Auto Alignment in StereoPhoto Maker (and StereoAutoAlign)
No hand-held stereo pair comes out of the camera aligned. The two shots always differ a little in height, rotation, size and perspective, and those small errors are exactly what makes a stereo image tiring to look at. StereoPhoto Maker’s auto alignment measures and corrects them. This guide explains what it fixes, how to run it on one pair, and how the companion tool StereoAutoAlign handles whole folders.
What auto alignment corrects
- Vertical disparity — one image sitting higher than the other; the single biggest cause of eye strain.
- Rotation — one camera tilted slightly relative to the other.
- Size mismatch — usually from a zoom difference or focus breathing between shots.
- Keystone distortion — the trapezoidal error from converging the cameras (toeing-in) instead of keeping them parallel.
SPM reports the corrections it applied, so you can see whether a pair needed a nudge or a rescue. Large corrections are a shooting-technique signal, not a software failure — see the twin rig and cha-cha workflow guides.
Aligning one pair
- Open the left/right pair (or an MPO file) in SPM.
- Run Adjust > Auto Alignment. SPM analyses the pair and applies the corrections.
- Inspect the result at full size in anaglyph or side-by-side mode: straight edges should sit at the same height in both views.
- Save the aligned version as your master (File > Save Stereo Image) before making viewing copies.
StereoAutoAlign: alignment for whole folders
StereoAutoAlign is a separate command-line companion by the same author, designed to work alongside SPM. Trigger it from SPM with Shift+A, or use it in batch mode to process folders of pairs unattended. Since v6.19, if a file renamed to Exiftool.exe sits in the SPM folder, StereoAutoAlign batch runs can also copy EXIF data from the original files to the aligned outputs — the trick behind keeping metadata through a batch, covered in the EXIF guide.
StereoAutoAlign’s command-line options are its own. SPM itself has no command-line switches — claims of flags like -autoalign or -sbs for SPM are made up.
When alignment cannot save a pair
- The subject moved between shots (people, animals, foliage in wind).
- One side is blurred or exposed very differently.
- The baseline was far too wide for the subject distance, creating depth no correction can compress.
In those cases the honest fix is a reshoot. If vertical error survives alignment, work through the vertical misalignment guide before blaming your eyes.