Handheld light meters are designed to give a larger range of exposure, aperture, and shutter speed settings for film photography. This is particularly helpful for photography tips and techniques like winter photography and night photography as the handheld meter will help determine the proper length of exposure time.

Your camera’s built-in reflective light meter is very accurate. It evaluates the light reflecting from the entire scene with the goal of avoiding overexposure. This is fine for digital, where our goal is avoiding overexposure (blown-out highlights). Your matrix or evaluative meter is also an excellent tool for exposing transparency film. Again, like with pixels, the goal is to avoid overexposure.

Properly exposing negative film requires a completely different approach. Whilst negative film has tremendous latitude, proper exposure is still important for consistent results. Rather than using a meter that evaluates the amount of light reflecting from the subject, we need a meter that can measure the brightness of the shadow area in our image. We want to allow enough light to pass through the aperture and shutter of our camera to properly expose for shadows, not the highlights. This allows film density to build and prevents underexposure. Failure to allow enough light to reach the film often results in muddy, underexposed negatives and poor quality prints.

But the digital light meters on the market are too expensive, and the analog ones are not so accurate and are not always convenient to use.

I want to present you an exposure meter that is fairly cheap, accurate and has all the necessary functions. The lightmeter based on Arduino as a main controller and BH1750 as a metering cell. Information is displayed on SSD1306 OLED display. The device is powered by 2 AAA batteries.

Functions list:

  • Ambient light metering
  • Flash light metering
  • ND filter correction
  • Aperture priority
  • Shutter speed priority
  • ISO range 8 – 4 000 000
  • Aperture range 1.0 – 3251
  • Shutter speed range 1/10000 – 133 sec
  • ND Filter range ND2 – ND8192
  • Displaying amount of light in Lux.
  • Displaying exposure value, EV
  • Recalculating exposure pair while one of the parameter changing
  • Battery information
  • Power 2xAAA LR03 batteries

Project page on Github: https://github.com/vpominchuk/lightmeter