Four pairs,
four known answers
Each pair below was generated with an exact transform applied on purpose, so the numbers printed under it are the truth and not an estimate. Open one in Drift and compare what the tool reports against what was actually done.
What makes a good pair
Same scene, twice
Drift measures how one frame moved relative to the other. Two unrelated photographs give it nothing to lock onto. It checks how far the correlation peak stands above the rest of the surface and warns you when nothing clearly wins — a useful guard, though not a guarantee.
Mostly unchanged
The alignment is read from what stayed the same. If more than roughly half the frame is different, there is no longer a dominant shift to find.
Brightness can differ
One photo darker, or shot at a different exposure, is fine — the method throws the magnitude away and keeps only phase. Turn the sensitivity down if an exposure change starts painting the whole frame red.