In 1888, Ferdinand Hurter and Vero Charles Driffield patented a device for estimating the actinic power of sunlight and for computing exposure times and apertures for cameras, based on the plate speed, time of day, time of year, and latitude.
After experimenting with more advanced methods of additive systems (including a camera with two apertures (one with a red filter one with green) from 1915 to 1921, Dr. Herbert Kalmus, Dr. Daniel Comstock, and mechanic W. Burton Wescott (who left the company in 1921) developed the subtractive color system for Technicolor.
Potassium channels and pumps have been identified and shown to function in the uptake of ions and opening of stomatal apertures (Figure 2).
It is operated and maintained by the Instituto de Astrofísica de Andalucía (Institute of Astrophysics of Andalusia - IAA) and contains two Nasmyth telescopes with apertures of 1.5 and 0.9 metres.