The Tempophot Light Exposure Meter is a handheld photovoltaic selenium cell light exposure meter manufactured by the German engineering company Metrawatt AG in Nuremberg, Germany. Originally introduced around 1935, it features a mechanical calculator dial, a built-in swivel baffle / resistor shunt for varying light conditions, and a needle indicator to determine correct film exposure.
Key Features:
- Maker: Produced by Metrawatt AG (which later merged into Gossen-Metrawatt).
- Casing Material: Features a distinct, heavy-moulded Bakelite housing.
- Sensory Technology: Uses a built-in selenium photocell. This cell generates its own low-voltage electrical current when exposed to light, meaning the meter does not require batteries to function.
- Baffle / Shunt Control: A side button adjusts the meter cell mechanism, allowing the needle to point to specific indicator numbers on an internal scale.
- Calculator Dial: Integrates old European film speed standards (such as DIN or Scheiner) with matching shutter speed and aperture scales
How It Works
1. Set Film Speed: Rotate the central dial calculator to match your film's sensitivity, which was originally marked in older European DIN or Scheiner scales (though some export variants use ASA/ISO).
2. Take a Reading: Point the meter at your subject; the internal selenium cell moves a physical needle across a numerical scale.
3. Engage the Meter: Pressing the physical button on the side drops the interior meter cell mechanism into position. The internal needle will swing across a scale of numbers based on the light intensity.
4. Match Needle and Index: Turn the calculation wheel until the index line or inner dial aligns with the needle position to read compatible shutter speed and f-stop combinations.
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