Film Latitude Lock auto-constraint
Constrain the solver to stay inside the loaded film's latitude; not yet wired.
Summary
Planned constraint that keeps every alternative exposure pair the solver offers within the loaded film's usable latitude. The FilmLatitude enum already labels each stock with a stop range; the lock toggle that enforces it during alternative-pair generation has not shipped.
How it works
Current limitations
The FilmLatitude enum is in place and each film entry carries an explicit stop range (e.g., Velvia 50 has a tight 5-stop range; Portra 400 has roughly 9 stops). What is missing is a Lock toggle that, when enabled, prunes the solver's alternative aperture/shutter pairs so none of them place the key tone outside that range.
What's planned
Add a Film Latitude Lock toggle to the Viewfinder priority controls. When the lock is on, the solver still produces an exposure recommendation, but every adjacent pair (the next stop wider, the next stop slower, etc.) is checked against the current film's latitude and any pair that would push the key tone past the latitude is hidden or marked unsafe. Slide film users get a hard rail; negative film users get a soft warning.
Why MEDIUM priority
The information already exists, the solver already produces alternative pairs (1.8 and 1.9 use this), and zone-system users routinely ask for a 'do not let me clip' guarantee. Wiring the constraint through the alternative-pair generator is contained work that delivers a real safety net on slide film and on heavily pushed stock.