Brevity, not necessarily speed, is the way to capture the essence of your subject. You should come away from the subject feeling you have enough information to be able to make sense of it later.
Finished Painting, watercolour 5" x 7"
Drawing as a starting point
Capturing the essence of your subject has to be your main objective when time; weather (primarily the changing light), unwelcome observers (I have had sketchbooks plucked out of my hands while in china, so they could have a better look.) and patience is limited.
Working fairly quickly isn’t necessarily the answer, brevity is. Your role as an artist is to capture the image with as many, or as few, well placed lines as possible. To reduce the image in front of you to as much information as you need in order to either develop the work later by using your sketch as a starting point or as inspiration in a more considered piece/s back in the comfort of your studio.
The beauty of a sketch compared to that of a drawing (which may well be extremely well crafted and accurate), is the complete ease and lack of pretension exhibited, the ability to get to the nub of the matter and to ignore frippery and unwanted detail. It is this, which you want to be made aware of, when you go to develop that sketch.
What was it that originally attracted me to the subject? This is the question you should always ask yourself, as forgetting this, means the image loses its focus and power.
Mists on the grand canal
Fishmarket lantern. venice