02 March 2009

Blue snow blues

My niece Simla took this picture of her dog Chester in Ottawa about a month ago when they had an unusual case of blue snow. Or, maybe they didn't.

ChesterInSnow1

When it comes to taking pictures in the snow, the exposure meters of cameras have never been reliable. This is not a problem specific to digital cameras; film cameras had the same issues. The snow is just too bright and it reflects the UV portion of sun light. To get the correct exposure you need to set the camera manually to overexpose.

The blue snow can be corrected in Photoshop. One way of doing it is with the color balance controls: increase yellow to decrease blue and increase red to decrease cyan until the snow becomes white. Usually, it is also necessary to lighten up the picture. Another way, which is faster, is to use the white dropper in the Levels dialog box. Click it on the snow and Chester will be cured of his winter blues instantaneously.

ChesterInSnow2

3 comments:

Anonymous said...

Or with a film camera using daylight film, one could use a UV filter or a Skylight 1A filter.

CHarlie

John said...

My digital camera has a "Snow" setting among its special scenes. That usually does the job pretty well, though I usually end up playing with the white balance anyway.

Anonymous said...

Your niece correctly exposed this picture; there is nothing wrong with the exposure. There is detail in both the snow and the dog's fur. This is hard to do, congratulations to her.

The blue color is due to the reflection of the blue light. As someone else wrote, a UV or warming filter would have taken car of this.

However, the collar and the fur have heavy cyan cast. Is she sure the white balance was set correctly? You might want to check the EXIF data on the original frame.