Last week, a dusting of snow showed me exactly where the cluster in my top-bar hive had gathered. Dead center on the uninsulated gabled roof were two circles of meltwater, so I knew the cluster was right below it. “Aha!” I said. “When my Flir One thermal imager arrives, I will test it on the top-bar hive.”
Sure enough, my very first thermal image showed the cluster centered top-to-bottom and left-to-right. There is something reassuring about viewing it, all snug and glowy, in the middle of winter.
Heat converted to visual images
So here are a few observations on my first attempts at thermal imaging. My husband helped me with this post by providing the comments in the gray boxes. He said the information comes from a Wikipedia article on thermography, the specifications of the Flir One, and his vast knowledge of engineering.
Thermal imagers work by converting heat into electronic signals which can then be recorded and viewed on a video monitor. The Flir One imagers designed to work with smart phones have two lenses, one to take a normal digital photograph of the scene, and one to sense heat gradients. In the final photo, the heat gradient is overlaid on the photograph so you can see where the heat is coming from.
Thermal imagers do not “see” inside the hive, but rather they detect heat coming from the hive. For example, the two photos shown here were taken of the same hive, one from the front and one from the back. From the front, the cluster is clearly visible, but from the back it is not. This tells me that the cluster is very close to the front of the hive because the wood in the front is warm.
Since the thermal imager detects heat, it does not show the cluster from the back of the hive because the wood back there is not nearly as warm. From the bees’ point of view, it makes sense that this cluster is in the front of the hive because that is the side facing the sun. The bees take advantage of existing heat whenever they can.
Rich says: In a nutshell, what the beekeeper sees is the heating of the wooden hive caused by radiant and convective heat transfer from the cluster to the walls of the hive. In turn, the emissivity of the wood is detected by the camera and converted to visible light, allowing the beekeeper to inspect the hive non-invasively.
A single image, taken from one side of the hive can reveal a source of heat, which is good evidence that there is a colony present in the hive. This single image obviously reveals the height of the colony. This alone is useful because a colony that is very high in the hive may be out of food and need supplementary feed.
An image from two adjacent sides, or even three or four sides, will help triangulate the location of the colony in longitude and latitude. The colony not appearing on one or more of the sides is likely to indicate the colony is distal from the image side, or that a draft within the hive is cooling the inner surface on that side. It is very unlikely that this result is indicative of a camera failure.
Features included in the Flir One
These little cameras are loaded with features. You can choose different color palettes to view the photos either before or after you take the picture. Different palettes show the heat gradients in different ways. You can easily take the photos and then scroll through the pallets to find the one that tells you the most.
You can also read the temperature in degrees C or F, or turn that feature off so you don’t see it in the photo. With a single swipe of the screen, you can remove the thermal image overlay and see the plain digital photo underneath which is helpful to better see where things are.
Thermal images around the house
As soon as Rich saw the thermal images, he (mis)appropriated my phone to take photos of windows, doors, and roof penetrations looking for heat leaks. Plus he discovered that the dog’s nose is really warm, white hot actually. Just saying.
The Flir One is useful for finding thermal leaks on houses. This is not a frequent use, but repairing these leaks, which can occur when water is entering too, saves energy, improves comfort for occupants, and prevents damage from becoming even more costly to repair as the problem lingers undetected.
The range of temperatures for thermographic images is -50°C to over 2000°C. The Flir One IR cameras operate in a much narrower range, with a “scene” temperature of 32°F to 212°F, perfect for beekeepers checking hives and homeowners looking for thermal leaks at their home. The Flir One may not be a good choice for a technician analyzing the performance of a boiler producing super-heated steam because its range of performance is too low. Infrared film is sensitive in the range of 250°C to 500°C, also of little use to beekeepers.
Worth the price if you can save some bees
Although I was hesitant to plop down money for the imager, I believe it may have already saved two hives. All my hives have candy boards in place, and I had no intention of checking on them further until the first of the year. But much to my amazement, the images show that two of my colonies have already moved up into the candy boards. I knew they were short of food going into fall, but this was unexpected. Time to buy more sugar.
I was first convinced of the value of these cameras when I saw the images taken by Maine beekeeper, Judith Stanton. She saw a mouse nest in her hive and was able to take it out before it did serious damage. Awesome. The take-home message here is important: if you see something weird in your photo, don’t blame the camera. Instead, open that hive the first chance you get.
Open your hive, share your finds
I’m in the process of setting up a gallery of hive thermal images. If you want to include your photos, you can email them to me (firstname.lastname@example.org). Be sure to say where in the world you are.
Honey Bee Suite
Flir One for iOS and Android are available on Amazon.
Note: This post contains affiliate links.