This is a complete, single-file "Free Photography Flash Duration Motion Freeze Calculator" application. It uses Tailwind CSS for layout, Lucide for iconography, and Inter from Google Fonts for typography. It is fully self-contained, interactive, and mobile-responsive. ```html
Calculate the flash duration required to freeze subject motion with precision.
To freeze motion, the subject must move less than your selected "Allowed Blur" across the sensor during the flash pulse.
We calculate this by determining the magnification ratio (Focal Length / Distance) and comparing it against the subject's velocity.
Note: Always aim for a shorter flash duration than the calculated result to ensure maximum sharpness.