A one-degree tilt is worse than a ten-degree one. At 10° the viewer reads it as a deliberate dutch angle; at 1° they just feel that something is subtly wrong. That's why straightening is one of the highest-value, lowest-effort edits.

Pick the Right Reference Line

Straightening works by choosing a line in the photo that *should* be level or plumb, then rotating until it is:

  • Landscapes: the horizon, or the waterline. Water is always level — trust it above anything else.
  • Architecture and interiors: vertical edges (door frames, window frames, corners of rooms) are usually more reliable than horizontal ones, because floors and ceilings are affected by perspective.
  • Documents and screenshots: the text baseline or the paper edge.
  • Portraits: a background vertical, not the person — people lean, and forcing a person vertical often tilts the whole world.

Never straighten to a sloping road, a hillside or a table that might genuinely be uneven.

Know the Cost

Rotating by a non-90° angle does two things:

  1. It resamples the image. Pixels are recalculated, which softens fine detail very slightly. It's usually invisible, but it means straightening should be done once, from the original, not repeatedly.
  2. It requires cropping. Rotating leaves empty triangular corners, so the editor crops inward. A 2° correction costs roughly 3–5% of the frame; 5° costs over 10%. Anything already tightly composed may lose important edges.

So: straighten before you do the final crop, and shoot slightly wider than you need when you know the scene has a strong horizon.

Converging Buildings Are a Different Problem

If a building leans *inward at the top*, that's not tilt — it's perspective distortion from pointing the camera upward. Rotation can't fix it; you need perspective correction (keystone correction), which stretches the top or bottom of the frame. It costs even more pixels than rotation, and overcorrecting makes buildings look unnaturally wide at the top. Correcting about 80% of the convergence usually looks more natural than a perfectly parallel result.

Getting It Right In-Camera

  • Turn on your camera or phone's grid and level indicator. Both are free and eliminate the problem entirely.
  • Watch the horizon, not the subject, in the split second before the shutter.
  • For documents, shoot from directly overhead and align the paper edges to the screen edges — a straight capture also avoids the resampling cost above.

One last note: if a photo was straightened and cropped, keep the original. Straightening choices sometimes look different a day later, and re-rotating an already-rotated, already-cropped file compounds both costs.