FOCUS STACKING: Focus stacking is a technique where you create a deep depth of field by combining multiple images with different focal points. This technique is useful for landscapes, macro, or product photography, among other things. Place your subjects (e.g. bottles or candles) equidistant from one another, in a row moving away from your camera. Use a 24-70mm or similar lens set to 32mm or 33mm (to simulate a 50mm lens on crop camera) or 50mm on a full frame body. Set aperture to f/4.0. ISO depends upon your ambient lighting conditions. Make sure the camera is securely mounted to a tripod and your ambient light is consistent.
At f/4.0 you will see that there is a large area out of focus. We need to shoot four separate shots, each at the same exposure, but each one focused on the center point of the subject. Here is one of the few times LiveView comes in handy. Use it to make a real close, sharp focus on each subject. Autofocus first, then manually fine tune with LiveView.
FOCUS STACKING II: Bring all four images into Photoshop. Create a new file matching the dimensions and resolution of the images just taken. Drag each image to the new file in reverse order. (the last shot is first, the first shot is last in the stack.
Select all the layers in layers palette and go to Image, Auto-Align Layers. From the window, select Auto and click OK. Once finished, go to Image, Auto-Blend Layers and from the window select Stack Images. Click OK. You may need to crop the final image to remove any softness or irregularities created by the focal differential.