Revision: 20070721_081231 | All Revisions
Have you ever wonder what infrared does for night vision? Why does night vision goggles always use the infrared spectrum? After all, like visible light, infrared is just another part of the electromagnetic wave spectrum. It means that in order to even see infrared, something has to emit it and have it bounce off a surface. To answer that question, this article will show some practical examples.
The following are two photographs captured with the Sony DCR-HC90 camcorder in 3 MP photo mode, same focal length, same aperture, and same shutter speed.[[Image:DSC00318.JPG|center|thumb|400px|Night Vision. Visible light captured with Sony DCR-HC90. 5mm. f/1.8. 1/30 second.]] [[Image:DSC00319.JPG|center|thumb|400px|Night Vision. Infrared and visible light captured with Sony DCR-HC90. 5mm. f/1.8. 1/30 second.]]
Note that in the second photograph, where the infrared light is captured, the photograph is brighter, with more detail.
The reason is not that infrared light is brighter or more abundant at night than visible light. But rather, both infrared and visible light are captured in the second photograph. It simply means that the camcorder was gathering more light at the same aperture and shutter speed. This claim is validated in the next photograph.[[Image:DSC00320.JPG|center|thumb|400px|Night Vision. Infrared light captured with Sony DCR-HC90 and Hoya Infrared R72 filter. 5mm. f/1.8. 1/30 second.]]
You can see from this photograph that the infrared reflection is only slightly better than the visible light reflection. Although more detailed is gained around the driveway and the garage door, detail of the truck on the right is lost. This photograph is a huge step-down from the photograph that captured both infrared and visible light.