Spotlight #2 - Infrared photography: introduction - Jason Mann

Infrared photography: introduction

14 August 2015

About the Spotlight series

In the Spotlight series I drill down into specific techniques of photography to provide insight on how to compose, shoot and edit photos using this technique.

In this post, the first of a three-parter about infrared photography, we'll look at the principles behind shooting in infrared and what equipment you will need. The next post will look at how to compose and shoot infrared photos. We'll then wrap up with how you edit and process your photos after shooting.


A brief introduction to infrared photography

Infrared photography is an innovative, technically-demanding method which can produce some stunning images. It has a steep learning curve, but I guarantee it will produce some beautiful shots and give you a whole new way to view the world.

Shooting in infrared is unlike any other type of photography. As a start, you can't even see your subject! It tends to work best with landscape shots due to the long exposures involved, and anything fast moving is generally out.

This is one type of photography that you won't be able to do with a compact camera or your phone. You need a digital SLR camera here, as you'll be needing custom filters and full manual control over your camera.

Once you've got your photo, processing it is also quite complex, and requires that you have some specialist software. I use Adobe Lightroom and GIMP.

With all that said, these spotlight posts will guide you through the whole process step-by-step. My aim is to give you enough knowledge to allow you to start experimenting on your own.

So let's get started with the principles of infrared photography.

Summer Snow


Knowing your subject

The properties of light

As with anything in photography, knowing your medium and your subject is key to getting a good photo. Unlike visible light photography, shooting in infrared has a few quirks that can catch you out if you're not ready for them.

Before you jump into equipment and composition, you should first look at infrared light and how it differs to visible light. This will allow you to avoid making key mistakes which can compromise your infrared photos. Don't worry, this won't be a deep dive into advanced physics, but enough of an explanation to give you an insight into how infrared is different. 

So what is light? Light is an electromagnetic wave with a wavelength which falls within the visible range of the electromagnetic spectrum. Let's break that down into manageable chunks and understand what it means.

The electromagnetic spectrum is a fancy way of saying that a certain type of energy in the universe, called electromagnetic radiation, behaves like a wave and has a range (or spectrum) of wavelengths.

Wavelength is the physical distance between the high points and low points of a wave. Think of waves in the ocean - they rise up to high points (peaks) and down to low points (troughs). If you placed a ruler between two peaks, the distance between them would be the wavelength. In ocean waves this might be a couple of metres. In the electromagnetic spectrum, the distances are much smaller, and are measured in nanometers (nm), or billionths of a metre, but the principle is exactly the same. 

Wavelength diagram

The range of wavelengths in the electromagnetic spectrum is huge. At one end you have Gamma rays and X-rays with tiny wavelengths of fractions of a nanometre. At the other you have radio waves, which can have wavelengths of several metres. Light is simply a specific range of wavelengths in this spectrum that our eyes can perceive, called the visible spectrum.

The visible spectrum covers electromagnetic radiation with wavelengths between 380 and 750nm. The specific wavelength of a bit of light is what defines the colours we see - shorter wavelength light between 380-495nm is blue or violet. Longer wavelengths of 620-750nm are red.

The properties of infrared light

With an understanding of what light is, let's look at what infrared light is and how it differs from visible light.

Infrared light is electromagnetic radiation with a wavelength between 700nm and 1,000,000nm (1mm). In many ways, it's very similar to visible light, except it just so happens to mostly fall outside of the range wavelengths of light our eyes can see.

I say mostly, because the starting wavelength of infrared, or 'near-infrared' light, of 700nm falls just within the range of the visible spectrum. We can actually see the very beginnings of infrared light, although most of it is invisible to us.

Infrared light has a few key properties which differ from visible light, so let's move on to working with infrared.

Electromagnetic spectrum

Image of the electromagnetic spectrum, highlighting visible light. Image from Wikipedia (https://commons.wikimedia.org/wiki/File:EM_spectrum.svg)



Working with infrared is different

Infrared photography is not what you're used to. Many of the rules you've learnt in photography have to be bent or broken. To get started, there are three key differences you need to know about: the focusing point, the brightness, and how objects appear in infrared.

Use a narrow aperture

Your camera's autofocus is set up to focus on objects which reflect visible light. Even with manual focus, you judge what's in focus using visible light through the viewfinder. Unfortunately, the focussing point of infrared light is slightly different to that of visible light (due to the difference in wavelength). That means a photo which was perfectly sharp in visible light will be slightly out of focus in infrared.

The best way around this is to use a wide depth of field (a narrow aperture, or high f-stop number) when shooting in infrared. This means that your subject should be nice and sharp in your final photo. It does mean you can't really do the shallow depth of field that works so well in portraits, but as we're about to see, portraits aren't on the menu anyway!

