The use of infrared photography

Before the birth of digital photography, special infrared film was needed to take infrared photos. The photosensitivity of film can be controlled by adjusting its chemical composition. Friends who engaged in black-and-white photography in the early days know that black-and-white film can be divided into dichroic film and panchromatic film. Dichroic film is only sensitive to light of a certain color, panchromatic film is sensitive to all visible light, and infrared film is particularly sensitive to infrared light in a specific wavelength range. Shooting and developing with infrared film is technically difficult and costly, and ordinary photographers rarely have the conditions to try it. It is mostly used in scientific research, criminal investigation, military and other fields. Because different substances have different absorption properties of visible light and infrared light, some differences that cannot be seen under visible light can be found through infrared photography. Infrared photography is often used in the inspection of criminal investigation technology to achieve the following purposes: to display ink, graphite pencils, carbon ink copy paper and ink handwriting covered or contaminated by aniline dyes, organic dyes and red stains; Identify the structure, stains and spots of textiles; Display vague postmark marks; Show faded or discolored handwriting or patterns; Shooting outdoor scenes shrouded in mist; Displays the handwriting of a document that has been dug or scraped.

For example, this local hat is what we saw with the naked eye when shooting with an ordinary digital camera.

However, the effect of infrared photos is very different, and the originally inconspicuous lines and pores are particularly prominent. This is because the absorption and reflection properties of sewing thread of pure cotton cloth and chemical fiber are very different. The cotton fabric will absorb infrared rays, while the sewing thread of chemical fiber will almost completely reflect infrared rays (the close-fitting clothes of pure cotton are very comfortable to wear because it absorbs the infrared rays of the body and then radiates them out, instead of reflecting them back to the human body like the chemical fiber fabric).

In addition to the above technical applications, infrared photography has a very unique expressive force in the field of artistic photography, especially in the field of landscape photography, and the imaging effect is quite special, which also makes many photographers obsessed with it, so that they have fans.

Asserting that "once you take the first infrared photo, you will be fascinated by this fantastic effect." You will be fascinated by it and cannot extricate yourself. "