Editing Rod cell (section)

===Sensitivity===
A rod cell is sensitive enough to respond to a single [[photon]] of light<ref name="Okawa">{{cite journal|last=Okawa|first=Haruhisa|author2=Alapakkam P. Sampath |title=Optimization of Single-Photon Response Transmission at the Rod-to-Rod Bipolar Synapse|journal=Physiology|year=2007|publisher=Int. Union Physiol. Sci./Am. Physiol. Soc.|volume=22|issue=4|pages=279–286|doi=10.1152/physiol.00007.2007|pmid=17699881}}</ref> and is about 100 times more sensitive to a single photon than cones.  Since rods require less light to function than cones, they are the primary source of visual information at night ([[scotopic vision]]). Cone cells, on the other hand, require tens to hundreds of photons to become activated. Additionally, multiple rod cells converge on a single [[interneuron]], collecting and amplifying the signals. However, this convergence comes at a cost to visual acuity (or [[image resolution]]) because the pooled information from multiple cells is less distinct than it would be if the [[visual system]] received information from each rod cell individually.
[[File:Cone-response-en.svg|thumb|300px|right|Wavelength absorbance of short (S), medium (M) and long (L) wavelength cones compared to that of rods (R).<ref>{{cite journal|author=Bowmaker J.K. and Dartnall H.J.A.|pmc=1279132 |title=Visual pigments of rods and cones in a human retina|journal=J. Physiol.|pmid=7359434|volume=298|pages=501–511|year=1980|doi=10.1113/jphysiol.1980.sp013097}}</ref>]]

Rod cells also respond more slowly to light than cones and the stimuli they receive are added over roughly 100 milliseconds. While this makes rods more sensitive to smaller amounts of light, it also means that their ability to sense temporal changes, such as quickly changing images, is less accurate than that of cones.<ref name="Kandel">Kandel E.R., Schwartz, J.H., Jessell, T.M. (2000). ''Principles of Neural Science'', 4th ed., pp. 507–513. McGraw-Hill, New York.</ref>

Experiments by [[George Wald]] and others showed that rods are most sensitive to wavelengths of light around 498&nbsp;nm (green-blue), and insensitive to wavelengths longer than about 640&nbsp;nm (red). This is responsible for the [[Purkinje effect]]: as intensity dims at twilight, the rods take over, and before color disappears completely, peak sensitivity of vision shifts towards the rods' peak sensitivity (blue-green).<ref>{{cite journal |last1=Wald |first1=George |title=Photo-labile pigments of the chicken retina |journal=Nature |date=1937b |volume=140 |issue=3543 |page=545 |doi=10.1038/140545a0|bibcode=1937Natur.140..545W |s2cid=4108275 }}</ref>