Alignment matters more than the slider
A reveal comparison is most useful when both files show the same crop and camera position. Large alignment differences make local changes harder to judge.
Check for accidental resizing
Before judging subtle detail, confirm both pixel dimensions. An edit can look softer simply because one result was exported smaller.
Inspect representative areas
Move the divider through fine texture, edges, skin, gradients, and compression-prone backgrounds rather than judging from one central region.
File size is not quality by itself
A smaller file can be visually excellent, while a larger file can contain inefficient encoding. Compare visible detail and artifacts alongside bytes.
Use a difference heatmap for aligned images
When two files have identical pixel dimensions, a sampled pixel-difference pass can quantify changed pixels and generate a heatmap. Use it to locate edits, compression artifacts, restoration changes, or retouching—not as an automatic visual-quality score.
- Mean absolute error summarizes average RGB change.
- RMSE weights larger channel changes more strongly.
- A thresholded changed-pixel percentage helps ignore tiny encoding noise.