The painting above is "Dennis Miller Bunker Painting at Calcot" by John Singer Sargent (1888). Dennis Miller Bunker (1861-1890) lived just 29 years, but showed considerable promise, as Sargent seemed to have realized.
Some biographical information is here, and some of Bunker's thoughts regarding being an artist can be found here.
Bunker was a solid traditional/representational painter who spent a year or two in France when French Impressionism was gaining acceptance and Post-Impressionism was getting underway (Manet died in 1883 and Seurat was about to paint his masterpiece, "Un dimanche après-midi à l'île de la Grande Jatte"). He made some oil sketches that seem to lie in the gray zone between being simply sketches and being a sort of Impressionism -- it's difficult to tell. But he largely continued on a traditional path after returning to America. There is no way of telling what he might have painted had he lived into the era of modernist "isms."
Painted when Bunker was about 19.
Another fairly elaborate sketch -- note that here and in the previous work he signed with only his initials.
Some French plein air type scenes.
This painting is also signed using initials.
A portrait reminiscent of Whistler's work.
A late work. I wrote about her here.