Understanding IR Filtration in a Digital World.

rainbowThe first step in unraveling the great mystery of what IR filters do, why you need one, and which one do you chose, has to start with an explanation of What IR is.  Infrared light is a part of the electromagnetic spectrum just bellow what we call visible light. Visible light is a very narrow part of the electromagnetic spectrum that the human eye is sensitive to and allows us to see. This is measured in wavelength between 390-700 nm (nanometers).  Essentially the longer the wave the warmer the light. Reds being in the bottom of that range and blues and violets at the top and a shorter wavelength. Infrared is actually split into three ranges described by their distance from the visible range. Continue reading

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IR + ND with Epic and Alexa

The question came up recently regarding a Red Epic camera and IR Filters.  Here’s the background. Digital cameras are very sensitive to light, and the infrared spectrum can cause your blacks to look red, also known as IR Contamination. The sensor cover glass in the camera is calibrated to remove Inferred light to give you the best colour rendition.  ND filters will block light, but not in the infrared spectrum, so the more light you block with ND filters, the higher the ratio is of IR light. Over a certain level, the built in filtration is not enough. Arri recommends the use of IR Filtration at and above ND.9.  I haven’t yet seen any specific recommendations from Red so I think it calls for a test. Continue reading