>There are some folks >who have the antialiasing/IR filter replaced (or, sometimes, >just removed) to allow more IR light to reach the sensor. As >far as I know, this makes the camera useless for normal >photography.
Just a small note on conversions.
There is two ways, full spectrum and IR. With IR the IR blocking filter on the sensor is replaced with a visible light blocking filter. That allows you to use the camera for IR photography as you normally would. But makes it useless as a regular camera.
Then there's full spectrum conversion where the IR filter is replaced with a clear filter. That allows you to use an IR blocking filter on the lens for normal photography and a visible light blocking filter on the lens for IR photography.
The significant difference is with the IR conversion you can use the viewfinder to frame the images as you normally use the camera while the full spectrum conversion you will need to frame the scene first and then screw on the filter, or use live view with the filter on already if your camera has live view.