This article comes from WeChat public account: SME Technology Story (ID: SMELab) , author: Bob Vishneshi / Sumukh Rao, translator: SME Technology stories from the topic map: vision China
From the perspective of photography art, Infrared Photography provides an opportunity to explore a new world—an invisible new world. Why is it said to be “invisible”? Because infrared light is outside the visible spectrum of the human eye, no one can “see” it directly with the naked eye unless certain equipment is used.
When photographers use infrared film or cameras to take photos, they will see an amazing new world. Colors, textures, leaves and plants, human skin and many objects in daily life can reflect infrared rays in a unique and interesting way, presenting a magical scene that cannot be imitated with tools such as Photoshop.
Infrared photography: Barbosville Vineyard Source: Photographylift
The first attempt at infrared photography began in the early 20th century . During the First World War, infrared photography proved to be very military value. BecauseIn order to use infrared spectroscopy images are less affected by atmospheric smog, and infrared images can also show a clear distinction between vegetation and buildings, which is more conducive to identifying potential enemy targets, such as camouflaged ammunition factories or forts.
From the 1930s to the 1940s, Hollywood filmmakers and amateur photographers began to notice the artistic application of infrared photography . At the same time, the military expanded its use of infrared camera technology during World War II. By the 1960s, infrared photography in the field of popular culture was almost a household name, and album covers for various pioneer music were happy to use this trendy element.
With the advent of digital cameras in the late 1990s, both conventional photography and infrared photography have undergone tremendous changes. In peacetime, the military use of infrared photography has appeared more in some criminal investigations, looking for forensic evidence that cannot be recognized by normal vision.
In terms of fine art photography, infrared photography not only presents a very surreal dramatic color effect when shooting landscapes, but also a very useful tool for wedding or portrait photographers. The reflected infrared light can not only make the vegetation appear icy white, but also make the skin appear milky white with a smooth texture.
As shown in the portrait photography below, infrared light has the effect of “smoothing the skin”.
Image source: Photographylift
From the photo above, we can also find a more amazing phenomenon: in fact, the model in the photo is wearing a black sunglasses, but due to infrared light can easily pass through the lens Therefore, the model eyes that are not visible to the naked eye are also revealed under the conditions of infrared photography.
This is a problem that has frequently caused controversy and vigilance during the popularization of infrared photography: Can infrared photography see through the subject?
To understand the “perspective” details of infrared photography, we must start with the nature of light. Light is a form of radiation that appears at different wavelengths and frequencies. Visible light, infrared, ultraviolet and X-ray are some examples of light forms. As the name suggests, visible light is the form of light visible to the naked eye.
Wavelength of various light
On the other hand, Infrared ( IR) , UV < / strong> (UV) and X-rays are invisible to the naked eye because they are in different spectrums that the human eye cannot perceive. If we want to see these lights, we need a A special sensor that is sensitive to the corresponding wavelength of these lights. For example, the sensor in the X-ray machine can capture light with a wavelength range of 0.01nm to 10nm, so it can “see” the human body through X-rays.
Similarly, infrared cameras, which began in the early 20th century, also have a sensor that can capture infrared light. In modern times, smartphone cameras are also sensitive enough that they all have the ability to capture infrared light. We can verify by a simple test: point the camera at the infrared transmitter of the TV remote control and press the button on the remote control, you will see the infrared LED glow on the camera’s viewfinder.
However, the sensitivity of mobile phone cameras to infrared light absorbed by objects is not high enough.
The location where the TV remote control sends infrared signals is generally made of plastic materials that are transparent to infrared light
Source: Andrew Martonik / Android Central
We all know that humans can see objects because they are absorbed and reflected by visible light shining on the objects . Suppose such a scene, we are in a dark room, the only light source is a flashlight. Hitting a beam of light, penetrating a piece of tulle and shining on a sphere, at this time we saw the tulle and the ball at the same time.
This is because the light shines on the tulle and penetrates it to shine on the sphere, and we receive both visible light at the same time. So the key to “seeing” is lightWhere did you go and what light can the “sensor” see .
X-ray light can penetrate human skin and muscles because their structure is not so dense. However, X-rays will eventually “shine” on high-density human bones, as long as we have the right sensors, we can “see” this picture.
The principle of infrared “see-through” is the same. It can penetrate the thin plastic outside like sunglasses and remote control shells, but not through the metal interior. It can also penetrate some loosely structured fabrics (especially vigilant is the clothing materials of swimsuits) , but it cannot penetrate most of our daily Clothing worn.
In the 1940s, American cinema audiences photographed with infrared film. Note the dark-colored glasses that were “see through” Source: TimeLine
Regarding the negative impact of infrared photography , controversy and discussion have occurred as early as the end of the last century.
In 1998, Sony released a camera equipped with night vision infrared technology, which was originally intended to facilitate night-time video shooting. But it was soon discovered that if infrared lenses are used in daylight, thinner clothes such as swimsuits will be seen through . The degree of transparency depends on the degree of absorption of infrared light waves by the fabric (also can be understood as the penetration of infrared light waves) .
In the end, Sony can only try to recall all 700,000 cameras that have been produced or sold, and made technical adjustments to the subsequent machines-as long as the aperture of the camera is turned on, this function will be forced to the maximum , So when this function is turned on during the day, only fully exposed waste film can be captured.
A unique art work that reasonably uses infrared photography
Compared with Sony ’s dilemma due to the frequent infrared photography function, another camera giant did the opposite.
The camera X-T1 IR launched by Fuji in 2015, the main function is that this camera can capture the light that human eyes can’t see. This is certainly not a camera specifically designed for perverts, it is a powerful tool for professionals.
Fuji said that X-T1 IR is suitable for crime scene investigators, healthcare applications and scientists . In the forensic world, infrared photography can be used to analyze blood stains, detect deep tissue damage and view scratches or unclear locations on documents.
Fuji X-T1 Series Camera
From the development history of infrared photography, we can really feel the saying “ The development of science and technology is a double-edged sword “. In the hands of the right users, they are beautiful tools for artistic creation, and they are the artifacts to reveal the truth; but in the hands of mischievous people, this technology may also become a weapon for hurting people.
In today’s more and more advanced technology, one hand for one handThe camera can also achieve such a powerful function of infrared photography. However, to spread a hidden technology to everyone, manufacturers must also consider comprehensively, learn the lessons of their predecessors, and make the most appropriate technical treatment.
Original link:
https://photographylife.com/introduction-to-infrared-photography
https://techpp.com/2020/05/13/color-filter-camera-see-through-objects/
This article comes from the WeChat public account: SME technology story (ID: SMELab ), author: Bob Vishneshi / Sumukh Rao, translator: SME Technology story