Franz Hals was a Dutch portrait painter who reflected the Dutch interest of secular, non-religious images in his artwork; he did not paint saints or biblical figures. These portraits of "common people" and peasants became more common until the time of the American and French Revolution. In his portrait paintings he added interest and emotion along with lifelike detail to make the image of an individual look as much like a candid photo as possible. He used quick, dashing brush strokes to give his works a fresh, just-finished look. His illusion is to catch an instantaneous expression of character. His famous work of the Young Man and Woman in an Inn, painted in 1623, beautifully expresses this. This dashing portrait here is called The Laughing Cavalier, painted in 1624.
This is fun to examine more closely as an optical illusion as well as simply a great painting. The title can be deceptive. Is the man really laughing or even smiling? The ambitious moustache above his lips causes our eye to transfer the curvature of the line to the bottom lip, but if you have a thin pencil, cover the moustache, and look at the painting again you may see a different expression on his face than a smile. But the cheekbones also have to be taken into account. The way my teacher described her impression of it was that it is capturing the moment right before someone bursts into a smile or a laugh—you know that nasal noise one makes under a restrained giggle that precedes an open smile. Hals' paintings often deal with specific human emotions and expressions like that; his interest is in people, everyday common people, not saints or religious figures. This is the Protestant perspective.
Judith Leyster was also a famous Dutch portrait painter at the time. Here is a Self-Portrait of her from 1635.
When Louvre officials cleaned a painting thought to be done by Franz Hals, they found the signature of Judith Leyster. The misconception owes itself to the fact that Leyster's paintings are very similar to Hals'; in fact, she was friends with the artist. She studied the techniques of many artists and allowed their styles to impact her own. She implemented Caravaggio's dramatic use of light and dark. She obviously took inspiration from Hals' portrait of human emotions and expressions as can be seen in such paintings as this famous one by her of the Young Flute Player.