What's the use of infrared filters?

The appearance of the infrared filter shows that the vitreous body is completely opaque and black. Because what we can see with the naked eye is only a small part of the whole electromagnetic spectrum, that is, the visible region, and actually there are rays that our retina can't perceive, such as ultraviolet rays and infrared rays. In the spectrum, the visible region of human eyes falls between 430 nm and 690 nm, and the wavelength of infrared light is longer than that of visible light. Different from ultraviolet light and visible light, the large wavelength of infrared light can easily penetrate any object, which means that infrared light will not be refracted when it passes through the object. The infrared filter makes use of this characteristic of infrared rays, allowing only long-wavelength infrared rays to pass through and filtering out short-wavelength ultraviolet rays and visible light.

The CCD photosensitive elements used in digital cameras and video cameras can sense infrared rays. In order to ensure that normal shooting will not produce color shift due to infrared interference, camera manufacturers install ICF (infrared cut-off filter) in front of CCD to block infrared rays and transmit visible light. Contrary to ICF, the function of infrared filter is to block visible light and let infrared light pass through. A camera with night shooting function is to remove this ICF through a mechanical device, so that the CCD can fully receive infrared rays.

Do actual shooting.

After installing the infrared lens, turn on the night shooting mode to shoot.

In the summer when the sun is strong and the infrared ray is sufficient, excellent infrared effect can be obtained. 950nm lens is suitable for outdoor shooting in strong sunlight, not suitable for indoor and ordinary intensity sunlight. Generally, 850nm infrared filters are commonly used. Limited by physical characteristics, this wavelength can still capture a large-span light environment from indoor to outdoor through a small amount of visible light. In addition to overexposure in a very strong sunlight environment, it is generally competent. You can use the medium gray mirror to reduce the light intensity and shoot.

To see the perspective effect, please refer to the following steps:

1: Take a piece of chemical fiber cloth.

2. Put a newspaper below.

3. The camera (video camera) plays infrared night shooting function.

4. aim at the subject and adjust the focal length until you see the text under the cloth.

You can refer to this method when shooting distant objects in the future.

Note: the night shooting mode must be turned on after the infrared lens is installed, and it must be turned off before the infrared lens is removed, otherwise the strong light may damage the CCD of the digital camera.

aftertreatment

The photos taken by infrared photography are only monotonous green, so it is easy to process them into a black-and-white photo with special effects. Just do a very simple process in Photoshop, use "Image → Adjustment → Auto Gradient" in the Photoshop menu, and then change the image mode to "Grayscale" ("Image → Mode → Grayscale").