In reflected UV photography the subject is illuminated directly by UV emitting lamps (radiation sources) or by strong sunlight. A UV transmitting filter is placed on the lens, which allows ultraviolet light to pass and which absorbs or blocks all visible and infrared light. UV filters are made from special colored glass and may be coated or sandwiched with other filter glass to aid in blocking unwanted wavelengths. Examples of UV transmission filters are the Baader-U filter or the StraightEdgeU ultraviolet bandpass filter, both of which exclude most visible and infrared light. Older filters include the Kodak Wratten 18A, B+W 403, Hoya U-340 and Kenko U-360 most of which need to be used in conjunction with an additional infrared blocking filter. Typically such IR blocking, UV transmissive filters are made from Schott BG-38, BG-39 and BG-40 glass. Filters for use with digital camera sensors must not have any "infrared leak" (transmission in the infrared spectrum); the sensor will pick up reflected infrared radiation as well as ultraviolet, which may obscure the details that would be resolved by ultraviolet alone.