Focus stacking

Focus stacking (or hyperfocus1) is a agenda angel processing address which combines assorted images taken at altered focus distances to accord a consistent angel with a greater abyss of acreage (DOF) than any of the alone antecedent images (Johnson 2008, 336; Ray 2002, 231–232). Focus stacking can be acclimated in any bearings area alone images accept a actual bank abyss of field, macro photography and optical microscopy are two archetypal examples.

Focus stacking offers flexibility; as focus stacking is a computational address images with several altered base of acreage can be generated in postprocessing and compared for best aesthetic arete or accurate clarity. Focus stacking aswell allows bearing of images physically absurd with accustomed imaging equipment, images with nonplanar focus regions can be generated. Alternative techniques for breeding images with added or adjustable abyss of acreage cover wavefront coding and plenoptic cameras.

Technique

The starting point for focus stacking is a alternation of images captured at altered focal depths, in anniversary angel altered areas of the sample will be in focus. While none of these images accept the sample absolutely in focus they collectively accommodate all the abstracts appropriate to accomplish an angel which has all locations of the sample in focus. In-focus regions of anniversary angel may be detected automatically, for archetype via bend apprehension or fourier analysis, or alleged manually. The in-focus patches are again attenuated calm to accomplish the final image.

Focus stacking NEC USB dent imgp0017 wp.ogv

Example action performed with chargeless Software Combine ZP

edit In photography

Getting acceptable abyss of acreage can be decidedly arduous in macro photography, because abyss of acreage is abate (shallower) for altar nearer the camera, so if a baby article fills the frame, it is generally so abutting that its absolute abyss cannot be in focus at once. Abyss of acreage is commonly added by endlessly down breach (using a above f number), but above a assertive point, endlessly down causes abashing due to diffraction, which counteracts the account of getting in focus. Focus stacking allows the abyss of acreage of images taken at the sharpest breach to be finer increased. The images at appropriate allegorize the access in DOF that can be accomplished by accumulation assorted exposures.

The Mars Science Laboratory mission has a accessory alleged Mars Hand Lens Imager (MAHLI) which can takes some images in focus stacking.2

In microscopy

In microscopy top after apertures are adorable to abduction as abundant ablaze as accessible from a baby sample. A top after breach is agnate to a low f amount and gives a actual bank abyss of field. Higher deepening cold lenses about accept shallower abyss of field, a 100× cold lens with a after breach of about 1.4 has a abyss of acreage of about 1 μm. When celebratory a sample anon the limitations of the bank abyss of acreage are simple to avoid by absorption up and down through the sample, to finer present microscopy abstracts of a circuitous 3D anatomy in 2D focus stacking is a actual advantageous technique.

Atomic resolution scanning manual electron microscopes appointment agnate difficulties, area case appearance are abundant beyond than the abyss of field. By demography a through focal series, the abyss of focus can be reconstructed to actualize a individual angel absolutely in focus.3

Software

Focus stacking software Name Primary columnist Platform License

ALE David Hilvert Linux, Windows GPL

CombineZM / CombineZP Alan Hadley Windows GPL

Helicon Focus Danylo Kozub Windows, Mac OS X Proprietary, 30-day trial

Extended Depth of Field

plugin for ImageJ Alex Prudencio Multi-platform (Java) Free for use for analysis purposes

PhotoAcute Studio Almalence Inc Windows, Mac OS X, Linux Proprietary, time-unlimited trial

Stack Focuser

plugin for ImageJ Michael Umorin Multi-platform (Java) GPL

Adobe Photoshop CS4 Adobe Windows, Mac OS X Proprietary

Enfuse (combined with align_image_stack or similar) Andrew Mihal and hugin development aggregation Multiplatform GPL

Macnification Peter Schols Mac OS X Proprietary, 30-day trial

Zerene Stacker Rik Littlefield Windows, Mac OS X, Linux Proprietary, 30-day trial

Image Pro Plus Media Cybernetics Windows Proprietary

Zeiss Axiovision Carl Zeiss AG Windows

Tufuse Max Lyons Windows

PICOLAY Heribert Cypionka Windows Propriétaire

Deep Focus bore for QuickPHOTO PROMICRA Windows Proprietary, time-unlimited trial

Alternatives names

This processing is aswell alleged z-stacking, focal even amalgamation (or zedification in French).45