Can I use my digital camera as a web cam? If so how?

Cannon SD 400 connected Via USB

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I'm pretty sure most digital cameras dont have that capability. The only thing I can think of is if you can record something if your camera has a video feature, and then you can send that file to the person. But I do not think you can do live feed like you are talking about. But like the person said above, I supposed it would depend on the make and model.