Stacking

Once you’ve selected frames in the filmstrip, pressing S (or clicking Stack selected images [S] →) hands them off to the stacker. This page explains what’s happening and what comes out the other side.

What focus stacking does

Macro depth of field is shallow — often a millimeter or less at high magnification. A single frame can only have a thin slice of the subject in focus. Focus stacking combines multiple frames shot at different focus distances into one image where every region is sharp.

Macro Studio’s stack happens in three phases:

Alignment — corrects for focus breathing (the magnification change between frames), camera movement, and rotation. Each frame is warped into the same coordinate space as the others. This runs automatically on every stack.
Sharpness analysis — for each pixel, the stacker measures which frame has the sharpest signal at that location.
Blending — the sharpest detail from every frame is combined into the final image.

One engine, nothing to configure

Earlier versions of Macro Studio asked you to choose a stacking method (Pyramid or Depth Map) and tune detail and depth sliders. That’s gone. Macro Studio now uses a single unified stacking engine that combines the strengths of those older approaches automatically — more detail, cleaner backgrounds, and fewer artifacts on difficult stacks, with nothing to pick or tune.

That means stacking is genuinely one click: select your frames and press Stack. The engine renders fine structures like antennae, hair, and bristles cleanly, keeps out-of-focus backgrounds smooth, and handles subjects whose parts cross over each other — without a method choice or a detail slider in sight.

GPU acceleration

Stacking is GPU-accelerated, and there’s nothing to switch on — Macro Studio detects your hardware and uses it automatically.

Any GPU works. Whether you have a discrete graphics card or an integrated GPU built into your processor (such as Apple Silicon), Macro Studio can hand work off to it.
The right work goes to the right place. We benchmark each step of the pipeline to know which computations are best handed to the GPU and which run faster on the CPU, then split the work accordingly.
Discrete GPUs are preferred automatically. On a system with both a discrete card and an integrated GPU, Macro Studio auto-detects them and picks the discrete one for the best performance.
No compatible GPU? No problem. Stacking falls back to the CPU automatically — you get the same image, it just takes a little longer.
There is an off switch, for troubleshooting. Preferences → Advanced → Disable GPU acceleration moves every part of stacking onto the CPU. It’s for answering “is the graphics driver to blame?” when a stack comes out corrupted — leave it off otherwise.

What stacking outputs

When you press Stack, the result appears in two places:

The history strip at the bottom of the Editor — every stack and edit lands here (up to 25 results; older ones drop off the front as new ones arrive).
The center canvas — your active result, ready for masking, adjustments, crop, spot correct, and Save.

Pressing Stack takes you to the Editor so you can watch it come together. If you’d rather keep your place in the filmstrip and carry on selecting the next bracket, turn on Stay in the Library after starting a stack in Preferences. The stack still runs and still lands in the history strip — and the EDITOR tab picks up a progress bar under its label, pulsing when your result is ready, so you can tell at a glance how it’s going without leaving the Library.

The result already has a Look baked into it — a Natural-to-Enhanced strength that controls how much contrast and punch is applied on top of the raw blend. New installs bake Enhanced at 60%; if you’ve been using Macro Studio for a while, yours stays at the original full Enhanced. You can change it per-result in the Editor or set the default for new stacks. See Look.

Your finished image isn’t written anywhere until you Save… — the result lives in Macro Studio’s in-memory project until then, so you can stack, edit, and pick the best version before committing to disk.

Stacking does need temporary scratch space on disk while it runs, though. Each frame is written to a scratch file as it’s processed, which is what lets Macro Studio stack more frames than would fit in memory at once. If the scratch volume can’t hold the stack, Macro Studio tells you before it starts rather than failing partway through — the message names the volume it measured and how much space to free. You can point scratch at a different drive under Scratch folder for stacking in Preferences, which is useful when your system drive is tight but you have a fast external with room.

The reduced-memory notice

On a machine that’s short on free RAM, an amber notice can appear during a stack:

Running in reduced-memory mode — stacking will be slower. Close other applications to free up about 6 GB and speed up stacking.

This is advisory, not an error — your stack is running and will finish normally, just more slowly, because Macro Studio has fallen back to a more memory-frugal path. It explains the case where a stack seems to be crawling while your CPU and GPU look barely busy. Closing other applications and re-running gets the faster path back. The notice clears itself after about 20 seconds, and you can dismiss it by clicking it.

If you already know why your machine is short on RAM — say you routinely run heavy disk or processor work alongside Macro Studio — the notice fires on nearly every stack and stops being news. Click Don’t show again on the notice itself, or turn off Show performance notices in Preferences. Preferences is also where you turn it back on. Stacking speed is unchanged either way, and the details still go to the debug log.

When a frame is hurting the stack

StackCheck looks at what each frame actually contributed and points out any that look like they dragged the result down (misaligned, oddly lit, or simply unused) with a button to stack again without them. It’s a beta and starts switched off; turn it on in Preferences → General.

Stacking a whole folder at once

Got a folder with several brackets mixed together? Autostack splits it into separate focus-bracket sets by capture time and stacks each one automatically. See Autostack.