Chiaroscuro

Chiaroscuro is a technique for producing bold contrasts of light and shade in pictorial representation to create depth and form. It means Chiaro (light) and scuro (dark) in Italian. From  its origins during the Renaissance many very well known artists over the centuries have used this technique to their advantage. Indeed for some it has become almost a trademark.
Leonardo Da Vinci pioneered chiaroscuro by establishing a monochrome underpainting using contrasting lights and darks. Then build up the painting with various coloured glazes. This can be seen clearly in Madonna (or Virgin) of the Rocks (1506) :
http://en.wikipedia.org/wiki/Virgin_of_the_Rocks#mediaviewer/File:Leonardo_da_Vinci_-_Virgin_of_the_Rocks_(Louvre).jpg
 Leonardo's style is often regarded as sfumato as opposed to typical chiaroscuro of later years, because the tonal transitions are more subtle.


Later artists used chiaroscuro  to more dramatic effect such as Caravaggio, Tintoretto, Rubens, Rembrandt and Joseph Wright of Derby. They  were some of its greatest proponents and all used it to dramatic effect. The main characteristics of their paintings are the iilusion of a spotlight illuminating the main focal areas, surrounded by often expansive heavy dark areas giving the impression of nightime. These scenes would in fact usually be lit by candlelight, fire or moonlight.

Carravagio's highly dramatic style became instrumental in developing tenebrism where extreme chiaroscuro dominates.

There is a sensation of a strong pull towards the face of Christ in this painting. Brightly illuminated faces, hands and the armour covering arm of a soldier are all turned in the direction of one person - Jesus, with the exception of the person on the far left who appears to be in a panic trying to get away. Especially noticeable though is the light edge of the armour.
The main source of light seems to be from the left although there's a lantern held by a man on the right. Heightening the sense of drama, as with so many of Carravagio's works, is the violent theme of the painting and the harsh contrasts.
http://en.wikipedia.org/wiki/The_Taking_of_Christ_(Caravaggio)#mediaviewer/File:Caravaggio_-_Taking_of_Christ_-_Dublin.jpg


Strongly influenced by Carravagio, Rubens also exploited extreme effects of light and shade, as can be seen in The Massacre of the Innocents:
http://en.wikipedia.org/wiki/Massacre_of_the_Innocents_(Rubens)#mediaviewer/File:Peter_Paul_Rubens_Massacre_of_the_Innocents.jpg      though the background is

less of a mystery.

In the second painting - Night Scene,:
http://upload.wikimedia.org/wikipedia/commons/7/7d/Peter_Paul_Rubens_-_Night_Scene_-_WGA20423.jpg
 although the strong contrasts are very evident the two faces and the hands again are the focus, they are more subtle than in Rubens first painting shown here and Carravaggio's - above. This of course is in keeping with  the gentle happy theme of an old woman with a young boy at her side who appears to be lighting a candle off hers. The right eye of each of them has a noticeable sparkle.

Rembrandt - being another great exponent of dramatic contrasts was fond of portraits placing brightly illuminated faces against dark sombre backgrounds. However, as in these two self portraits, the tonal transitions are more blurred along the edges than on Carravagio's paintings and the light is quite soft on the second portrait, echoing the gentle looking nature of the subject. His early works used a single light source so this self portrait as a young man is probably one of them, hence the reason for the blurred edges:

http://www.humanitiesweb.org/spa/gcp/ID/5218/c/538

I would guess that the second one is lit the same way:
http://en.wikipedia.org/wiki/Self-portrait_as_Zeuxis_Laughing


Joseph Wright of Derby was a painter of many subjects with a scientific theme,  containing large groups of people closely observing an experiment or studying a statue, all with strong chiaroscuro.

The two studies below show people viewing statues by candlelight. At the time candlelight used to illuminate statues in this way was commonly regarded as a good way of throwing on them a strange life.

In Academy by Lamplight the statue and the observer in bright focus appear to be transfixed by one another and. Between them are the small boy whose face looks up in wonderment and the man standing nearby with his head turned away to the left is looking rather nonchalant.

The centre of attention in the next painting is the small statue under intense observation by the three surrounding people. 

http://commons.wikimedia.org/wiki/File:Joseph_Wright_of_Derby_-_Academy_by_Lamplight_-_Google_Art_Project.jpg

http://www.topofart.com/artists/Wright-of-Derby/art-reproduction/4281/Three-Persons-Viewing-the-Gladiator-by-Candle-Light.php

The next image is a prison scene, giving a real sense of bleakness owing to the expanses of extreme darkness around the outer perimeter, framing a corridor like structure leading to a small glowing window suggesting 'light at the end of the tunnel' - hopefully.
http://commons.wikimedia.org/wiki/File:Joseph_Wright_of_Derby._Small_Prison_Scene._c.1787-90..jpg

I noticed when searching online through some of his other paintings, that he was also a prolific painter of volcanic eruptions, which of course would have been in keeping with his dramatic use of tonal contrasts.

What is common to many of the paintings above are  the mysterious dark backgrounds and the strong tonal contrasts bringing the brightly lit figures into dramatically strong focus.