Photography planning · browser-local depth geometry · 2026 · Solo — product framing, test-first optical math, interaction design, accessibility, responsive verification, production deployment
Depth Slate
A field-depth instrument that shows whether two physical subject planes can share acceptable focus before the tripod is locked.
The problem
Photographers staging a landscape, interior, or product frame often know the nearest and farthest subject distances but still have to translate those planes into an aperture and focus placement. A depth-of-field table can supply limits, yet it leaves the actual subject span detached from the result and makes a missed near or far plane easy to overlook. Depth Slate keeps that bounded decision causal: choose a conventional sensor format, focal length, aperture, and focus distance; place the two target planes; then read the near limit, focus plane, far limit, hyperfocal threshold, and subject bracket on one shared rail before copying the exact setup as a field note. The thin-lens result uses conventional circles of confusion and is a planning aid rather than a lens-specific sharpness guarantee; diffraction, aberrations, focus breathing, field curvature, camera tilt, subject motion, print size, and viewing distance remain outside its model. Values stay in ephemeral browser state; there is no image upload, account, persistence, paid API, tracking SDK, outbound email, advertising, payment, or destructive operation. Production deployment dpl_DAYG1TwnKPARPDnUk7yM1dkCd8HQ reached READY before independent Foundry HTTPS marker and nine-step behavior checks passed at the stable alias.
Architecture
Key decisions
Make physical depth the operating surface
The rail is not a decorative chart. Near limit, focus plane, far limit, acceptable band, and target pins all derive from the same tested setup, so moving a subject or optical control produces one inspectable geometric consequence.
Keep acceptable focus honest
Depth Slate names the selected circle of confusion, labels the equation as conventional thin-lens guidance, and asks for confirmation on the actual camera at intended output size rather than claiming measured lens sharpness.
Use premium engineering principles without cloning a brand
Light uppercase display type, sharp geometry, dark/light showroom rhythm, and a single interaction blue establish precision, while the custom depth rail, acid target pins, optical stack, and copy tone remain original to the photography workflow.
Treat every operating state as part of the instrument
The release probe exercised empty, validation-error, loading, success, and clipboard-receipt states. Reduced-motion CSS removes nonessential transition timing while native controls preserve keyboard operation and visible focus.
Let verification failures improve the evidence
A compressed mobile capture exposed a label collision and the release probe exposed an ambiguous ARIA test selector plus a stale local server child. The caption was removed at the mobile breakpoint, the probe was made exact, and the final build and all local gates were rerun serially.