focus-stack

focus-stack is a free desktop utility for turning a sequence of differently focused photographs into one image with greater depth of field. It is most compelling for microscope photographers and technically minded users who want control over alignment and processing rather than a cloud workflow. Its depth-map outputs and cross-platform binaries add flexibility, but substantial RAM requirements can determine whether it is practical for high-resolution stacks.

Overview

The software examines each pixel across the input frames and selects the sharpest source, producing an extended-depth-of-field composite. That method suits microscope work, where a specimen can extend beyond the shallow depth of field of a single exposure, and it also applies to other subjects photographed at successive focus settings.

Automatic alignment can resize and rotate stack images so their content lines up. You can skip alignment or adjust how it is handled when the frames are already registered or automatic correction is inappropriate. In addition to the finished stack, the program can create a depth map and a 3D preview derived from that map, giving advanced users intermediate data to inspect or reuse.

Key features

• Alignment controls: Resizing and rotation address small framing differences between shots. The option to bypass or modify alignment is valuable when a controlled camera setup needs no correction or when automatic movement would be undesirable.
• Processing controls: Denoising and consistency filtering help tune how the sharpest regions are selected, while batch size and thread count expose practical control over processing workload.
• Image compatibility: Inputs can use formats supported by OpenCV, including JPG, PNG and TIFF. The output format is chosen through the file extension, with JPG and PNG identified as output options.
• Depth products: A depth map and 3D preview are optional outputs rather than separate applications. They make the tool more useful for users analyzing focus variation, while casual users may only need the composite.
• Acceleration: OpenCV's OpenCL interface can use a compatible GPU when available. An option to disable GPU acceleration helps when that path is unsuitable on a particular system.
• Resource tuning: The README estimates roughly 100 MB of RAM per megapixel at default settings, or about 50 MB per megapixel with one thread and a batch size of two. Those figures make conservative settings important for large images or long stacks.

Pricing

focus-stack is free: the focus-stack plan costs nothing. There is no trial because the software is already available without charge, and no seat, usage quota or renewal limit is stated. The free model is a straightforward fit for personal, educational and experimental use, but buyers seeking vendor support or a packaged commercial service should look elsewhere.

Platforms

Desktop support covers Linux, macOS and Windows. Binary packages are listed for Windows 10, Ubuntu 20.04 and Mac OS X through the GitHub releases page; the releases page shows Version 1.5 and a separate prerelease named latest. Linux compilation requires OpenCV 3.0 or newer plus basic build tools, so Linux users outside the listed binary target may need to build it themselves. The macOS application is unsigned and may be quarantined by the operating system, adding a security prompt and extra setup friction. A third-party Android app uses focus-stack's algorithm, but that is not the desktop program itself.

Who it's for

Choose it for microscope photography or any desktop workflow involving focus brackets, especially when you need alignment controls, depth data or tunable CPU/GPU processing. It is a better fit for users comfortable with technical settings and memory planning than for photographers seeking a polished, guided editor. High-megapixel stacks deserve particular caution: the estimated per-megapixel RAM use can quickly exceed modest system memory, although single-thread and small-batch settings reduce the estimate at the cost of processing throughput.

Pros and cons

• Pro: Sharpest-pixel selection is purpose-built for extending depth of field from focus-bracketed images.
• Pro: Resizing, rotation, denoising, consistency filtering, batching and thread controls provide meaningful workflow tuning.
• Pro: Depth maps and 3D previews add analytical output beyond the final composite.
• Pro: Free distribution and an MIT license suit open-source, educational and budget-conscious projects.
• Con: The estimated 100 MB per megapixel default memory use can make large stacks demanding.
• Con: Unsigned macOS software may be quarantined, complicating installation.
• Con: Linux users may need OpenCV and build tools when a suitable binary is not available.

Alternatives

For a broader directory of options, see Focus Stacking Software.

• Focus Stacking Online is the better choice when you want free focus stacking across Android, iOS, desktop systems and the web rather than a desktop-only utility.
• CKAN is another free, MIT-licensed option for Linux, macOS and Windows.
• ImageFocus Alpha fits users with compatible Euromex camera models who need free software across mobile and desktop platforms.
• PlaneFuse suits readers wanting free personal or commercial use, no tiers and API, web or self-hosted deployment.
• ChimpStackr is a free, GPL-3.0 multi-platform focus-stacking alternative.
• ForgePix is free MIT-licensed software for Linux, macOS and Windows.
• OpenFocus offers a free MIT-licensed GUI on Windows and macOS with CLI support on Linux as well.
• Shine Stacker is a free download for Windows, Mac and Linux with an LGPL-3.0 license.

Verdict

focus-stack is a strong choice for microscope photographers and technically confident desktop users who want free, controllable focus stacking with optional depth outputs. Its main reason to choose it is the combination of alignment and processing controls at no cost. Look elsewhere if your machine cannot comfortably meet its memory demands, if you need a signed macOS installation, or if you prefer a cross-platform web or mobile workflow.