Creating Digital Snow

No need to worry if you snow's on your wish list this Christmas. If the weather turns out too mild or you're at work when the falls come you can turn on the snow in your photographs digitally later. Peter Bargh, editor of ePHOTOzine shows you how.

Snow, and rain are easy to create on any photo providing you have a basic understanding of your image editing program. In this tutorial, using Photoshop, I'll show you how to make snow.

1 Choose a photograph that will look natural with a snow fall. Ideally it should be one with at least a small covering of snow already. This shot, taken out in Derbyshire, is ideal. There's a small covering of snow and a blizzard is just what it needs to add to the wintery feel. I've resized it to 1600x1200 so that most digital camera owners can follow the tutorial using the same settings. Those with cameras that produce larger files can increase the values I select to get similar results.

2 Create a new layer Layer>New>Layer (Shift + Ctrl + L) I called mine, appropriately, snow and, Using the Rectangular Marquee tool, draw a box about 1/4 the size of the main image over the image. You should have now have a dotted line making a rectangular box in the middle of your photo.

3 Go to Edit>Fill (Shift + F5) and from the dialogue box that pops up select black from the "Contents - Use" drop down menu and click ok. This fills the rectangular selection with black and you will see the small layer thumbnail now has a black square in the top "snow" layer.

4 To create the snow go to Filter>Noise>Add Noise and from the dialogue box that appears set the Distribution to Gaussian and tick Monochromatic. This will give a random spread of white pixels which we will soon blur. The only other thing to control is the size of snow flakes and that's done by dragging the Amount slider left or right. A percentage between 40 and 100 will give anything from a fine particles of snow to a heavy downfall. I set around 60% which is a good balance, but try experimenting with different settings. At this stage you could also try the Threshold tip I've included at the bottom of the page.

Noise at 40%	Noise at 60%	Noise at 100%

5 Now go to Edit>Transform>Scale and drag the corners of the box so that it fills the whole image area. You should now have a black canvas with white dots of noise all over. This "digital snow" is now appearing as larger flakes and spread more over the picture so it looks less like noise. 6 Set the snow Layer blend mode to Screen so that the black disappears and the image below can be seen again. Now it's starting to look like a winter blizzard. And you could leave it like this. It will look more natural with a touch of movement though.

7 With the snow layer still active go to Filter>Blur>Motion Blur and from the dialogue box that appears set the angle in the direction you want the snow to fall. I am going to make it look like there's a breeze from the left so I need the snow to fall at a slight angle from top left down to bottom right. I've set -78. Adjust the Distance slider so it creates the motion blur. I've set 14 which stretches each snow drop in the direction of the angle set previously.

The higher you set the distance slider the longer the drop extends and the more unnatural it looks. If you make sure the Preview box is ticked you can see the real effect on your photo and can adjust both the angle and distance until they suit your photograph.

8 And that's all there is to it. If you prefer the snow to look less prominent you could adjust the opacity of the snow layer. As with all layered images, you can save the layers if you save the file as a Tiff or PSD file and come back and edit them again at a later stage. If you are sure you won't make any more changes flatten the layers to reduce the file size.

Tip - Using Threshold to change the density of snow

There's one other thing you could do to change the type of snow. We've already covered the Noise option to change the size of snow flakes but using Image>Adjustments>Threshold allows you to control the density of snow fall. Use this method after you've applied the Noise filter in step 4. Threshold turns everything black or white and the slider controls how much is black and how much is white. Drag to the left to increase white and to the right to reduce it. I dragged it a touch to the right to create a less thick snow fall.

Set threshold to around 150 for more snow	Set threshold to around 60 for less snow

Using the Threshold option can make the snow look even more realistic.