This was painted in the studio, which means I painted from reference. Reference could be studies or photo's. For me it is ALWAYS my photo and my study. Below is something I put together as an answer to a question I am often asked.
WHAT IS "PLEIN AIR?”
The term "plein-air" comes from the French phrase en plein-air which is an idiom that does not translate directly, but simply means "outdoors." Similarly, in Italian, the phrase is al fresco, and in Spanish it's al aire libre.
Plein air painting is a specialized approach that landscape painters have utilized for more than one hundred and fifty years. Plein air is not a philosophy, nor a style, and it is not a static state that one reaches and remains in perpetual happiness. It is unquestionably a landscape painter's most effective tool. When followed to its completion, the plein air technique has proven over and over that it is the best approach to paint natural light.
Perhaps like no other artist, the plein air painter is mesmerized by natural light. The passion for light drives them to seek the genuine experience and paint it, regardless of climate, weather or natural impediments. Hence, it is as a plein-air painter that the landscape painter finds the ultimate reason for being, and at the same time, confronts their most rigorous challenge: to capture quickly the brilliant and fluid visual sensation of natural light at a specific time and place while facing the formidable constraint of fleeting natural light.
The most important point of plein air painting is that it is not the end product, it is in fact, the beginning. It is how one starts the process of creating a successful landscape painting.