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What is infrared Photography

Wednesday, July 6, 2011


What is infrared Photography

Visible light electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm. In  physics, the term light  is  refers to electromagnetic radiation of any wavelength, whether visible or not. In here, is what we will reveal with our gear. We seek for something that unvisible in our eyes. So we need a camera that able to capture the ultraviolet, visible light, and infrared illumination.
The light we ordinarily see by ranges in wavelength from about 400 nanometers (violet) to 700 nanometers (deep red). This narrow band, also known as the visible spectrum, enables you to see violet, blue, green, yellow, orange, and red colors, and all their combinations. But actually  the incoming light also contains a significant amount of invisible, nearinfrared (NIR) illumination, which is considered to be light in the 700–1200 nanometer range. Digital cameras can record light in this range when they have an IR filter in place. A typical light source could also contain light from the short wavelength end of the spectrum, the ultraviolet range, but the glass used in camera lenses does a pretty good job of filtering out most UV light.

Our biggest light source,the sun emits visible light, IR light and UV  light. But light from other sources ,Almost all light emits IR light. Candles or incandescent bulbs or even strobe flash for example also emits IR light. .In other words, you can creatively photograph IR light  not only on bright sunny day but also at night.

How we see an IR
You can see and record invisible light by using digital camera with  an IR filter attached in front of the lens (available at camera stores) . The fact is no need to do camera  modification if you just want to see an infrared, but the problem is the shake images and the need to use tripod because of long exposure.  This procedure made infrared photography so difficult. See my article do we need to convert our digital camera or not.  Alternatively, you can modify your digital camera by removing the hot mirror located over the camera sensor, and replacing it with a filter that allows IR light to pass through to the camera sensor, or put an infrared filter in front of the lens of camera with hot mirror removed and replaced by clear filter. This method will give you a freedom of taking infrared images just like a common camera.

Actually a digital camera imaging sensor is responsive to wavelengths from about 350nm to 1000nm. It makes the camera also can record ultraviolet light in the near UV range, and with a special filter, light in the near IR range. To prevent the camera capture the invisible color that make images not just like what we see, all digital camera manufacturers place a hot mirror inside the camera. The hot mirror reflects most IR and UV light, serving as a filter, and transmits only visible color like what we see with our eyes, to reach the camera sensor.

Using an IR filter on or inside the camera allows IR light to reach the camera sensor but blocks
most visible and UV light. The camera can now record IR light and you will see a new world that you never see before. Be creative photographer. Hey wait, what about the full spectrum camera???.  See my article for full spectrum camera

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