Jacob van Ruisdael – National Gallery of Art 1961.9.85. Landscape (c. 1670)
Materials: oil on canvas. Dimensions: 53.2 x 60 cm. Inscriptions: JvR (in ligature, lower center on rock to left). Nr.: 1961.9.85. Source: http://www.nga.gov/content/ngaweb/Collection/art-object-page.46184.html. I have changed the contrast of the original photo.
Canaletto – National Gallery of Canada 3718. St. Mark’s and the Clock Tower, Venice (c. 1735-1737)
Materials: oil on canvas. Dimensions: 132.8 x 165.1 cm. Acquisition date: 1930. Nr.: 3718. Source: https://fbcdn-sphotos-c-a.akamaihd.net/hphotos-ak-ash2/t1/425888_496560447029607_2000468253_n.jpg. I have changed the light, contrast and colors of the original photo.
elsewhere 
