Apple QuickTime Informações Técnicas descarregar pdf (Página 64)

64 Chapter 6 Setup Example

The Camera Is the First Link

Since the camera is the first link in the video signal chain, it is very important. Two main

things determine a DV camera’s picture quality:

• Lens quality. The better the lens, the better the image.

• Image capture mechanism. DV cameras use charge-coupled devices (CCDs) to

convert the picture into electronic signals. The number and size of the CCDs affect

the quality of the image.

Optical zoom gives better quality than digital zoom, but zooming should be avoided

or kept to a minimum when streaming a live presentation to avoid degrading the

stream.

Lower-end DV cameras use a single charge-coupled device (CCD) to capture the

complete image, whereas higher-quality cameras use three separate CCDs to scan

the red, blue, and green content of the image, giving a better quality scan. CCDs

range in size from 1/4 inch to 2/3 inch; bigger CCDs give better resolution.

Here are other desirable features:

• You should be able to override automatic camera settings.

• You’ll want to use a separate microphone that can plug in to the camera for optimal

sound pick-up. A built-in microphone is unsuitable for most situations.

• The camera should accept professional XLR plugs (as opposed to the 1/8-inch mini-

jack connectors). It should also have a headphone jack for monitoring the audio

input.

• Finally, a FireWire output enables digital transfers and automated capture, which can

save time later.

Keep the Microphone Close

The microphone is the first link in the audio signal chain and so is also very important.

Dynamic microphones are a good all-around choice and can be purchased for as little

as $100.

The best way to improve audio if the room has bad acoustics is to place the

microphone as close as possible to the person doing the speaking. Use a small lavalier

(lapel) microphone clipped to the front of the speaker’s clothing immediately under the

mouth, or use a handheld microphone.

In the case of a panel discussion, use multiple microphones, preferably on sturdy

stands, and a small audio mixer. Connect the mixed stereo output from the mixer into

the line input on the DV camera.

If using an external microphone or mixer, make sure that all the connectors are securely

plugged in to assure reliable audio. Plug a pair of headphones into the video camera’s

headphone output to make sure that you can hear the audio and that it’s not distorted.

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Apple QuickTime Informações Técnicas Página 64