Video Gain
 

I have researched video gain on the web but still do not really understand how and when to use it. I have a Sony PD170 and have tested it shooting inside but did not see a difference. Can anyone explain to me how it is used?

thanks
Janice

Allow me to be academic. For a moment, think of Pure Black as "0" and Pure White as "10" in a perfect scale. All of the immeasurable shades of grey fall within "0" and "10". There is no discussion of color. In a perfect scene, the perfect balance between absolute black and absolute white is 5. For the human eye, the divisions of shift between black and white are, lets say, 20. Of those divisions, no camera can achieve more than 5. What the camera can see is significantly less than what the human eye can see. If you choose to set the camera's "5" value at "3", then anything above 5.5 is going to be white. Set the camera to "7", black is now "4.5". White is "9.5". White balance your camera at a specific f-stop at "0 gain" to establish "5".

The best quality images from any video camera are, by design, going to be achieved at "0" gain. This is the base line. Increase gain and the camera's ability to "see" expands. However, the expansion of light sensitivity is being compressed into the same basic 5 divisions, because that is all the camera can manage. The result is a shift in light values and color values. At some point the image breaks its connection with reality. I usually won't approach 12db gain without it being an absolute necessity. Every camera is diferent, so test bu pushing the limits. Increasing gain is going shift everything, from black/white/grey values to color shifts, and can result in unacceptable footage. Decrease gain to -3 (if that option is even available), and both light and color values intensify.

Many cameras offer automatic exposure compensation adjustments, which I feel are preferable approaches to adjusting exposure than gain settings.

Thanks Waldemar, great explaination. It sounds like you do use gain though. In what situations do you use it?

Waldemar did a great job explaining gain-as for when to use it, I use it when necessary. In other words at most wedding receptions they knock the lights down to the point where youliterally can not see so whether it's my DSR 250 or good old PD150 and a 35W light I usually end up kicking the gain to 9 to get a USEABLE image-notice I said useable. With out gain I still have an image but IMO not a good enough one to use so hence gain. How do I know, well experience plays a big part but I also adjust the gain until my iris at least starts to close so I know I'm getting some movement (usually about 12)then I back the gain off (usually 9). I'm generally going to be shooting at 1/60th at f/1.6. One thing about the Sonys even with gain they still look good. I've done stuff at 12, 15 and yes even 18 and at 18 is where it starts to go away but at 15 the image quality still held its own.
Like Wald says, less is better but sometimes you gotta give up a bit of quality to get a useable image. If you can't see a decent image in your VF or LCD (set the brightness DOWN to mimic the room) then you won't see one on tape either an dif your exposure is as far as it can go then it's time to use GAIN!
Don

Thanks Don. I will practice adjusting the settings in different dark settings. Good suggestion on the VF/LCD too. I really appreciate the help.

Janice

What Don said.

I hate using gain, but it is always necessary at one time or another ...particularly if you either can not use additional lighting or that lighting is limited.

One thing I like to do at a reception (when I can get away with it), is to bounce a tungsten quartz light off of a ceiling or photo umbrella reflector to cast fill over the dance floor. I usually have this on a wireless dimmer so I can make minor adjustments as necessary. There is a successful wedding videographer on the East Coast who makes this standard operating procedure for key events on the dance floor and claims no complaints. I have to say that, in my experience, judicial use of this same technique has yet to send any complaints directly to me.

which will produce a better quality: increased gain at shooting or Levels in post?

depends on your camera, depends on your NLE

ive never had an issue using a light at weddings.. some drunks might get pissed at me, but i dont care.. theyre not the ones paying me

Personally, I always try to make my original footage the best it can be. That way I will have more flexibility in post. The old "garbage-in garbage out" concept.

However, whatever you shoot onsite has to be based upon what you intend to do with it in post.

Waldemar,
I agree with you. Perfect image starts with good lighting. But in those occasions or scenes (COPS come to mind), which method will produce less of a mess? I've had to deal with a video shot on my gl2 at high gain, and i tried to reduce the ugly grain with Neat Video. It is a costly procedure in terms of perceived sharpness. I guess i need to experiment and see, which method will yield worse results.