Vertical Misalignment & Eye Strain: Diagnose and Fix It in SPM
Of all stereo defects, vertical misalignment is the one your visual system cannot forgive. Your eyes happily converge left-right, but they cannot comfortably look up and down at the same time — so a pair whose images sit at different heights causes strain within seconds. Here is how to recognise it and fix it in StereoPhoto Maker.
Recognising vertical misalignment
- Headache or “pulling” sensation that starts fast and lifts when you close one eye.
- In anaglyph view, horizontal edges show a red/cyan split that is vertical, not horizontal.
- One side’s horizon visibly sits higher than the other in side-by-side view.
The fix: auto alignment
Run Adjust > Auto Alignment. SPM measures and corrects vertical shift along with rotation, size and keystone errors, which usually travel together. Re-check at full size: horizons should be level and matched.
When it keeps coming back
- Shooting technique: a tilted camera or cha-cha shift that also moved vertically. Level the camera; a hot-shoe level or the grid overlay helps.
- Twin rig geometry: cameras mounted at slightly different heights or toe-in angles. Shim the mount, keep axes parallel (twin rig guide).
- Mixed sources: one image cropped or resized differently before pairing. Always pair same-size originals.
Window and depth choices that add strain
Even a perfectly level pair can tire viewers if the stereo window is pushed so the subject floats far in front of the frame, or if the baseline was too wide for the subject distance. Moderate depth is comfortable depth; see the beginner walkthrough for window basics.
If a pair still hurts after alignment measures near-zero vertical error, believe your eyes and retire the pair — subject movement between shots creates local misalignments no global correction can fix.