Hotshoe-Mounted Light Meter

Alex Hao


  • A portable light meter that mounts to the camera via hot shoe.

  • Many vintage film cameras don’t have built-in light meter, and eye-balling exposure can be very inaccurate.

  • User can set aperture and ISO, then the meter can display correct shutter speed.


Technical Overview


  • ESP32-S2-SOLO-U (w/o antenna)

  • Ambient light sensor and OLED display that talk via I2C

  • Powered by 105 mAh LiPo battery

  • Two rotary encoders with push buttons as input

    • Since film stocks have fixed ISO, it doesn’t need to be changed frequently

    • At the press of a button, ISO or Aperture setting can be locked to prevent accidentally changing it!


Base board

With buttons and knobs

Two-Piece shell for mounting and shielding for the light sensor

Mounted on the Leica MP film camera

Coming next version...

    • Smaller microcontroller (e.g. STM32)

    • USB charging functionality

    • Lower power consumption & longer battery life

    • Even more compact form factor