zstacking

Z-stacking, also known as focus stacking, is a technique used to increase depth of field in digital imaging by capturing and combining multiple images taken at different focal planes along the optical axis. The goal is to produce a single image that is sharp from front to back, often with higher apparent resolution than a single shallow-focus frame.

In practice, a series of photos is collected with the focus gradually moving through the subject, typically using a motorized or manual focus drive on a microscope, macro rig, or camera setup. The spacing between focal planes depends on the subject, lens, and desired depth of field. After acquisition, alignment (registration) may be performed to correct any drift or misalignment between frames.

Processing involves selecting or blending in-focus regions from the stack. Common methods include focus measure-based selection, where the sharpest areas are merged, and multi-scale or pyramid fusion techniques that preserve detail and minimize artifacts. The result can be a single infinitely sharp image or a dataset suitable for 3D reconstruction or depth mapping.

Applications are widespread in light microscopy, histology, materials science, and macro photography of small subjects, where a shallow depth of field would otherwise obscure details. Z-stacking can also facilitate quantitative analyses and high-resolution imaging in research and education.

Challenges include alignment errors, uneven illumination, computational demands, and artifacts such as halos or ghosting if the stack is poorly acquired. Software tools used for z-stacking range from dedicated programs (for example, Helicon Focus or Zerene Stacker) to image editors and plugins that support focus stacking and stacking workflows.