Infrared perspective filter

Homemade is no problem, provided that IR glass can be bought, but it can be bought in general large equipment stores. Self-control is of little significance ~

Infrared cut-off filter

If you use a film camera, you can buy a special infrared film (Ilford SFX200 is a common model), and then install an infrared filter in front of the lens (filtering out visible light and letting only infrared light pass).

Using numbers, I found an article:

Brief introduction of digital infrared photography

In fact, the basic principle of infrared photography, like general photography, is to use light to shine on objects and reflect them through the lens to form images in the camera. The only difference is between visible light and infrared light. Sunlight contains rich and varied light, and of course it also contains infrared light. When sunlight is reflected from an object to our eyes and cameras, we have actually received infrared light, but our optic nerve does not feel it.

Principle of digital infrared photography

In fact, the camera also receives infrared light, but the general negative film can't sense it. Traditional infrared photography relies on the negative film dedicated to infrared light, while the CCD or CMOS used in digital cameras can sense infrared light, but in general, the infrared effect cannot be seen because the amount of visible light is much larger than infrared light (another reason is that many DCs are equipped with IR cut filters).

The function of infrared filter is to block visible light and let infrared light pass through smoothly, except infrared cut-off filter, which is used to block infrared light. After the infrared filter is installed in front of the lens, the negative or CCD can only see infrared light, which is the simple principle of infrared photography.

Advantages of digital infrared photography

Compared with traditional infrared photography, the advantages of digital infrared photography are that traditional infrared film is expensive, and it is troublesome to keep (it needs refrigeration) and needs to be developed in a specific place. Digital camera can see the results on the spot, which is helpful to correct the parameters, and can meet the interactive application of general/infrared photography at the same time without two cameras!

Test your camera.

Generally speaking, the CCD of most digital cameras is sensitive to infrared light, but some manufacturers have added infrared cut-off filters in front of the CCD in cameras to block infrared light, which makes these cameras less sensitive to infrared light. There is a simple way to test whether the camera is suitable for infrared photography.

Hold the infrared remote control of general household appliances and press the button of the remote control for the camera lens. At the same time, see if you can see the bright spot from the LCD or EVF of the camera. If the spot of the infrared light on the remote control is clearly visible, that is good news. (The result of shooting the remote controller with Olympus C-2 100UZ, photographed by Steve Tang)

Buy infrared filters

The next step is to buy a suitable infrared filter.

The wavelength range of visible light is about 400nm-700nm, and the near-infrared light that CCD can induce is more than 700nm and less than 1200nm.

Hoya R72 or B+W 092 is just qualified at 720nm, but R72 can still let some visible light pass, which is a disadvantage. Better choices such as Tifeen 87 and B+W 093 are purer but more expensive.

speak from experience

After adding infrared filter, the luminosity is greatly reduced. My experience sets the exposure of Olympus C-2 100UZ to 100. Hoya R72 is generally used in sunny days. Even if the aperture is opened to the maximum (f2.8), the shutter is often 1/30 seconds or slower.

(This situation seems to indicate that C-2 100UZ also uses an IR cut filter, which blocks some infrared rays).

If the camera doesn't have hand shock prevention function, it often needs a tripod! At this time, the shortcomings of R72 become advantages, because a little visible light can make up the light.

The problem of inadequacy. With B+W 093 with opaque visible light, the situation of insufficient light is even more serious!

About visual angle

Infrared photography is often associated with perspective.

The so-called perspective is because infrared light can pass through some substances that are not very transparent to visible light. The premise is that there is enough infrared light, the outer layer can penetrate, and the infrared filter filters out all visible light interference.

For example, the best example is the dark protective film on the infrared remote control, with a filter in the sun to see how transparent it is.

This is the truth of some well-known 0 Lux NightShot Camcoder perspective photography.

But perspective photography not only needs a very high filter, but also has the effect of magnifying weak light, which is also one of the conditions.

Without the above brightening function, the perspective effect is very limited.

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Personally, infrared photography is like an alternative black-and-white photography, which is quite challenging in terms of light and composition and is a very interesting experience. The above is just my brother's idea for your reference. If there are any mistakes, please do not hesitate to correct them.