Focus stacking (also known as focal plane merging, z-stacking or focus blending) is a digital image processing technique which combines multiple images taken at different focal distances to yield a greater depth of field (DOF) than any of the individual source images. Focus stacking can be used in any situation where individual images have an undesirably shallow depth of field; macro photography and optical microscopy are two typical examples.
There are a variety of focus stacking software to choose from. Adobe Photoshop also offers focus stacking.
Zerene-Stacker trial 30days download
Helicon focus trial 30days download
CombineZP free software download