Take one reference photo first

Photograph the entire target before moving it. Keep the camera centered over the paper and avoid a steep angle. The full image preserves target identity and gives the crop tool enough context.

Control the simple problems

• Use even light without hard glare
• Keep the target flat
• Include a ruler or known printed dimension
• Avoid fingers, tape, and marker lines over the impacts
• Use the search-area tool when the sheet has several groups

Automatic detection is a starting point

Paper tears, splatter targets, old pasters, and printed graphics can all look like impacts. Review every detected marker, add anything missed, remove false positives, and then set scale.

The saved result should reflect what you verified, not just what an algorithm guessed.