Selection
In order to come up with a nice selection of thermal cameras, we compared quite a few brands and models. Based on this and keeping in mind our goal to compose a nice representation of the middle segment (€ 1.000,- to € 3.000,-), we finally made a selection of 10 thermal imagers. We focus on the serious hobbyist to the professional user.
Our experience
In the past months we have tested 10 thermal imaging cameras in a more closed and a more open environment. As far as possible, we took both photos and videos and tested the different zoom positions and colour palettes. In doing so, we soon realised that we preferred the colour palettes 'White hot' and 'Black hot', as these show the contours of the animals in the most detail. Next, we looked at a number of distinguishing features, which we will discuss in more detail below.
Image quality
For many the decisive factor when selecting a thermal imaging camera is the image quality. This makes sense since it makes the identification of a species a lot easier. Looking at the images, you immediately see that the image resolution is generally relatively low. Thermal imaging cameras have to deal with large wavelengths (IR light), so each pixel is larger than in standard cameras. In general, the more expensive the thermal imaging camera, the better the heat sensor and therefore the image quality. This can be clearly seen in the figure below where the image quality of a number of models are compared (see figure 2). Especially the image quality of both Pulsar models is amazingly good! The Flir Scout TK on the other hand, is like forgetting to put in your lenses in the morning. With these blurry images, it is difficult to find out exactly what you are observing. Especially when the animal is at a greater distance. Having said that, the price difference with the Pulsar models is also huge.
Zoom function
It is important to realise that there is such a thing as optical zoom and digital zoom. Optical zoom means that there is an actual adjustment of the distance between the different lens parts (as you can see in binoculars when you turn the lens, or when you move the lens forward in a digital camera). The resolution remains the same, but the magnification increases. With digital zoom, you actually take a cutout of the original image and enlarge it to fill the entire frame. Thus, the resolution decreases (the pixels become larger) and the image becomes grainy. Most thermal imaging cameras do not have an adjustable optical zoom but a fixed optical magnification (e.g. 1.5x). This means that the lens is set in such a way that the image is optically already slightly zoomed in compared to what you see when you just look at the object of interest. In addition, most thermal imaging cameras have a (often limited) digital zoom function. This function is useful to get a larger view of an animal, but be aware that the image quality deteriorates rapidly the further you zoom in (see example above).
Field of view
In addition to image quality and zoom, there is also the field of view (FOV). The width of the field of view depends on the focal length. As the focal length increases, magnification and range increase, but the field of view becomes smaller at the same time. What is desirable strongly depends on what you want to use the thermal imaging camera for. In a more closed environment, where you have limited visibility and approach animals relatively closely, it is very nice to have a large field of view, such as the Guide TrackIR-25. This makes it easier to see animals, especially fast moving ones like bats. However, you do notice that the animals are less recognisable, especially when the distance increases. For a more open landscape, the preference would therefore go to a thermal imaging camera with a larger focal length and thus a smaller field of view, such as the Guide TrackIR-50 or the Pulsar Helion 2 XP50.
Colour palettes
The way the difference in heat is shown on the display is determined by the colour palettes. The available colour palettes differ per thermal camera. For example, the Pulsar and Flir models have about 8 different colour palettes, while the Guide Nano models only have 3 colour palettes. In general, however, every thermal imager has at least 3 to 4 universal colour palettes; 'white hot', 'black hot', 'red hot' and 'ironbow'. Each user views and interprets the colour palettes differently, so everyone has a personal preference. The simplicity of 'white hot' may not provide enough detail for some, while the shifting colours of 'ironbow' can create unnecessary distractions. Our personal preference goes out to 'white hot' and 'black hot', as we feel this shows the contours of the animals in the most detail and also reveals more structure of the immediate surroundings (vegetation for example).
Ease of use
Apart from the image, it is also very important how a thermal camera fits in the hand and how easy it is to operate. We quickly discovered that the Flir Scout TK and the two Guide Nano models are very compact and easy to operate, partly because of their limited options. These models are therefore very suitable for a beginner. However, the Nano models can only make recordings via the app on your phone, which is not very practical in the field. You will notice a lack of hands when you want to aim the thermal imaging camera with one hand and need to hold your phone with the other to check the image and start the video.
For more advanced use, the models mentioned above are really too limited. That said, too many options can also have a negative effect on the usage of the thermal camera. A good example are the Pulsar models and the more advanced Flir Scion OTM266. These models have countless possibilities, which is obviously very handy, but also causes some confusion. As a user, you need to be well informed about all the different options, in order to be able to make optimal use of the device. It is also questionable to what extent the many available options are of use to you as a user, since you generally prefer a number of fixed options. The Guide Track IR models score very well on ease of use and offer a nice middle ground in terms of options between the very advanced Pulsar models and the more limited Flir Scout TK and Guide Nano thermal cameras. They have a good grip and are easy to operate with one hand, partly because the control buttons are close together.
