Horizon and lens projection
Plot the same geometric horizon through three camera projections. Change camera pitch and field of view to see how a misplaced horizon and a wide-angle lens alter the displayed line.
Each line uses horizon dip 0°, camera pitch 10° and a 100° horizontal field. The coordinate scale is shared, so the lens models can be compared without stretching each line separately.
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Image radius: tan θ, θ, or 2 sin(θ/2)
The diagram projects rays onto a normalized image plane: rectilinear uses tan θ, equidistant uses θ and equisolid uses 2 sin(θ/2). All three receive exactly the same horizon directions.
A photograph needs the lens projection, calibration and camera orientation before its line shape can be compared with this plot. Keep the original image and its lens information alongside any edited version; the calculator changes ray projection rather than rewriting a photograph.