Match Rectilinear Horizontal Framing with Active Sensor Widths — Free
Two camera modes can use different active sensor widths even when their lens labels look close. Match horizontal angle explicitly before describing a multi-camera framing plan as equivalent.
The proof surface
Shutter-angle tools calculate exposure time. These cards calculate ideal rectilinear horizontal field angle and a reference-matching focal length from active width. They do not infer aperture, depth of field, perspective or a camera's actual recording crop.
InputCamera setup | active sensor width (mm) | actual focal length (mm); chosen reference horizontal field angle (degrees)
Rare deviceShutter-angle tools calculate exposure time. These cards calculate ideal rectilinear horizontal field angle and a reference-matching focal length from active width. They do not infer aperture, depth of field, perspective or a camera's actual recording crop.
Output artifactLargest absolute horizontal-angle mismatch with row-by-row context
Cost$0 local calculation · no card, paid key, subscription or signup · proposed filing price is not for sale
Sample, not your facts: Illustrative inputs: Camera A | 36 | 50; Camera B | 24 | 35. Chosen reference horizontal field angle (degrees) = 90. Largest absolute horizontal-angle mismatch: 52.150711 degrees absolute mismatch. All records are invented.
Before using the field-angle card
Use the physical width of the sensor region active in the selected recording mode, not a diagonal sensor size or a nominal crop factor unless converted and verified separately. The formula assumes a rectilinear ideal lens focused under a suitable geometric model. Fisheye mapping, distortion correction, anamorphic desqueeze, focus breathing and digital stabilization crops can invalidate it. Sensor width and focal length must be positive millimeter quantities. The chosen reference angle lies strictly between zero and 180 degrees. Rows are alternative camera setups, and the summary is the largest absolute angular mismatch, not a sum of angles or a quality rating. A matching focal length is a mathematical target, not proof that an available lens can provide the framing.
Why the flat version breaks
Entering equivalent focal length twice
An equivalent focal label already encodes a format convention. Combining it with the physical active sensor width can apply a crop adjustment again. Use actual focal length and actual width, or obtain a separately verified conversion before entering the row.
Using the full sensor for a cropped mode
The horizontal angle depends on the active recording region. A mode that uses less than the full width narrows framing at the same lens focal length. The calculator cannot identify a mode from a camera name; verify the width for the specific mode instead of accepting a plausible generic specification.
Calling angle match an image match
Perspective depends on camera position, and distortion and focus breathing can alter real framing. A ninety-degree horizontal match does not guarantee vertical coverage, exposure or depth-of-field equality. Keep the geometric target separate from the actual production test.
How to work the field-angle card
Confirm the active recording width
Look up or measure the sensor region used by the exact video or still mode and retain its source. A full-width mode and a cropped high-frame-rate mode may need separate rows. Do not use diagonal dimensions as horizontal width. Setup codes are sufficient; no footage, equipment serial number or location data is uploaded.
Use actual focal length and one reference angle
Enter the lens's modeled physical focal length in millimeters, not a full-frame-equivalent label. Choose the reference horizontal angle from a verified framing plan. If the source only provides a crop-factor equivalent, reconcile that convention outside this tool rather than mixing it with an active physical width.
Calculate angle and matching focal length separately
Current angle is 2×atan(active width/(2×focal length)), converted from radians to degrees. A focal length matching reference angle A is width/(2×tan(A/2)). The card retains the signed angle difference while the summary takes its largest absolute magnitude. Small floating-point residuals are displayed with six-decimal rounding, not treated as equipment measurement precision.
Verify framing with the actual camera mode
Test the setups against a suitable framing chart or scene at controlled camera position. Ask a camera technician about distortion, breathing or crop modes if the result differs. Matching horizontal field angle alone does not match perspective when camera positions differ, and it does not make exposure or depth of field equivalent.
What the field-angle card separates
Question
Before
Inspect this instead
Entering equivalent focal length twice
An equivalent focal label already encodes a format convention. Combining it with the physical active sensor width can apply a crop adjustment again. Use actual focal length and actual width, or obtain a separately verified conversion before entering the row.
Use actual focal length and one reference angle
Using the full sensor for a cropped mode
The horizontal angle depends on the active recording region. A mode that uses less than the full width narrows framing at the same lens focal length. The calculator cannot identify a mode from a camera name; verify the width for the specific mode instead of accepting a plausible generic specification.
Calculate angle and matching focal length separately
Calling angle match an image match
Perspective depends on camera position, and distortion and focus breathing can alter real framing. A ninety-degree horizontal match does not guarantee vertical coverage, exposure or depth-of-field equality. Keep the geometric target separate from the actual production test.
