Question: What are the foreground figures done in?
About the article "Donatello", section "Work in Florence".

Candidate passages:
The Doni Tondo is believed to be the only existing panel picture Michelangelo painted without the aid of assistants; and, unlike his Manchester Madonna and "Entombment" (both National Gallery, London) the attribution to him has never been questioned.
The juxtaposition of bright colors foreshadows the same use of color in Michelangelo’s later Sistine ceiling frescoes.
The folds of the drapery are sharply modeled, and the skin of the figures is so smooth, it looks as if the medium is marble.
The surface treatment of the massive figures resembles a sculpture more than a painting.
The nude figures in the background have softer modeling and look to be precursors to the "ignudi", the male nude figures in the Sistine Ceiling frescoes.
Michelangelo’s technique includes shading from the most intense colors first to the lighter shades on top, using the darker colors as shadows, a technique called "cangiante".
By applying the pigment in a certain way, Michelangelo created an ""unfocused"" effect in the background and focused detail in the foreground.
The most vibrant color is located within the Virgin’s garments, which signifies her importance within the image.
X-rays of the painting show that Michelangelo incorporated every known pigment used at the time.
The masculinity of Mary could be explained by Michelangelo’s use of male models for female figures, as was done for the Sistine Chapel. 
His works often depict groups of figures, the principal subject always clearly located in the foreground.
He uses bright colors, especially for clothing.
In Knoller's work, individuals are dominant.
He has a less rigid approach to classicism, the colours are less powerful while the composition is clear and well-ordered, free of Baroque pathos.
A master of perspective, he depicts his figures in unusual attitudes. 
Example: "Das Kunstgespräch" (The Art Discussion).
This important work of 1777 shows, in the foreground on the right, the Saxon statesman, Thomas Fritsch (1700-1775), together with Christian Ludwig von Hagedorn, art theorist and collector.
Both are engrossed in a conversation about art.
On the table between them, allegorical figures representing painting, sculpture and poetry can be seen.
Amongst those listening in the background are painters Adrian Zingg (left), Schenau himself and Anton Graff. 
Passive voice is a grammatical voice common in many of the world's languages.
In a clause with passive voice, the grammatical subject expresses the "theme" or "patient" of the main verb – that is, the person or thing that undergoes the action or has its state changed.
This contrasts with active voice, in which the subject has the agent role.
For example, in the passive sentence "The tree was pulled down", the subject ("the tree") denotes the patient rather than the agent of the action.
In contrast, the sentences "Someone pulled down the tree" and "The tree is down" are active sentences.
Typically, in passive clauses, what would otherwise be expressed by the object (or sometimes another argument) of the verb comes to be expressed by the subject, while what would otherwise be expressed by the subject is either not expressed at all, or is indicated by some adjunct of the clause.
Thus transforming an active verb into a passive verb is a valence-decreasing process ("detransitivizing process"), because it transforms transitive verbs into intransitive verbs.
This is not always the case; for example in Japanese a passive-voice construction does not necessarily decrease valence.
Many languages have both an active and a passive voice; this allows for greater flexibility in sentence construction, as either the semantic agent or patient may take the syntactic role of subject.
The use of passive voice allows speakers to organize stretches of discourse by placing figures other than the agent in subject position.
This may be done to foreground the patient, recipient, or other thematic role; it may also be useful when the semantic patient is the topic of on-going discussion.
The passive voice may also be used to avoid specifying the agent of an action. 
Background subtraction, also known as Foreground Detection, is a technique in the fields of image processing and computer vision wherein an image's foreground is extracted for further processing (object recognition etc.).
Generally an image's regions of interest are objects (humans, cars, text etc.)
in its foreground.
After the stage of image preprocessing (which may include image denoising etc.)
object localisation is required which may make use of this technique.
Background subtraction is a widely used approach for detecting moving objects in videos from static cameras.
The rationale in the approach is that of detecting the moving objects from the difference between the current frame and a reference frame, often called “background image”, or “background model”.
Background subtraction is mostly done if the image in question is a part of a video stream.