Quote:
Originally Posted by Alan Anderson
This isn't a camera. Being "in focus" is irrelevant. What an extra lens can provide here is a combination of directivity and light-collecting power. For this application, non-imaging optics are fine. It's the size of the lens that matters most, and the focal length is (to a point) unimportant.
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Being perfectly 'in focus' is not important, you are correct. But being out of focus will lessen the energy recieved by the sensor, and as such will make it less sensitive (requireing more light to trigger). In addition, adding a lens will shorten it's field of vision.