Verify framing with the actual camera mode
This field-angle card replaces a manual count or calculation, not source verification or the responsible person’s review.
Run it on the samples, right here
FIRST-LOAD
HYPOTHESIS / PROTOTYPE — checkout unavailable. Calculation is local. A draft is saved automatically in this browser profile when storage is available; Reset to sample clears it. Optional Pro history stores only five summaries and has its own deletion control. State links encode your inputs and can remain in browser history, clipboard or recipients’ records; share only non-sensitive rows. Optional external AI formatting leaves this device. The required site analytics beacon reports page activity; shared URLs contain encoded inputs. Do not treat an encoded URL as private. The calculator has no input-collection endpoint.
Ideal rectilinear framing geometry only, not an equipment-performance guarantee. Confirm active recording dimensions and test actual framing; ask a qualified camera technician about crops, distortion, breathing or anamorphic modes before a consequential shoot.
Data note: The field-angle card processes Camera setup | active sensor width (mm) | actual focal length (mm) locally. Starter/sample selection and Run compute in this tab; no input is sent by the calculator. A local draft may be saved; explicit state-link sharing or optional external AI formatting can disclose inputs. Use non-sensitive labels.
Go deeper: the companion app files the same reading as a index card with a stamped header
The article demo above runs without limits. The companion app keeps a local history, exports the rows as CSV, prints the field-angle card reading, and holds your drafts on this device — one complete free app run; the proposed $4 one-time filing layer is not for sale.
The field-angle card answer stays complete for free. The proposed $4 one-time filing layer adds row CSV, print and five local reading summaries, not hidden answers. Checkout is unavailable; the article demo remains unlimited.
Ideal rectilinear framing geometry only, not an equipment-performance guarantee. Confirm active recording dimensions and test actual framing; ask a qualified camera technician about crops, distortion, breathing or anamorphic modes before a consequential shoot.
What this is built on
Method: Current angle is 2×atan(active width/(2×focal length)), converted from radians to degrees. A focal length matching reference angle A is width/(2×tan(A/2)). The card retains the signed angle difference while the summary takes its largest absolute magnitude. Small floating-point residuals are displayed with six-decimal rounding, not treated as equipment measurement precision.
All sample records, dates, quantities and labels are invented. No outside policy, contract, rate, clock offset, measurement or accessibility standard is represented as verified.
Google’s official pricing documentation, fetched 2026-10-01, says AI Studio is free in available regions. Optional formatting may require a Google account; manual local entry requires none. Limits can change and free-tier content may be used to improve products. Do not send private records.
Before: lens labels were assumed to mean matching coverage. After: active width, current angle and a reference-matching focal length are separate production quantities.
For Camera A, 2×atan(36/(2×50)) gives 39.597753 degrees. Camera B's 24 mm active width and 35 mm focal length give 37.849289 degrees. Relative to the supplied ninety-degree reference, their absolute gaps are 50.402247 and 52.150711 degrees. The latter is the summary. Matching ninety degrees would require modeled focal lengths of 18 mm and 12 mm respectively, without changing any lens's physical focal length.
Wide's ratio is one, so its horizontal field angle is ninety degrees and its gap is zero. Bridge's ratio is one half, giving 53.130102 degrees and a 36.869898-degree gap. The card provides a target focal length for each active width, not a crop-factor slogan. An actual camera mode may use a smaller width than its full sensor, so source dimensions still matter.
A 36 mm active width paired with an 18 mm rectilinear focal length gives exactly ninety degrees in this ideal geometry, matching the supplied reference. Zero angle mismatch says nothing about distortion, camera distance, depth of field, focus breathing or vertical framing. Those can differ even when the horizontal-angle calculation agrees.
Optional AI formatting, never the calculation
Manual entry completes this field-angle card for free without signup. If available to you, the free AI Studio interface linked in the sources may format fictional or non-sensitive notes; external access may require an account. No API key or AI call is built into this tool. Free-tier content may be used to improve products. Review each cell and transcribe it to the labeled row schema; do not paste the JSON object into the row box.
Format only these fictional or non-sensitive notes for a field-angle card. Return strict JSON shaped as {"rows": [{"label": "string", "cells": ["string", "string"]}], "setting": "string"}. The columns are Camera setup | active sensor width (mm) | actual focal length (mm); the setting is Chosen reference horizontal field angle (degrees). Keep all supplied strings and quantities exactly; do not calculate, infer missing entries, invent dates or add advice. If any required value is missing, return an empty rows array and ask me for it separately. I will verify every cell against my source and manually transcribe rows using vertical bars before running the local calculator.
An AI response is not executed, fetched or trusted as a result. Missing values remain questions; the strict local parser checks the rows you actually enter.