# Thirty-Six

> Plan a roll of film before you shoot it. List the shots for an outing and see the roll as a contact sheet: which frames the film speed and camera can expose, which need the flash, which will come out too dark or washed out, and whether the shots fit 12, 24, 27, 36 or 72 exposures. A metered critic then calls the roll ready, rebalance or wrong film, re-allocates the frames and writes a composition note for every group.

URL: https://thirty-six.skillsafe.ai/

## What is free (runs in the browser)

- The roll: film speed (ISO 50-3200), film type (colour negative, black and white negative, slide), exposures, and a camera class (point-and-shoot compact, single-use camera, manual SLR or rangefinder) with editable specs.
- The shot list: groups of frames with a subject, a light condition (13, from sun on snow to candlelight), a distance and how much the subject moves.
- Exposure estimates per group: scene brightness from the classic exposure-value table, the aperture and shutter the camera can reach, stops over or under, flash reach from the guide number, and the film's latitude.
- The frame budget, the film speed that would save the most frames, and the contact sheet itself.
- Exports: Markdown plan, frames CSV, roll JSON, contact sheet SVG, a printable pocket plan.

All light levels, latitudes and camera specs are typical values - estimates for planning, not meter readings.

## What is metered

One task, `plan`, billed in SkillSafe credits to a signed-in account. Input: `task`, `outing`, `iso`, `film_type`, `frames`, `camera`, `camera_spec`, `shots`, `facts` (JSON-encoded). Reply: one JSON object with `verdict` (`ready` | `rebalance` | `wrong-film`), `verdict_why`, `title`, `groups` [{id, frames, mark: keeper|maybe|cut, composition, exposure, cite}], `swaps`, `film_advice`, `tips`, `caveats`. The page checks every reply against the roll before it can be applied.

API docs: https://thirty-six.skillsafe.ai/api.html

## Source

The critic is built on the SkillSafe skill @curiositech/photo-composition-critic (https://skillsafe.ai/skill/@curiositech/photo-composition-critic): composition critique by visual weight, figure-ground, eye flow, light quality and genre-appropriate standards.