Infrared light is really dim

Compared to the amount of visible light around, infrared is really thin on the ground. That means that you're going to need long exposures and high ISO values. Really long. So far, I've been typically using exposures anywhere between 10 seconds and 3 minutes, with ISO values between 100 and 10,000. Bring a tripod, and a book, and don't try to capture anything moving.

Things look different in infrared

This is the really tricky bit. In infrared, the world is a totally different place. The amount of infrared light reflected by an object is different to the amount of visible light, which really changes how the world looks!

Leaves, grass and other foliage reflects infrared really well, meaning they will glow brightly. Branches, the sky and water do not reflect much infrared, so they will appear dark. Fabrics and clothes can have wildly different infrared appearances to visible light.

My advice here is be prepared to experiment. Take lots of photos. You won't really know what your photo is going to look like until you take it! I really like this aspect of working in infrared, because it encourages you to look again at the world.

As an example, the two pictures below illustrate how the same scene looks in visible light (left) and infrared (right). What looks boring in visible light looks beautiful in infrared.

Visible light & infrared comparison

Preparing your equipment for infrared

Check your camera can capture infrared!

First things first, you need to check that your camera can capture infrared light - not all can.

Most cameras have a filter in front of the image sensor specifically designed to block out infrared light, as it causes distortions to visible light photography. Despite this, most cameras can still sense some infrared.

There's no hard and fast rule to which cameras will work best. The only way to be sure is to test your camera yourself.

The remote control method

The easiest way to check how sensitive your camera is to infrared is the remote control test. This only works for cameras with live view modes - where you see the image on the digital display on the camera rather than through the viewfinder.

Set your camera to live view mode. Take your TV remote control and point it directly at the camera. Press and hold a button on the remote. If you can see a light red colour coming from the remote, you're in luck - your camera can sense infrared light.

The brighter the light, the better your camera can see infrared light and the shorter exposures you'll need. The photos below show the view through my 70D with a remote off (left) and with a button pressed (right). Notice the glow from the remote in the right picture - that's infrared light. 

The remote control test

Long exposure method

If your camera doesn't have a live view function, you'll have to perform a similar test using a long exposure. Set a long exposure with a low ISO on a tripod. Hold a button down on the remote while the shutter is open. If you can spot the light shown above, you're in luck.

Make sure to test your camera inside. Outside, the ambient light will make it harder to see the light from your remote.

Buy an infrared filter

Infrared light is much dimmer than visible light. To capture an infrared shot, you need to use a filter which blocks all light except infrared.

There are a few brands you can pick, but Hoya is extremely well-regarded in the industry. Cheaper brands may not actually block the right wavelengths of light they claim. If you can afford it, go for a well-known brand.

Filters come in different sizes. Each of your lenses will list the size of filter that it fits, normally shown on the front end in mm. On the photo on the right, my lens has a 58mm diameter for a filter.

My advice is to buy the largest screw-in filter you can afford, or the largest any of your lenses uses (they get expensive!) and then buy a set of stepping rings. Stepping rings allow you to fit one filter to all of your lenses by bridging the gaps. I got these on Amazon for £10.

As if that wasn't complicated enough, there are several types of infrared filter, designed to block different wavelengths of light. I advise you buy a 720nm filter, often known simply as R72. This is the most versatile and affordable filter.

I use a 62mm Hoya R72 filter, which cost about £25 on Amazon.

Filter sizes

Permanent modification - another option

You can opt to have your camera professionally modified to see infrared light. This is done by removing the filter on the front of the image sensor. I won't give it more than a passing mention here as it's very expensive and permanently limits that camera to infrared photography. Only do this if you're a pro doing large amounts of infrared work, in which case you're unlikely to be reading this!

Get a tripod

A tripod is essential, as you'll be taking photos with exposures in the tens of seconds.

I won't go into the merits of every tripod here, but if you're wondering what to get, I can highly recommend my recent purchase: the Vanguard Alta Pro 263.

It's sturdy and well-built, has a good range of height options, a decent ball-head and quick-release plate. Best of all, it has the awesome tilting central column which makes it great for macro photos and top-down views. I paid about £120 for mine a few months ago.


You're ready to shoot!

If you've followed me so far, well done! This has been an in-depth look at the principles of infrared photography and I've thrown a lot at you in a short space.

You now have an understanding of what infrared is and how it differs from visible light. You've tested your camera to ensure it can capture infrared, and you've got an infrared filter and tripod ready.

In the next post on infrared, we'll look at how to set up your camera and actually take your first infrared photo!

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