I'm lost again. Is backlight photography harmful to SLR or lens?

Whether in theory or in practice, the harm of backlight photography is small in probability.

Although the basic principle of lens is convex lens, there are two points to pay attention to. First of all, the lens is imaging, not focusing. Secondly, the aperture of the lens is limited, that is, the light source that can be gathered is much smaller than a magnifying glass.

When shooting strong light, the cmos sensor may be overloaded, but the result of overload is that nothing can be seen, or the color cast, because the cmos photocell does not rely on external light to generate electricity, but the power supply of the camera itself is electrified, and the light changes the resistance of the photodiode.

The problem faced by photographic equipment in strong sunlight is that the shell temperature is high, which causes some synthetic materials to crack and more expensive fluorite to be damaged.