that CCDs are normally designed for a given maximum light range (which negative gain allows your to exceed). I am not sure on the average camera, if the difference in S/N would exceed the noise in the system encoding and thus be noticeable.

Mind you, the theory you present is correct. One area it may be noticeable is if you black stretch, where low light noise causes marching ants and dot crawl.
 
Re: Negative Gain...

You are right Slapdragon, one can overload the CCD. Thats why modern prosumer cams seldon offer this feature: they have very precise overload processing circuits (knee processing...) which could be fooled by reducing the reference gain too much. But the noise reduction (e.g.for large screen projection) can be important.
 
Re: Negative Gain...

[quote author=andre link=board=Events;num=1089072516;start=0#4 date=07/07/04 at 02:21:44]You are right Slapdragon, one can overload the CCD. Thats why modern prosumer cams seldon offer this feature: they have very precise overload processing circuits (knee processing...) which could be fooled by reducing the reference gain too much. But the noise reduction (e.g.for large screen projection) can be important. [/quote]

Excellent point. And manual knee is one of the reasons studio cameras look so good under the right hands.
 
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