While Realism and Impressionism were styles born apart around the mid 19th century, they eventually merged around the end of that century in the work of some artists, notably among them Joaquín Sorolla in Spain and John Singer Sargent in the United States.
The main difference between Impressionist Art and Realist Art is that the first is more focused on the effect of atmospheric light while the second places more importance on the subject represented. Both styles are inspired by what artists saw around them, as opposed to Classical or Romantic Art which produced large paintings of imaginary visions from the past.
Realist painters and Impressionist painters practiced what is known as “plein air”, a french term meaning painting in the “open air”, outside of the studio. Up until then, the common practices for artists were to create drawings and paintings from plaster casts or models at the academies or ateliers and to do quick pencil sketches outdoors. The finished work was done at the studio. Realist painters brought their easels and paints to the field, but most preferred to finish their paintings inside the studio. Impressionists artists were more concerned with the actual moment and opted to capture “impressions” of an scene and attempted to complete the painting right then and there.
A principal difference between Impressionism and Realism as styles of painting is the method of rendering light and shade, or values. Realist artists kept to the “academic” method of adding luminosity to a color by mixing it with white or darkening it with a brown or black pigment. Impressionist artists, on the other hand, developed a technique based on the value quality of the pigments themselves, using high value colors like yellow for their lights and dark value colors like violet or dark blue for their darks. It wasn’t meant to be that simplistic, of course, as white was used and colors were combined to form various lighter and darker tones, but the Impressionist tended to avoid black pigment like the devil.
When some realist painters, like the two mentioned above, decided to apply the new color theory of the Impressionists, a new form of realism was born. To these days, a great number of artists continue to follow this legacy and produce contemporary realist paintings that blends the best of both Realist and Impressionist styles.