= Selig Hecht
{c}
<Selig Hecht> was a researcher in the physiology of <vision> who measured how sensitivity changes during <light adaptation> and <dark adaptation>. In a 1937 study, <Selig Hecht> and colleagues varied prior illumination and then measured recovery of the human eye's ability to detect faint test lights.<The influence of light adaptation on subsequent dark adaptation of the eye by Selig Hecht and others>[Original byline and Abstract: preadaptation and recovery measurements]{ref}
The recovery curve depended on the preceding exposure. Under sufficiently bright preadaptation, an early phase associated with <cone cells> was followed by a slower phase associated with <rod cells>; other exposure conditions did not reveal both phases in the same way.<The influence of light adaptation on subsequent dark adaptation of the eye by Selig Hecht and others>[Introduction, Rod and Cone Adaptation; Abstract]{ref}
This makes prior conditions part of the experiment. Two observers tested after the same time in darkness need not be in comparable states if their preceding illumination differed. A curve measured over time reveals changes that a single final sensitivity measurement would hide. The historical illumination unit called photons in this paper should not be interpreted as a count of individually detected <photons>.
Back to article page
