(The TriLux Exposure Meter

Invented by my grandfather, Troy L. Parker, and patented in 1918, the TriLux Exposure Meter was an early form of “extinction meter”. It relied on the perception of light through a tube to measure incidence light. Extinction meters were very popular in the 1920s and early 1930s and remained on sale into the 1950s.

To use this instrument, the user looks into an eyepiece and focuses on a screen. The light reaching the eye is gradually reduced by an iris or density wedge, the meter is set when figures on the screen or part of the scene becomes indistinct. A problem with extinction meters was the eye’s ability to adapt to changing light levels. When looking into the eyepiece the eye will start to compensate for the lower level of light, the adaptation time varies but could take 30s or more.

A true American collectible, the TriLux Meter is once again available in new packaging, with a copy of the original user manual. The manual is also available as a pdf, here. A copy of the original patent is available to view, here.

The price of $24 includes one wrapped light meter, a copy of the original instruction sheet, and USPS ground shipping and handling. (The appearance of the light meter and tissue wrap may vary from unit to unit, as these are over 100 years old, and can exhibit some tarnishing, or surface defects.)