Running an analysis

Three steps: load your frames, choose an area and settings, then Compute. Everything else is detail on those three.

Wizard steps: load frames, settings, optional sweep, then compute — **Figure.** Single mode goes straight to Compute. Sweep adds a setup step for ranges.

Step 1 — Load frames

In the app: tap each dropzone and pick images.

Photos is the system picker. Files is the only path to RAW and DNG (and to picking a video — see Getting started).

Step 1 with reference frame and three numbered deformed frames — **Figure.** Number badges on deformed frames are the analysis order. Use Sort before you continue.

Why it matters: the number badge on each deformed frame is its order, and that order is used everywhere afterward — frame 1 here is frame 1 in every result and export.

Getting the order right

Tap the sort icon to reorder. There is no way back to the picker's original order once you sort, so set it before you Compute. (With a single deformed frame the control is hidden.)

Sort	Use when
Name · A–Z / Z–A	Filenames carry the sequence
Date · oldest / newest	Filenames don't — uses capture time, then EXIF
Manual	Neither works — drag the thumbnails into order

Step 2 — Settings

Region of interest — defaults to the full image. Edit opens the ROI editor.
Single or Sweep — Single solves every frame once. Sweep solves one frame across many parameter combinations.
Advanced parameters — subset, step, strain window, kernel. If you copied a combination from a sweep lattice, a Paste params chip appears beside Reset and fills all three in one tap (the screen scrolls them into view).

Then tap Compute.

While it runs

Points solved and convergence update live.

Cancel stops at once — nothing is kept. Keep the app open; there is no resume if the system stops the app while it works.

A short run is not a failed run. If two frames in a row fall below 50% convergence the images have decorrelated and semper stops rather than grind on. The frames it solved before that point are real data — they are saved as a shorter analysis, and its Home row records why it stopped. A 50-frame test that stopped at frame 40 still gives you frames 1–39.

If it fails outright: see Troubleshooting · during a run for the exact messages and what each means.

Parameters (single mode)

The two you actually tune: subset (how big a patch each point matches) and strain window (how much the strain is smoothed). The defaults are sensible — the app even recommends a subset from your image.

Diagram of subset window size versus step spacing on a grid — **Figure.** Subset is the match window. Step is how far apart grid points are.

Parameter	Range	Default / reset
Subset size	15–121, odd	Recommended from your image
Step size	1–30	5
Strain window	5–101, odd	15
Kernel	4×4 Bicubic / 6×6 Keys	4×4 Bicubic

Virtual strain gauge related to strain window and step — **Figure.** Quote VSG with strain results: VSG = (strain window − 1) × step + 1, in pixels.

Full table with when-to-raise / when-to-lower: Parameters.

Region of interest

Draw a box over the part of the image you want measured; erase holes over anything that would spoil the match, like grips or markers.

ROI editor with crop rectangle on a speckle image — **Figure.** Crop sets the area to correlate. Erase punches out grips or markers that would decorrelate.

Draw — pick Rect or Square and drag on the image; drag inside to move, corners to resize, with size and position shown live. Manual — type X, Y, W and H exactly and Apply. Crop sets the area to correlate; Erase punches holes in it.

If it fails: an ROI smaller than the subset will not run — enlarge the ROI or shrink the subset.