Adding condensation to a window, a glass or any other object is a simple, but delicate process. It involves creating the small droplets and then brightening and blurring them. Even an experienced graphic artist may require some trial and error to get it to look right on each photo. To follow this tutorial, use an image of any glass filled with a beverage.
Create a Background Copy by dragging the Background layer onto the New Layer icon at the bottom of the Layers panel.
Select the Rectangle Tool in the Toolbox. Using the Options bar, change the Fill Color and Stroke Color both to black. Drag the cursor over the image so that it covers the object. The rectangle appears as a new layer in the Layers panel.
Click the Filters menu, select Filter Gallery and then click the Grain thumbnail in the Texture folder. Adjust the Intensity and Contrast until you get a series of thin lines on the black background. Click OK.
Open the Filter Gallery again. This time, click the Craquelure thumbnail in the Texture folder. Adjust the Crack Spacing, Depth and Brightness to break up the vertical lines so they resemble streaky water residue on black glass. Click OK.
Select Blur from the Filter menu and click Gaussian Blur. Adjust the Radius to about 2 Pixels and click OK.
Click the Filter menu one more time, select Blur and then click Motion Blur. Change the Angle to anywhere between 85 and 95 degrees with a Distance of 4 Pixels.
Reshape the rectangle to fit the contours of the glass by using the Liquify Filter from the Filter menu, or by selecting Warp under the Edit menu's Transform option. If you're using Warp, reduce the Rectangle's Opacity in the Layers panel so you can see the object below it.
Click the Select menu and then click Color Range. Click on any black area in the rectangle and then reduce the Fuzziness to about 10 so you select only the black pixels. Click OK.
Make the Rectangle layer invisible in the Layers panel by clicking its Eye icon. Select the Background Copy layer.
Select Gaussian Blur from the Filter menu's Blur options and set a blur Radius of between 2 and 3 Pixels.
Click the Image menu, select Adjustments and click Levels. Change the right Input Level from 255 to 246. Click OK.
Select Deselect from the Select menu to see how your condensation looks. Use the Eraser Tool in the Toolbox to delete condensation from the background or areas on the glass that shouldn't be there. In our example, we've removed condensation from the base of the glass and from the foam upward.