Either you have a broadband camera like Andrea B. and you decide yourself where you want to cut off light.
Or you do like I did and put in a filter that cuts off at 600nm.
However, if you cut off light in a broadband body, you will see the image in your viewfinder when cut off at 600nm, but if you decide to go the 720nm route or higher, you will be shooting "blind".
Another drawback with broadband is that you will always fiddle with filters, either gels (back slots of lenses) or screw in filters. Then you won't be able to use very lens that you have unless you buy filters with all thread sizes of your lenses.
The drawback of the 600nm is that it is not 100% IR, since you will capture the visible range from 600-720nm (but who cares, right, as long as the photo turns out good)
