Using your mobile phone, you can see infrared radiation – a normally invisible part of the electromagnetic spectrum. Ken’s Tech Tips looks at some of the physics of electromagnetic waves and explains how you can see this invisible world – and you don’t need anything more than the mobile phone in your pocket.

What is infrared radiation?

Infrared is a form of electromagnetic radiation. Other forms of electromagnetic  radiation (EM radiation) include visible light, x-rays, microwaves (the EM waves that wi-fi networks use and also the waves that cook your food in microwave ovens) and radio waves. The difference between all these different forms of radiation are the wavelength of the EM wave. We can illustrate this electromagnetic spectrum (CC-licensed image from Wikipedia):

What is the difference between visible light and infrared?

Visible light and infrared are both forms of electromagnetic radiation but with different wavelengths. Visible light has a wavelength of between 400nm and 700nm (a nanometer is so small that we can fit 100,000,000 in just 1 meter). We can only “see” the EM radiation in this range. At 700nm and longer, we enter the realm of infrared radiation.

Why can mobile phone cameras “see” infrared?

golden waterfall
Creative Commons License photo: paul (dex) busy @ work

Most cameras are designed to capture an image of what people can see. Hence a good camera would only detect EM radiation in the visible light spectrum (between 400nm and 700nm).

Yet the charged couple devices used within cameras are typically manufactured to pick up EM radiation between 350nm and 1000nm. This means they are capable of detecting infrared light too (between 700nm and 1,000nm is infrared).

To improve image quality, camera manufacturers typically add films and filters to block out infrared light and ensure only visible light reaches the CCD. If the infrared radiation was recorded by the camera and appeared in our photos, the photos would not be an accurate representation of what we can see – i.e. what we want to photograph!

Mobile phone cameras tend to be produced a lot cheaper than proper digital cameras and hence the vast majority of mobile phone cameras have a much thinner film/filter to block out infrared light. The lack of infrared filter is one reason photographs taken on mobile phones don’t look as good as those taken on proper digital cameras but it also provides us with an opportunity to use our mobiles to “see” in infrared.

How can I harness this fact?

Simply point your mobile phone camera towards a infrared light source and you can begin to see this new invisible infrared world!

For example, stick your phone camera in front of a television remote control and start pressing some buttons: you’ll see a few flashes of light (your remote uses invisible IR radiation to communicate with your TV – you wouldn’t normally be able to see this radiation as our eyes are not sensitive to the infrared wavelengths used by the remote). If you’ve got a Nintendo Wii, point your phone camera at the sensor bar. You’ll notice the sensor bar emits invisible IR radiation (this is how the Wiimotes track your movement).

Unfortunately, you won’t see the world in true infrared. Your mobile phone camera is sensitive to visible light too – and fortunately (although unfortunately in our case) this always registers much brighter on the CCD and drowns out the infrared image. If you’re really serious about seeing the world in infrared, you can pick up an infrared filter from Amazon. These filters will block out visible light and hence allow you to get a better image of the invisible infrared world.

Your Comments 11 so far

We'd love to hear your thoughts and any questions you may have. So far, we've received 11 comments from readers. You can add your own comment here.

  • Miriam Akinyi said:

    Hi, i like the article but would wish to ask some questions
    there is an agricultural test that i want to do but do not want to use a portable spectrometer. i intend to use a phone camera but the test requires a wavelength of between 1500 and 2600nm.

    Are there phones that have incoporated spectrometer to boost the wavelength?
    how can i up the wavelength of my phone camera?

    • Hi Miriam,
      As far as I’m aware, smartphones-based cameras are unable to pick up this range of frequencies. It’s likely you’ll need some specialist equipment for this, particularly if you’d like to get accurate spectrometer results.

  • Hi Ken Great article. Can you please help me with a couple related questions?
    Generally, my goal is to try to perform useful spectroscopy without a spectrometer attachment.
    Instead, I am hoping to identify small spectral fingerprints in the standard data captured by smartphone cameras and then reconstruct that data into useful spectral identification. So my questions are:
    1. How can I find out what wavelengths are captured (and not filtered out) in the iphone 7 and android?
    2. Do RAW images (which I can now use thanks to IOS10) capture more wavelengths than processed JPEGs? Any idea which new wavelengths are captured?
    3. If some wavelengths are being filtered out , can I turn off that filtering (e.g. Iphone selfie facing cameras don’t seem to filter out near IR)
    4. Generally, is there any way to reconstruct useful spectral information/data from RGB values or spectral information found in a RAW image? Any guidance you could provide would be sooooooo appreciated.
    Thank you John

    • Hi John,
      Thanks for your comment and some very good questions! Unfortunately, I’m not really sure the answer to any of them, so very sorry about this! You might be best off asking this on a photography forum (alternatively, see if you can contact Sony Semiconductor who manufacture the camera sensor on the iPhone).

    • Article in 2010, still getting comments in 2017 lol. If you’re interested, I just found this, should point you in the right direction. This pdf describes exactly what you are talking about.

      Good luck contacting the manufacturers for specs, I don’t think they’re publicly available. Cell phone cameras are big business. All this data has to be measured post production. For profit companies are not in the business of giving away secrets. In the pdf, they used a spectrometer, likely very expensive (I can’t find a price), and compared it to final camera images. They used DSLR raw data to eliminate JPEG processing differences as well. This isolated the differences in each stage of photo processing. I’ve known for a long time, that just the way a JPEG is compressed makes a big difference in photo quality. And indeed, high end cell phone cameras are now rivaling DSLR after JPEG compression, as the pdf shows. Raw however is different. I just reread your comment, and realized that you said IOS 10 can now give raw images. I didn’t know that. Yes, it theoretically should have a larger spectrum. Or at least, more data throughout the spectrum that is detected. Raw is always better. Uncompressed > compressed. (Raw versus JPEG)

      I found this after searching for info on infrared detection by smartphone cameras. What you’re talking about sounds interesting. Good luck!

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