Diego Velazquez' painting is named Las Meninas, literally "The Maids of Honor" in Spanish, but the center of the painting is still the Infanta, Margaret Theresa, the daughter of the King and Queen of Spain. By showing the Infanta's retinue, including the maids of honor, a chaperone, dwarves, and pets, as well as himself painting the work, Velazquez presents the reality of the royal household in a critical, if non-judgmental, manner.  Adding to this effect is the presentation of the King and Queen in a mirror at the back of the room, putting the viewer in the position of the royal couple.

Image is in the public domain, accessed through Wikipedia Media Commons: https://commons.wikimedia.org/wiki/File:Las_Meninas,_by_Diego_Velázquez,_from_Prado_in_Google_Earth.jpg

Las Meninas is, essentially, a portrait of the royal household, especially the retinue of people surrounding the Infanta Margaret Theresa. In the middle of this portrait Diego Velazquez has included an image of himself painting the scene. Velazquez official position was as the court painter to Philip IV, King of Spain, which meant he lived and worked in the Alcazar, the royal palace of the Spanish Monarchs.

Image is in the public domain, accessed through Wikipedia Media Commons: https://commons.wikimedia.org/wiki/File:Las_Meninas,_by_Diego_Velázquez,_from_Prado_in_Google_Earth.jpg

The style in which Wright painted A Philosopher Giving a Lecture on the Orrery was normally reserved for "history painting." These paintings would often be scenes with historical or religious figures, or of mythological heroes, and usually had a moral implication. Wright chose to paint a scientific scene in this way, which emphasized the importance of the Enlightenment at the time.

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The positioning of each adult in the photo is meant to represent the phases of the moon -- new moon, half moon, gibbous moon and full moon. Wright demonstrates this by his dramatic use of light and shadow. The shadows on their faces illustrate what the moon looks like when it rotates around the sun.

Image is in the public domain, accessed through Wikipedia Media Commons: https://en.wikipedia.org/wiki/File:Wright_of_Derby,_The_Orrery.jpg

A Philosopher Giving a Lecture on the Orrery is painted with various intended references -- it does resemble a conversation piece portrait, and many of the figures are based on real life groups and people (specifically, the Lunar Society and Sir Isaac Newton). It is also one in a series of "candlelight paintings" that Wright created that made use of tenebrism and emphasized scientific topics. This work, however, was painted in the 18th century.  The Renaissance period took place between the 14th and 17th centuries in Europe.

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Neoclassicism was an artistic movement developed in the late eighteenth century that greatly valued classical ideals in art, particularly in crafting highly structured compositions which fit very specific guidelines. Among these guidelines were a de-emphasized background, use of a central vanishing point that focused the painting on one spot, frequent use of overlapping figures in profile, stoic expressions on main figures, and a heavy reliance on straight lines. Among the key stylistic elements of Neoclassical was a desire to hide any and all brushstrokes, so as to make sure the viewer was not distracted from understanding the painting's message by the artist's physical work.

Artwork from Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Jacques-Louis_David,_Le_Serment_des_Horaces.jpg

Both the philosophical movement called the Enlightenment and the artistic movement Neoclassicism, of which The Oath of the Horatii is representative, were both developed in France during the eighteenth century. Beyond geographical proximity, each movement also looked to Ancient Rome and Greece for inspiration, highly prized rationality over emotionalism, and favored strict order and logic. 

Artwork from Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Jacques-Louis_David,_Le_Serment_des_Horaces.jpg

French for "deceive the eye," trompe l'oeil is the painting technique where the artist makes an image that appears three dimensional and outside the painting. The concept goes back to Roman art, where walls in houses would have fake windows of iterms painted on, but was first defined in the Baroque era. The technique can be used to either enhance the dimensionality of a painting, or as a kind of artistic joke, featuring a "mistaken" element.

Each painting features a remarkable realism in its portrayal of the figures included therein, including a self portrait of the painter. Francisco de Goya likely included himself in his painting as a nod to Velázquez' own self-portrait in Las Meninas, with both standing behind an easel placed in the left side of the painting. Both painters include themselves to make the viewer rethink what they see in the painting of royalty, with the gaze of the painter staring back at the viewer.

Figure 1: Las Meninas by Diego Velázquez (1656)

Figure 2: Charles IV of Spain and His Family Francisco de Goya (1801)

Chiaroscuro is an artistic term denoting a strong contrast between dark and light elements. First developed and defined in Italy in the late sixteenth century, chiaroscuro was a key element of Rembrandt van Rijn's style. In The Night Watch, he throws significant light on the group's leaders exiting the hall, with shadow taking over those in the back.

Figure 3: The Night Watch by Rembrandt van Rijn (1642)

Figure 4: The Astronomer by Johannes Vermeer (1668)