What is infrared photography? A beginner’s guide


The photography is a bit trippy. When we take a photo, we are essentially not capturing the world, but rather simply the proof that it exists.

When you use a camera that closely mimics the way we see, this obvious truth is one that can be easy to overlook. Infrared photography dispels this illusion by showing us things from a slightly different angle.

What is infrared light?

The electromagnetic spectrum

Amitchell125 / Wikimedia Commons

Visible light, as you probably already know, is only a very small segment of the spectrum of electromagnetic radiation. At one end of this visible corner is a high energy blue light. At the other end of the spectrum is red light, characterized by much longer and slower wavelengths of activity.

Infrared light is slower than even the slowest red light visible to us. This makes it totally imperceptible to us visually, but that doesn’t make it any less important.

How does infrared photography work?

An example of an infrared photo of a landscape

The way conventional photography works is very similar to our own visual mechanism. How, then, can a normal camera “see” something that we cannot?

Basically, human vision and camera vision are indeed very similar. Camera sensors are, however, much more mechanically sensitive. They are able to “perceive” infrared light as an extension of the visible spectrum, albeit among the much stronger visible light that accompanies it.

In order to produce an image characterized exclusively by infrared light, all a camera needs is a filter that blocks all other wavelengths of light in the visible spectrum, as well as the ultraviolet light above.

What is an infrared filter?

Optical filters come in many forms, some more convenient than others. Many filtration manufacturers produce an IR cut filter. These types of filters actually block infrared light from passing through the sensor. Filters like this should not be confused with a clean and simple IR filter which actually does the opposite.

Like many types of camera filters, infrared camera filters allow light to enter selectively by wavelength. Tiffen is the industry standard for infrared filters, but there are plenty of more reasonable options available as well.

What is infrared photography for?

Distant objects in space emit or reflect light that reaches us over time. When light travels, it expends energy. The farther away the light is from the source, the slower each photon will travel along each ray.

If an object in deep space is far enough away from us, this effect essentially makes it “too dark” to be seen by ordinary means. The originally visible light it delivers can already travel too slowly to be seen the moment it hits us, falling below the low end of the visible spectrum and spreading into the near infrared region.

Infrared space photography is able to capture this type of light, which makes these celestial bodies much easier to study from home.

NASA infrared astrophotography

ESA / Hubble / Wikimedia Commons

Infrared photography also has some practical applications here on Earth. Some types of legal tender, for example, have interwoven “invisible” ink patterns that reflect infrared light. Counterfeit banknotes can be distinguished from real ones thanks to an infrared filter.

An infrared photo of a five dollar bill

In the world of forensics, IR photography can be used to see things that the human eye may not immediately notice. Blood stains can be difficult to pick up when splashed on a dark carpet. Because blood absorbs more infrared light than carpets or fabrics, infrared photos can help investigators see what is in front of them more clearly.

Related: What Does a Forensic Analyst Do?

How to take a photograph with an infrared lens

Two IR filters

Peter Halasz / Wikimedia Commons

To start taking infrared photos, all you need to do is invest in an infrared camera filter. But how does an infrared filter affect the photo taken? We’re glad you asked.

Infrared color spectrum

Photography with infrared lens radically changes the color palette from what we are used to seeing. The false color representation of invisible infrared light will give the impression that someone has adjusted the “tint” setting on the whole world.

The sky will appear in a nightmarish darkness. Portraits of people take on a strange quality, similar to that of an alien. The freckles disappear, the excess melanin indistinguishable from the rest of the skin.

The most noticeable difference between infrared images and normal photography, however, is the appearance of nature. The green color of plants and leaves will now appear as titanium white. While not particularly useful when shooting color photos, this effect will often create a black and white photo that is much more visually appealing when shooting in nature.

A comparison between infrared photos and the originals, both in color and in black and white.

Yottanesia / Wikimedia Commons

Infrared focus

Another consideration is concentration. Due to its longer wavelength, it converges to a point which will be different from that of visible light emanating from the same source.

Related: What Is Depth Of Field And How Does It Happen?

Any type of single lens reflex camera relies on mirrors to function. Mirrors reflect infrared light only in a thermal direction. This unfortunate fact makes these systems almost useless when shooting in infrared light; SLRs and DSLRs depend on the intrinsic properties of visible light in order to predict where incoming rays will meet.

The infrared index mark on a camera lens

Adjusting these tools to make them suitable for infrared photography essentially amounts to recalibrating them. Some lenses are printed with an infrared index mark, usually as a red dot slightly offset from the mark that usually indicates correct focus. Sticking to the correct rating for the type of photograph you are participating in will yield the appropriate results.

In order to focus on an object 50 feet away when taking a normal photo, you would roll the barrel until the 50 foot mark was aligned with this focus index indicator. by default. When shooting with infrared light, you would do the same, using only the red mark right next to it.

If you’re shooting with a mirrorless camera, you’re in luck. In the absence of mirrors separating the plane of the photograph of the subject, the focus is determined directly at the level of the sensor. No special measures should be taken to properly focus the image.

Infrared film photography

Another option is to use infrared film, just like the photographers that existed long before us.

Infrared film photography is a process that takes place throughout the life of photography. It requires a specific type of infrared film which cannot be processed and developed with the same type of chemicals as regular film. Even though the infrared film is sensitive to infrared light, an infrared filter will still be necessary for the most effective result possible.

Either way, for the most striking end result, you should shoot subjects that are generously illuminated by a powerful source, such as the sun. Smaller light sources can also work, but usually only if you’re shooting very close to them. Intensity is what you are looking for here. A weak or diffuse source turns into even weaker infrared light, which will be more difficult to photograph.

Infrared photos: something a little different

Infrared photography certainly has its own unique charm.

While not exactly the way to go if your goal is to paint a picture of the world as we know it, infrared images offer a glimpse of what looks like an alternate version of reality. For some, this can be a welcome and refreshing departure from the ordinary.

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