Is the humidity in sauna days in Beijing harmful to SLR cameras?

The climate with increased humidity is very bad for SLR cameras and lenses. SLR can really work in many bad weather conditions, such as very cold or very hot temperatures, dustproof and waterproof dripping, and some high-end professional SLR can even splash water directly.

But that's only for short-term shooting needs, and it doesn't mean that the SLR can be invulnerable. For example, in hot and humid weather, water molecules are omnipresent in the air, and the lens is prone to mildew and coating damage when it is wet, while the mechanical components and electronic devices in the body and lens will be oxidized, rusted, short-circuited and damaged by moisture.

Your buddy's approach is correct. In this case, pulling the camera out for a walk will help to eliminate the water vapor inside the camera and keep the dryness inside the camera lens. However, it should be noted that this is not bask in the quilt, and you can't be poisoned in the sun for a long time.

The general way to store SLR equipment is to use silica gel desiccant and put it in a camera bag or drying box, which needs to be replaced regularly.

There is also a good way to use electronic moistureproof box. This moistureproof box needs to be plugged in, and the humidity in the box can be adjusted (47-52 in the north and 42-47 in the south). The electronic moistureproof box has stable humidity and low power consumption. At present, famous brands include collectors made in Taiwan Province, Wan Defu made in Guangdong and Huitong.