Carlos de Haes

According to Wikipedia, Carlos de Haes (Belgian/Spanish, 1829–1898) "believed that the end result of art should be the truth found in the imitation of nature, the source of all beauty."

"The painter should imitate nature as closely as possible, and to do so, you must know nature and not rely on imagination. Leaving behind Romanticism, he was early to embrace the en plein air style, working from outdoor preparatory sketches which were completed within a workshop."
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Carlos de Haes on Wikipedia