How much sensitivity do you usually use in sunny days, cloudy days, indoors and at night?

1.ISO, the lower the better, I don't need to explain this. 2. As for how high ISO can be opened in cloudy days and indoors, it is up to the machine. Some good machines can be turned on to 1600 or even higher image quality. Some machines should kneel down when turned on to 400+, and don't turn on to 1600 or above. At present, I haven't found that ISO can boot to 1600 without mania, even D3X. 3. At night, please adjust the ISO directly to the lowest, then F8, pre-lift the reflector, set the tripod cable to release, and slowly expose. . . If you need a high-speed shutter to shoot moving objects at night, use a flash, and flash if you can. . . I think shooting night scenes depends on high sense. Basically, photography has not started yet ~ ~ ~ ~ ~