The HV30 will automatically give you gain in a low light situation, if you don't know what gain is, its the camera amplifying your image to make it brighter, but you loose a lot of quality. Theres two ways to avoid gain on the HVs
1) Make sure your camera has a memory card in it. Pressing the photo button half way will show you the shutter speed and f-stop of the camera. Start lowering the exposure of the camera and checking the shutter and aperature. Once they start changing, you have eliminated gain. I know that sounds confusing, but its not that bad
2) Put the camera in spotlight mode or sunset mode, they both have no gain, sunset mode will oversaturate and give you a warm color temperature. Unfortunately, you dont have as much control over the camera in these modes