Standard digital SLR cameras are equipped with deep red cut-off filters which do not allow near infrared (IR) photos to be taken. To get around this, Hutech offers special dedicated IR versions of selected Canon digital cameras. These cameras feature sensor-mounted visible light blocking filters (cutoff at 720nm) with special anti-reflective (AR) coatings for the IR spectrum. In addition, the system is re-tuned for correct operation of the auto-focus (AF) function when adequate IR light is available. Photos are composed using the viewfinder in visible light. Manual focusing is also possible after determining the IR focus offset for the lens in use. The 40D features a live preview mode which is convenient for focusing and composition using the rear LCD screen.   Canon 5D and 40D Visible light blocking filter used in IR cameras.