Field of View (FOV) and Image Format

Field of view is the object-space angular range imaged in a given direction. It is commonly reported as horizontal (HFOV), vertical (VFOV), and diagonal (DFOV). For an ideal rectilinear lens viewing a distant object, θ = arctan(Y′/f), so full angle is 2θ = 2 × arctan(Y′/f). Y′ is the half-size from image center to the relevant edge; with full width W, HFOV = 2 arctan(W/(2f)). Fisheye and ultra-wide lenses may use different projection models, so the rectilinear equation may not apply.

In the far-field approximation, coverage width at working distance L is about 2L tan(HFOV/2). At finite conjugates, magnification, principal-plane location, and focus breathing also matter. Specifications should distinguish angular FOV, actual width/height at a stated working distance, and the maximum object field that meets image-quality requirements.

“Acceptable field diameter” may mean the image-side image circle over which quality is acceptable, or the object-side field diameter at a particular working distance. These are different quantities. For sensor matching, confirm that the image circle covers the sensor diagonal. For scene coverage, confirm object-space diameter or width/height at the stated distance. Define acceptable corner performance using MTF, illumination, distortion, chromatic aberration, and usable-pixel criteria.

Start with the active sensor dimensions and target working distance, then estimate a focal-length or FOV range. Check projection model, distortion, edge illumination, resolution, and mechanical envelope. In measurement applications, edges are often the most challenging region; validate center, 70% image height, and full field.