If we want to capture a small control cabinet containing 2 mm diameter wires on a thermal image - measuring only 45 x 30 cm in size - we need a 640x480 pixel thermal camera. With a 320x240 pixel camera, only a 22 x 15 cm area can be measured in a thermal image, and with a 160x120 pixel device, only an 11 x 7 cm postcard-sized area can be captured! (The calculation is based on the required geometric resolution, which is non-negotiable!)
Interpolation to 640x480 is not a substitute (where only "averaged" pixels are inserted between the measured pixels to improve the visual appearance of the thermal image; the required geometric resolution is not achieved, instead, 75% of "falsified" data is stored). Similarly, resolution-enhancing procedures based on 640x480 pixel hand tremor (e.g., Superresolution, Maxresolution) are not a substitute either, as they result in blurry thermal images with cameras slower than 50 Hz, or (to conceal their shortcomings) switch to interpolation (without warning).

In summary:
Calculate the required pixel resolution for capturing a single thermal image of the object to measure its details accurately! The detector pixel size always determines the true limit of measurement capability. (Exception: micro-scan capable thermal cameras with a price tag of several million forints.)

Note:
160x120 pixels (interpolated) actually represent only an 80x60 pixel detector
320x240 pixels (interpolated) actually represent an exact 160x120 pixel detector
320x240 pixels / Superresolution 640x480 actually represent only a 320x240 pixel detector

We only want to take thermal images by hand. So, with a handheld camera, no tripod - nothing special! Nothing special?
Let's just remember that before the era of mobile phone "photography," we knew the maximum allowable shutter speed for taking motion-free handheld (i.e., without a tripod) images of stationary objects: 1/60 second! This is therefore the maximum allowed integration time even for a handheld thermal camera! Translated to frame refresh rate, this would be 60 Hz. Since some time is needed for the thermal camera for mathematical operations and image creation based on the color scale, the integration time for a 50 Hz frame refresh rate thermal camera is around 1/60 second. Therefore, any handheld thermal camera with a frame refresh rate of 50 Hz or faster is suitable for capturing motion-free thermal images when held by hand. For slower devices, the use of a tripod or other stabilization is necessary!

In summary:
For handheld imaging, a thermal camera with a maximum 1/60 second integration time must be used. This is only guaranteed for thermal cameras with a frame refresh rate of 50 Hz or faster. When using slower thermal cameras handheld, expect blurry (and thus unusable) thermal images due to motion! When dealing with moving objects or being in a moving vehicle, thermal cameras slower than 50 Hz offer no chance of capturing motion-free images!

Note:
50 Hz frame refresh rate: minimum requirement for correct (motion-free) handheld imaging
33 Hz frame refresh rate: 66% chance of correct imaging (for stationary objects and steady-handed operators)
25 Hz frame refresh rate: 50% chance of correct imaging (for stationary objects and steady-handed operators)
15 Hz frame refresh rate: 30% chance of correct imaging (for stationary objects and steady-handed operators)
9 Hz frame refresh rate: only 18% chance of correct imaging (for stationary objects and steady-handed operators)

Firstly, we must decide whether we want to capture a nice colorful image (as if using night vision) or if our goal is contactless temperature measurement. For the former, feel free to use any device, possibly built into a phone or attachable to one, but these are generally unsuitable for temperature measurement. Why? Because they are non-radiometric, hence not calibrated, and the manufacturer does not dare to provide information on temperature resolution, measurement accuracy, or even measurement range. In these devices, you might be able to set an object emissivity, but you won't find other parameters required for measurement (e.g., ambient temperature, transmissivity) in the menu system, because they are not there! Therefore, they are not suitable for measurement - regardless of the manufacturer's product, the generation, or the hypermodern top model touted as professional!
For contactless temperature measurement, calibration is needed (not just at one point, but across the entire sensor surface), along with the definition of correct measurement capability. Industry-specific requirements vary, but obviously, a more accurate and higher-resolution device can handle even lower-level tasks much better. Moreover, a higher-capability thermal camera can be utilized more effectively. For instance, an 80 mK resolution thermal camera can only be used for assessing the thermal insulation of residential buildings if the temperature difference between indoor and outdoor remains at least 15-18°C consistently, whereas for a 30 mK resolution thermal camera, an 8-12°C difference is sufficient. Since there are usually many more days from late autumn to early spring where the daily peak temperature is well above 5°C than below it, the 30 mK thermal camera can be used on at least twice as many days as the 50 mK model.

In summary:
Only thermal cameras that are radiometric, calibrated, and equipped with appropriate thermal resolution and absolute measurement accuracy are suitable for temperature measurement. Everything else is just night vision!

Note the following professional examples:
For building thermography, a measurement range of -20°C (-40°C) to 120°C is required, with an accuracy of +/-1.5°C (or better) and preferably a thermal resolution of 50 mK (or better)
For electrical equipment measurements, a measurement range of -0°C (-10°C) to 200°C is needed, with an accuracy of +/-1.5°C (or better) and a thermal resolution of 80 mK (or better)
For biological measurements, a measurement range of -20°C to 120°C is necessary, with an accuracy of +/-1°C (or better) and a thermal resolution of 30 mK (or better)

Here we encounter the greatest misunderstandings. We have already discussed interpolation (as a pixel-doubling procedure). Its application is not recommended from a professional point of view because it results in 75% false data, while neither the measurement accuracy nor the thermal camera's geometric resolution increases. From a measurement technology perspective, procedures such as overlaying thermal and visual images (e.g., composite representation, fusion, overlay) and projecting visual image contrast lines onto the thermal image (e.g., MSX) are equally useless. None of these methods lead to more accurate temperature measurements; on the contrary, due to the appealing visuals, users may not even notice that the thermal image's resolution is insufficient or that the focus is poor! Lastly, procedures based on hand tremor for resolution enhancement (e.g., SuperResolution, UltraMax) can unequivocally be stated as almost useless because they result in blurred thermal images with thermal cameras operating at less than 50 Hz. Why? Because it requires 16 thermal images, from which 4 alignable images are selected. For example, with a 33 Hz thermal camera, the 16 thermal images require half a second for capture! By that time, the user's hand will definitely move more than the half-pixel required for the method. The image will either blur or - to cover up the deficiency - be interpolated. The only solution left is to use a sensor with a pixel count suitable for the measurement requirements or the micro-scan procedure. Unfortunately, the latter is only achievable with high-priced thermal cameras.

In summary:
Interpolation: does not increase geometric resolution, measurement accuracy, or pixel resolution; in fact, it generates 75% false data (more disadvantageous, therefore not recommended)
Composite representation, fusion, overlay: does not increase geometric or pixel resolution, nor measurement accuracy (solely for documentation purposes, not recommended for measurement use)
Projection of visual image contrast lines (e.g., MSX): does not increase geometric or pixel resolution, nor measurement accuracy (solely for documentation purposes, not recommended for measurement use)
Resolution enhancement based on hand tremor (e.g., SuperResolution, UltraMax, Dynamic Resolution Enhancement): results in blurred thermal images with thermal cameras operating at less than 50 Hz, hence practically unusable