ஒளிப்படவியல்: திருத்தங்களுக்கு இடையிலான வேறுபாடு

[[படிமம்:Nicéphore_Niépce_Oldest_Photograph_1825.jpg|இடது|thumb|Earliest known surviving heliographic engraving, 1825, printed from a metal plate made by [[Nicéphore Niépce]].<ref name="utexas">{{cite web|title=The First Photograph – Heliography|url=http://www.hrc.utexas.edu/exhibitions/permanent/wfp/heliography.html|quote=from Helmut Gernsheim's article, "The 150th Anniversary of Photography," in History of Photography, Vol. I, No. 1, January 1977: ...In 1822, Niépce coated a glass plate... The sunlight passing through... This first permanent example... was destroyed... some years later.|accessdate=29 September 2009}}</ref> The plate was exposed under an ordinary engraving and copied it by photographic means. This was a step towards the first permanent photograph taken with a camera.]]▼