HD Webcast Video Production: Choosing a Video Camera

Video Noise

The physics of larger sensors can mean a cleaner or less noisy image. Video noise is very noticeable in high-gain or high-ISO situations but, similar to how audio recordings have a "noise floor" of undesired audio, video cameras have a "video noise floor" that is visible even before you increase the gain on a video camera. Some video cameras are noisier than others before gain is added. It's important to evaluate a video camera both with no gain and typical amounts of gain added to determine if it's suitable for webcasting, because some cameras might have a higher initial noise floor but are less affected at higher gain.

From my own experiences, I have observed that, in general, the smaller the sensor, the more noise will be present and CCD sensors have a lower initial noise floor than CMOS sensors. Newer video cameras also tend to have less noise overall and at higher gain settings than do older models. This is a rather general statement, and there will obviously be some exceptions, so it's best to test for yourself on specific models with live footage and not playback after codeccompression.

Reducing video noise is a factor of lowering the gain as much as possible and sometimes this might mean breaking the 180 degree shutter rule that stipulates that to eliminate intraframe blurring you want to record with a shutter speed that is twice that of your frame rate. In a 1080 30p recording, this means using a shutter speed of 60, but if your subject is a speaker at a lectern, you may prefer a bit of intraframe blur over a higher gain/video noise floor. Reducing the shutter to 30 lets in twice the amount of light.

Video Outputs

This series is about webcasting workflows, so I would be remiss if I didn't discuss the video outputs on video cameras in the context of webcasting. In a single-camera webcasting workflow, your primary consideration is that your webcast encoder offers at least one video input that matches the output of your video camera.

For multi-camera webcasting you need to use an HD video switcher and consider both the inputs and outputs of that device as part of the workflow. I'll discuss HD video switchers more in detail in the next article in this series.

Analog component video cables are one video output option, but in order to carry a non-digital HD signal, three cables are required. As a result, you won't find too many video switchers with component video inputs as they take up a lot more room on the video switcher. HDMI and HD-SDI are the other two options. Both carry the same quality of digital HD video signal but their differences have important workflow considerations.

HDMI cable is a consumer grade cable and doesn't lock like the bayonet on an HD-SDI cable (also known as a BNC cable) does. You can get long lengths of HDMI cable but not as easily as you can with HD-SDI cable, and you also can't run HDMI for as long a distance as HD-SDI. As it pertains to the video camera part of the connection, most video cameras have only one type of connection and a single output.

If your camera operator wants to use an external monitor to help with exposure and focus, then this requires you to split the signal in two. Unfortunately, when you use an HDMI splitter to connect both a camera operator reference monitor and a video mixer and one of the signals is interrupted, you momentarily lose the other signal. This happens more frequently than you might imagine; every time you change a battery on either the camera or the monitor or the tape on some video cameras, the signal to the video switcher gets interrupted.

For this reason, I prefer video camera with HD-SDI or multiple outputs. HD-SDI splitters don't interconnect each input and output the same way that HD-SDI does, so it's much more stable.

In the next article I'll review the Sony FS100 large-sensor video camera in the context of webcasting before moving to HD video switchers in part 3 of this series.