With a full Spectrum converted camera, your sensor is open to the entire light range from UV to Infrared passing by visible light. You can even install a filter on your lens that only allows visible light to pass through, giving you the ability to capture images like a standard non converted camera. On a full spectrum camera the filter you choose is placed on the lens. The viewfinder and the sensor see the same filtered light at the same time. Therefore focus remains identical in liveview as through the viewfinder.