Sunday, January 15, 2017

Creating a real snow effect in Photoshop

There are several ways of creating an artificial snow effect in Photoshop. I have done a number of these and keep a supply of just snow images in what I call my "Utility Images" collection for whenever I need to quickly pop some snow into a shot. The thing that makes the scene below interesting is that the snow is not artificially created, Instead I used images from the actual falling snow scene I was photographing. When you think about it, achieving a shot like this in one go with a flash is really just a balanced exposure, in-camera double exposure of the flashed image over a regular image of a scene. This time around I decided to take the exposures separately and double-expose them in Photoshop.

Both images below were done using this technique. Once scene darker than the other because they were taken at different times as darkness was falling over the city.

 I had been attempting to capture this scene of snow falling over the city by using a flash to bring out the white snow flakes in the foreground.  I liked the way the accumulated snow on the water towers echoed the white circles of the falling snow. Problem was that the background scene was so low in contrast that the snow flakes over-powered it in most of my shots, and you couldn't see the subtlety of the snow-covered water towers on the roofs of the building. I kept trying to capture the scene with variations between the scene exposure and flash exposure, as well as trying different aperture settings to alter the size of the flakes. Working that way was a bit too serendipitous and I kept ending up with shots where the flakes were too large, too small, or in the wrong place.

I already knew how to add falling snow in Photoshop by creating a layer with a black background and the putting white dots of varying sizes and shading all over it. Once this layer was placed over a snow scene and its layer mode changed to "Screen", it gives a very realistic interpretation of falling snow. I am working on a new set of actions and overlays for MCP Actions, and had been creating a set of snow images to include so that adding snow to an image is as simple as drag-and-drop. 

The photo above of the city is what the scene looked like when photographed while the snow was falling. Although the snow was heavy, it did not record with a straight exposure of the scene until I added a flash. The idea occurred to me that perhaps I could split the exposure in two -- one of the scene and one of the falling snow -- and then combine them later in Photoshop by over-laying the snow on top of the actual scene. This would give me far better control over the size and positioning of the white flakes so that they no longer obliterated the scene below.

Here's how I did it:

The image of the city was a straight photograph with normal exposure taken with a Fuji X-Pro2. (My X-T2 is still in the shop as a result of my last snow photography catastrophe!) Next, I mounted a Nikon Flash on the same camera and began taking photos of just the snow. I knew from experience of making these combinations that I needed a black background for the white flakes. To achieve this I simply raised my shutter speed to 1/250 second. The scene was already dark and this speed rendered it black. With the flash on full power and the lens used mostly at wider apertures, I was able to obtain sufficient contrast between the snow and background. I experimented with different lenses, a short zoom set to f/4 or 5.6 for smaller flakes, and a 23mm or 35mm prime where I varied the aperture setting between f/1.4 and f/2.8 to achieve really large flakes.

For shots where the contrast was not quite sufficient I simply added some more in Photoshop with a Levels adjustment layer where I squeezed the left and right sliders together until it looked right. Changing the snow layer mode to "Screen" makes the black disappear leaving only the white snowflakes over the scene below.

The interesting thing about this technique is that it is really just a double exposure of the actual scene done in Photoshop instead of in camera, and, if you save a collection of these snowflake photos and vary the flake sizes by changing apertures, you will be able to add snow to any scene the same way. For the photo below I combined a couple snow shots of varying sized flakes to achieve the effect in a scene where there was no falling snow. One of the nice things about adding the snow this way is that you can easily eliminate distracting flakes by using a layer mask and painting them out of areas like the model's face.

I will be including a full set of varying snow sizes in the next set of overlays I am preparing for MCP Actions. 

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