All of these visible light cameras (daylight cameras, NVG cameras and infrared illumination cameras) work by detecting reflected light energy. However, the amount of reflected light they receive isn't the only factor that determines whether you can see with these cameras: image contrast is also important.
If you're looking at something that has a lot of contrast compared to its surroundings, you'll have a better chance of seeing it with a visible light camera. Without good contrast, you won't be able to see clearly no matter how bright the sun is. White objects seen on dark backgrounds have a lot of contrast, however, darker objects will be difficult to see in dark environments with these cameras, which is poor contrast. At night, when the lack of visible light naturally reduces image contrast, the performance of visible light cameras decreases a lot.
Thermal imaging cameras do not have these disadvantages. First, they have nothing to do with reflected light energy, everything you see in everyday life has a heat signature. That's why you have a much better chance of seeing things at night with a thermal imager than with a visible light camera (or even a night vision camera).
In fact, many objects you might be looking for (such as people) create their own contrast because they generate their own heat. Thermal cameras can see them very well because they can not only take images from thermal energy, but also image thermal energy, and they take advantage of the tiny thermal differences between objects to take pictures. Night vision devices have the same drawbacks as daylight and low-light cameras: they need enough light and enough contrast to create a usable image. Thermal imagers, on the other hand, can see clearly day and night while creating their own contrast. Without a doubt, thermal cameras are the best option for 24-hour imaging.
