How did the snowflake shadows happen?

[danwiz]

I took this photo and then when I looked at it later on the computer I was shocked and surprised to see that the snowflakes have shadows. There is absolutely no post-processing on this photo except for the addition of the frame. I really wonder how this shadow effect happened. Yes, I used the flash, but I have used the flash in snow scenes many times in the past and never achieved this effect. I only took the one shot, I wish I had noticed the effect right away and then I would have tried for more like this. But --- would I have been able to get the effect again or was it just a once in a thousand happening?

[D70FAN]

Reflection on double pane glass? It looks like the shadows come from flakes actually on the glass. It definately is interesting.

[danwiz]

Sorry, but no, not taken through any glass - I was standing outdoors.

[TheWengler]

Here's what I think happened...

When you use a flash you essentially have two exposures, one with ambient light and one with the flash. In the final photo they're layered on top of each other. If you have movement in your frame, this becomes more apparent. The flash occurs fast enough to freeze the snow in place. The shutter speed isn't fast enough to freeze the snow flakes however. So as the snow flakes continue to move there is enough ambient light for their blurred motion to show in the final photo as well. The streaks all appear below the snow flakes because your camera is using first curtain flash, which fires the flash off as the shutter opens. This means that the freezing action takes place at the beginning of the exposure. If you set it to rear curtain, the streak would appear above the snow flake. Hopefully that makes some sense. I'm not sure what level you're at in terms of understanding exposure so forgive me if I gave too much or too little information.

[danwiz]

I am at a high enough level of photography so that I completely understand what you are saying Lukas, and I believe that this answer makes complete sense. Great explanation! Do you think that I might have been able to achieve the same effect if I had taken another 10 exposures while standing there, or was it a "once in a lifetime" thing?

[TheWengler]

You could do it again as long as you have enough ambient light and the correct shutter speed.

[D70FAN]

Good explaination Lucas, but can't remember seeing this affect before. Repeating the image may be problematic as there are a lot of factors that may be hard to duplicate... but fun to try.

Domo, danwiz-san. That's a pretty fair amout of snow for Tokyo.

[danwiz]

Yes D70FAN, it was the biggest one day snowfall since 2006!

[Phill D]

Yes very well worked out Lukas. It was puzzling me how the light was set to get the shadow angles, they just didn't look quite right. It's now obvious from your explanation that the angles just depend on the trajectory of the snowflakes - simples! you are a genius.

[TheWengler]

you are a genius.

I try to tell my wife that all the time, but she's not having any of it!