New answers tagged snow
As you say, normally the flakes would be nearly invisible, however, the photographer has used a bright flash to illuminate the flakes, so that they are much brighter than the surrounding environment. This means that, even though they are out of focus, the flakes still appear in the image, but as big dots.
Ensure that steam exists(I'm not confident with that being the case here) Add contrast to the background as you aren't going to see white steam on a white background Add depth to the steam with something other than flat lighting(i.e. add a directed harsh flash)
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