Solution:

When using a flash for shooting in snowy outdoors, or environments where there are many floating particles and fluffy dust in the air, white circles may appear in captured images.

The light emitted from the flash reflects on the dust and particles in the air that are in front of the subject, and that light gets captured by the camera, which results in white circles in images.

Particles floating in the air (dust, dirt, etc.)
Flash light that reflects on dust and dirt

To prevent this, it is best to capture images in environments with no floating particles, but if that is not possible, the following measures are effective.
- Brighten the surroundings so that a flash is not required.
- For models with the zoom function, shoot at the tele-end.
- For models that can be used with Speedlite flashes, use a Speedlite flash and distance the lens from the flash when shooting.