Definition of "photometrical" []

• Photometric (adjective)

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• "The ratio of the radiant flux with the wavelength Lambda (m) and the radiant flux with the wavelength Lambda both radiations causing the same brightness impression in certain photometrical conditions."
• "Letheby photometer, in order to give your readers an opportunity of estimating for themselves the effect which such variations from the true distance between the standard light and that to be measured, as shown in this series of photographs, must exercise on photometrical observations made by the aid of either of the instruments named."
• "Mr. Defty has sought in the latter to apply the principle of heating the air and gas in a simple manner, with the object of obtaining improved photometrical results."