ABOUT
A useful geometric sketch.
A small, focused calculator for an entered ideal camera model.
One question, one calculator
Viewframer is an independent free geometry tool for people comparing ideal camera framing or learning how a recorded rectangle relates to focal length. It calculates horizontal, vertical and diagonal full angles, then optionally projects that same rectangle onto a perpendicular plane at a clearly defined axial distance.
It does not identify a camera, collect a photo, infer an active sensor crop, inspect EXIF or measure a real lens. A useful result depends on entering an active physical rectangle and understanding the ideal distance reference.
How it works
The calculator runs in your browser. Required physical lengths and optional distance are stored as rational values for stable unit conversion. Trigonometric angles and diagonals are numerical approximations. The guide explains the assumptions and supplies worked examples you can reproduce.
The tool was checked with independent similar-triangle and inverse-angle comparisons, unit-switch invariants, invalid and reset cases, and current-report export handling. Those source checks do not replace physical camera calibration or establish a browser/device test that has not been performed.
Free access and advertising
You can use the calculator and local reports without payment or an account. This initial release has no active advertising, analytics or consent-management loader. Publisher ownership metadata and ads.txt prepare the site for possible future advertising; they do not mean Google has approved it or that ads are serving. Any later loader changes require corresponding privacy and consent coverage.
Corrections
Found a wrong assumption or reproducible calculation problem? Use the public contact address and include the entered values and units. Do not send private photos or personal camera-account details. We share this forwarding address with other tools and have not created a separate mailbox for this site.