CCD Lens Info & Calculator
Most of viewing angle of a lens described by a vendor is a diagonal angle. But it's a horizontal angle that can represent a true coverage of an area. If you see a vendor selling a pinhole camera or a nanny camera at 90 degree angle, it's most likely to be a false statement because widest pinhole lens are 3.8mm (75 deg horizontal / 90 deg diagonal). But since 75 deg angle can cover most of the room, it's often goes unnoticed. We do however carry true 90 deg pinhole lenses L-2.9PSC at: http://www.spycameras.com/item8.htm . 

This calculator finds the lens size (focal length/mm) and the appropriate field of view, based on data entered for the CCD size, the distance from the camera to the target area, and the width of the target area to be imaged. Enter the numeric value for the distance from the camera to the target area and enter the numeric value for the width of the target area. All calculations take place at each entry. You may however, click 'Calculate' to update if needed.