Luminism - What is?

Leander's Tower on the Bosphorus (1876)

What is Luminism?

From Wiki Luminism is an American landscape painting style of the 1850s to 1870s, characterized by the effects of light in landscape, through the use of aerial perspective and the concealment of visible brushstrokes. Luminist landscapes emphasize tranquility and often depict calm, reflective water and a soft, hazy sky. Artists who were most central to the development of the luminist style include Fitz Hugh Lane, Martin Johnson, Johnson Heade and Sanford Gifford.

one of my favourites is this one of the Bosphorus, it uses light and colour and seems to have innate luminosity! Now if only I could paint like that! There is so much detail only using what appears to be one colour but which could be made up from several.

These are a few examples of luminism.

Ruins of the  Panthenon 1880

Lake Geneve 1875

Venetian Sails, A Study (1873)

Mr. Gifford's method is this: When he sees anything which vividly impresses him, and which therefore he wishes to reproduce, he makes a little sketch of it in pencil on a card about as large as an ordinary visiting-card. It takes him, say, half a minute to make it; there is the idea of the future picture fixed as firmly if not as fully as the completed work itself. While traveling, he can in this way lay up a good stock of material for future use. The next step is to make a larger sketch, this time in oil, where what has already been done in black-and-white is repeated in color. To this sketch, which is about twelve inches by eight, he devotes an hour or two. It serves the purpose of defining to him just what he wants to do. He experiments with it; puts in or leaves out, according as he finds that he can increase or perfect his idea. When satisfactorily finished, it is a model of what he proposes to do.
He is now ready to paint the picture itself. When the day comes, he begins work just after sunrise, and continues until just before sunset. Ten, eleven, twelve consecutive hours, according to the season of the year, are occupied in the first great effort to put the scene on canvas. He feels fresh and eager. His studio-door is locked. Nothing is allowed to interrupt him.
When the long day is finished and the picture is produced, the work of criticism, of correction, of completion, is in place. Mr. Gifford does this work slowly. He likes to keep his picture in his studio as long as possible. Sometimes he does not touch the canvas for months after his first criticisms have been executed. Then, suddenly, he sees something that will help it along. 

How many of us sketch to keep the eye of what we see and so we can later on use that sketch and our eye will remember and make it easier to paint?