Create realistic fog in your images using Photoshop.
1.) Open an image of your choice
2.) Click the New Adjustment Layer icon and select Hue/Saturation
3.) Apply the following settings
4.) Next, click the Add layer mask button
5.) Select the gradient tool and make sure black is the foreground color and white is the background
6.) Fill the image from bottom to top with gradient
7.) Select the Rectangle Marquee Tool and apply the following setting
8.) Make a selection somewhere near the center of the image
9.) Create a new layer above the background layer
10) Select Filter > Render > Clouds to fill the selection with clouds. Press Ctrl+D to deselect.
11.) Select Edit > Transform > Perspective. Drag the corner handles until you have something like this:
11.) Select Edit > Transform > Scale. Change the Width setting in the toolbar (W:) to 1000%
12.) Right click the layer thumbnail and select Blending Options.
In the dialog box, alt+click the black slider at the left
13.) The slider will split in half, slide to the right as below
Feel free to adjust the opacity or blend options to your liking.