I need to get my neighbors drug dealing activity on video. I don’t know what kind of camera to buy. The subjects are about thirty feet away, and I want to be sure to get clear video. Can someone explain about wide angle lenses, what would get a better picture, 3mm or 6mm?
There is not enough detail to tell.
The focal length of a lens alone does not give any information as to what field of view it will have at 30ft. It is also necessary to know the sensor size to be able to tell. Or if the camera or lens specs have angle of view, that’s even better.
A different sensor size behind same focal length lens will produce different angles of view. The bigger sensor, the smaller angle.
If you know the angle, you can use the simple geometry to figure out the field of view of a camera.
This article may help explain what it is:
http://en.wikipedia.org/wiki/Field_of_view
Also this one:
http://en.wikipedia.org/wiki/Field_of_view
The only thing I can tell you, is that 6mm is going to be twice as close view as 3mm. So 3mm is a wider view, and 6mm will be more of a close-up (given both have same sensor size). But if you get too wide, you lose details, if you get too close, the action may happen outside of camera view, or faces get cut-off. That’s all I can tell from available information. Sorry couldn’t help you any further without the extra data.
LEM.