Sessions: images, settings and saved work

Before anything else in PIVlab, you need images loaded. This page covers importing an image sequence, and — because it trips people up — the difference between a session (everything: images, masks, results) and settings (just your configuration, reusable on a different dataset).

Starting a new session

Choose File → New session (Ctrl+N), or click the first icon in Main tasks quick access. This opens the Input data panel shown here, with three ways to get images in: Import images (from disk), Load session (resume earlier work — see below), and Acquire images (capture directly from a connected camera).

PIVlab Input data panel with a loaded image list — The **Input data** panel, with four Kármán-vortex image pairs loaded.

Importing images

Click Import images to open the image-import dialog shown below. Browse to your folder (a Regular Expression Filter field narrows down large folders), select the files you want, and choose an image sequencing style — this tells PIVlab how to pair up your files into frames:

PIVlab image import dialog: sequencing style, folder browser, and the list of images selected for import — The image import dialog. Pick a sequencing style (left), select files and click Add to move them into the Images selected for import list, then Import.

Style	Pairing	Use it for
Time resolved	`[A+B], [B+C], [C+D], …`	A continuous recording where every image is reused as both the second half of one pair and the first half of the next — gives one vector field per consecutive frame step.
Pairwise	`[A+B], [C+D], [E+F], …`	Discrete double-frame/double-exposure pairs, each captured with its own short time separation, with no overlap between pairs.
Reference	`[A+B], [A+C], [A+D], …`	Comparing every image against one fixed reference frame — e.g. measuring growing displacement relative to a baseline.

Select the sequencing style that matches how your images were captured.
Select the image files in the folder browser and click Add to move them into the Images selected for import list on the right. Use Remove, the move-up/move-down buttons, or Show full paths / Remove duplicates to clean up the list.
Click Import to load them (or Cancel to back out). At least two images — one pair — are required.

PIVlab will double-check your naming If your filenames end in “A” and “B” but you left the style on Time resolved, PIVlab detects the mismatch and offers to switch to Pairwise for you — a common mix-up worth knowing about rather than dismissing without reading.

Odd number of images If your selection results in an odd number of images, the last one is silently dropped so every image can form a complete pair. If that's unexpected, double-check your file selection.

The image list and moving between frames

Loaded frames appear in the Image list, each entry prefixed A: or B: for the first/second image of the pair. To move through frames, use the slider in the Tools panel at the top of the screen (tooltip: “Step through your frames here”), and Toggle to flip between the A and B image of the current frame.

Select one or more entries in the image list and click Remove images to drop them again. At least one pair must remain.

Removing images clears your results Removing images from the list also clears any analysis results, derived parameters and manual vector deletions for the whole session — not just for the removed frames. Do this before analysing, or be ready to re-run ANALYZE! afterwards. If removing leaves an odd number of images, PIVlab highlights the list red and asks you to remove one more.

Sessions vs. settings — what's the difference?

PIVlab has two, easily confused, kinds of saved file. Knowing which one you want avoids a lot of head-scratching:

	Session	Settings
Menu path	File → Load/Save → …PIVlab session	File → Load/Save → …PIVlab settings
Contains	Everything: image references, masks, ROI, calibration, analysis results, and all settings.	Only the configuration — algorithm choice, filter thresholds, colours, calibration setup, etc. No images and no results.
Use it to	Pause and resume the exact same project, or hand off a finished analysis to someone else.	Reuse a processing pipeline you've tuned on a different dataset, or share a configuration without sending any data.
Default file name	`PIVlab_session.mat`	`PIVlab_set_<username>.mat`

Saving and loading a session

Save: File → Save → Save PIVlab session (or the Load session button's counterpart in the menu). Choose a location; the default name is PIVlab_session.mat.
Load: click Load session in the Input data panel, or File → Load → Load PIVlab session. This restores images, masks, results and settings exactly as they were.

Sessions saved with an older PIVlab version PIVlab warns you if a session file was created by an older release, since the interface may have changed since then and some display issues can result.

Saving and loading settings only

Save: File → Save → Save current PIVlab settings. Choose a location; the default name includes your username, e.g. PIVlab_set_yourname.mat.
Load: File → Load → Import PIVlab settings. This rebuilds the interface to match the saved configuration, but does not touch your currently loaded images or results.

PIVlab already remembers a few defaults PIVlab loads PIVlab_settings_default.mat automatically every time it starts, and a handful of individual choices (e.g. Basic/Advanced mode, the last sequencing style you used) are quietly remembered there as you work. That's not the same as saving your whole current configuration, though — use Save/Load PIVlab settings whenever you want a complete, named, reusable configuration you can switch between or share.

Related, but covered elsewhere Acquire images (live camera capture) and Stereo-PIV mode are more specialized topics with their own pages.