This is a horrible horrible feature!
1. What it really does is it digitally stretches the image which makes it appear to zoom in. And this causes dramatic quality loss, at 900 digital zoom the picture would look better with your eyes closed!
2. When you zoom in that far the camera starts to become VERY shaky, and you don't want VERY shaky video as it will give people a headache if they have to watch it.
3. You don't need this feature on the camera because you can do it on the computer! all you have to do is resize the image to say 200 percent (from 100) and you have a digital zoom!
An alternative to digital zoom
What you should be looking for is a camera with "Optical Zoom" this way the parts in the camera lens move accordingly to give you a full quality zoom in the optical zoom range.
You can also purchase lens adaptors that you screw on the front of the camera such as fish eye or a 2x telephoto lens. If you want 20x optical zoom, but you can only find a camera with 10x optical zoom, stick a 2x telephoto lens on it! Its much better then using the digital zoom!
In conclusion TURN OFF the digital zoom! The camera I use doesn’t even have a digital zoom feature, which is a great feature! haha….
If you want to get a close up just move closer, and if you can’t get closer, then bad luck, even if you do zoom in its going to look like dog droppings (of course you can come to a compromise, digital zoom of about 20-30 can’t really be noticed by the untrained eye).