Stephen Prince – författare
Visar alla böcker från författaren Stephen Prince. Handla med fri frakt och snabb leverans.
35 produkter
35 produkter
Häftad, Engelska, 2012
3 126 kr
Skickas inom 3-6 vardagar
Updated in a new 6th edition, Movies and Meaning is a comprehensive introduction to the film industry that focuses on three topics: how movies express meanings, how viewers understand those meanings, and how cinema functions globally as both an art and a business. It examines both how filmmakers create images and sounds and the mechanisms and processes by which viewers make sense of images and stories on screen.
Inbunden, Engelska, 2009
1 334 kr
Skickas inom 5-8 vardagar
It was believed that September 11th would make certain kinds of films obsolete, such as action thrillers crackling with explosions or high-casualty blockbusters where the hero escapes unscathed. While the production of these films did ebb, the full impact of the attacks on Hollywood's creative output is still taking shape. Did 9/11 force filmmakers and screenwriters to find new methods of storytelling? What kinds of movies have been made in response to 9/11, and are they factual? Is it even possible to practice poetic license with such a devastating, broadly felt tragedy? Stephen Prince is the first scholar to trace the effect of 9/11 on the making of American film. From documentaries like Fahrenheit 9/11 (2004) to zombie flicks, and from fictional narratives such as The Kingdom (2007) to Mike Nichols's Charlie Wilson's War (2007), Prince evaluates the extent to which filmmakers have exploited, explained, understood, or interpreted the attacks and the Iraq War that followed, including incidents at Abu Ghraib. He begins with pre-9/11 depictions of terrorism, such as Alfred Hitchcock's Sabotage (1936), and follows with studio and independent films that directly respond to 9/11.He considers documentary portraits and conspiracy films, as well as serial television shows (most notably Fox's 24) and made-for-TV movies that re-present the attacks in a broader, more intimate way. Ultimately Prince finds that in these triumphs and failures an exciting new era of American filmmaking has taken shape.
Häftad, Engelska, 2009
339 kr
Skickas inom 5-8 vardagar
It was believed that September 11th would make certain kinds of films obsolete, such as action thrillers crackling with explosions or high-casualty blockbusters where the hero escapes unscathed. While the production of these films did ebb, the full impact of the attacks on Hollywood's creative output is still taking shape. Did 9/11 force filmmakers and screenwriters to find new methods of storytelling? What kinds of movies have been made in response to 9/11, and are they factual? Is it even possible to practice poetic license with such a devastating, broadly felt tragedy? Stephen Prince is the first scholar to trace the effect of 9/11 on the making of American film. From documentaries like Fahrenheit 9/11 (2004) to zombie flicks, and from fictional narratives such as The Kingdom (2007) to Mike Nichols's Charlie Wilson's War (2007), Prince evaluates the extent to which filmmakers have exploited, explained, understood, or interpreted the attacks and the Iraq War that followed, including incidents at Abu Ghraib. He begins with pre-9/11 depictions of terrorism, such as Alfred Hitchcock's Sabotage (1936), and follows with studio and independent films that directly respond to 9/11.He considers documentary portraits and conspiracy films, as well as serial television shows (most notably Fox's 24) and made-for-TV movies that re-present the attacks in a broader, more intimate way. Ultimately Prince finds that in these triumphs and failures an exciting new era of American filmmaking has taken shape.
E-bok
Engelska, 2009515 kr
Läs direkt efter köp
It was believed that September 11th would make certain kinds of films obsolete, such as action thrillers crackling with explosions or high-casualty blockbusters where the hero escapes unscathed. While the production of these films did ebb, the full impact of the attacks on Hollywood's creative output is still taking shape. Did 9/11 force filmmakers and screenwriters to find new methods of storytelling? What kinds of movies have been made in response to 9/11, and are they factual? Is it even possible to practice poetic license with such a devastating, broadly felt tragedy?Stephen Prince is the first scholar to trace the effect of 9/11 on the making of American film. From documentaries like Fahrenheit 9/11 (2004) to zombie flicks, and from fictional narratives such as The Kingdom (2007) to Mike Nichols's Charlie Wilson's War (2007), Prince evaluates the extent to which filmmakers have exploited, explained, understood, or interpreted the attacks and the Iraq War that followed, including incidents at Abu Ghraib. He begins with pre-9/11 depictions of terrorism, such as Alfred Hitchcock's Sabotage (1936), and follows with studio and independent films that directly respond to 9/11. He considers documentary portraits and conspiracy films, as well as serial television shows (most notably Fox's 24) and made-for-TV movies that re-present the attacks in a broader, more intimate way. Ultimately Prince finds that in these triumphs and failures an exciting new era of American filmmaking has taken shape.
Inbunden, Engelska, 1992
1 050 kr
Skickas inom 10-15 vardagar
Visions of Empire explores film's function as a medium of political communication, recognizing not just the propaganda film, but the various ways that conventional narrative films embody, question, or critique established social values underlying American attitudes toward historical, social, and political events. Stephen Prince discusses Hollywood film productions of the 1980s in terms of salient political issues of the period, including anxieties about declining U.S. military power, the wars in Central America and the prospects for U.S. intervention, the legacy of the Vietnam War, and urban decay. In analyzing these images and narratives, the author also describes and evaluates the cinematic styles available in the Hollywood tradition to filmmakers who address political issues.Chapter 1 establishes the theoretical framework by considering features of the political landscape of the Reagan era. Theories about political representation and the place of ideology in film are also examined. Chapters 2 through 5 focus on the major cycles of political films. Chapter 2 examines the new Cold War films which played upon fears of the Soviet menace (Rambo, Invasion USA, Red Dawn, and Top Gun). Chapter 3 discusses the small group of films--Under Fire, Salvador, El Norte and others--that addressed the wars in Latin America and the ways they explained the origins of the conflicts and the U.S. role therein. Various histories and mythologies on film of the Vietnam War are examined in Chapter 4 as examples of the symbolic reconstruction of social memory. Chapter 5 looks at politicized science fiction films (Blade Runner, Aliens, Robocop, and Total Recall) offering critical commentaries on the pathologies of contemporary urban society and capitalism.
Häftad, Engelska, 1992
539 kr
Skickas inom 10-15 vardagar
Visions of Empire explores film's function as a medium of political communication, recognizing not just the propaganda film, but the various ways that conventional narrative films embody, question, or critique established social values underlying American attitudes toward historical, social, and political events. Stephen Prince discusses Hollywood film productions of the 1980s in terms of salient political issues of the period, including anxieties about declining U.S. military power, the wars in Central America and the prospects for U.S. intervention, the legacy of the Vietnam War, and urban decay. In analyzing these images and narratives, the author also describes and evaluates the cinematic styles available in the Hollywood tradition to filmmakers who address political issues.Chapter 1 establishes the theoretical framework by considering features of the political landscape of the Reagan era. Theories about political representation and the place of ideology in film are also examined. Chapters 2 through 5 focus on the major cycles of political films. Chapter 2 examines the new Cold War films which played upon fears of the Soviet menace (Rambo, Invasion USA, Red Dawn, and Top Gun). Chapter 3 discusses the small group of films--Under Fire, Salvador, El Norte and others--that addressed the wars in Latin America and the ways they explained the origins of the conflicts and the U.S. role therein. Various histories and mythologies on film of the Vietnam War are examined in Chapter 4 as examples of the symbolic reconstruction of social memory. Chapter 5 looks at politicized science fiction films (Blade Runner, Aliens, Robocop, and Total Recall) offering critical commentaries on the pathologies of contemporary urban society and capitalism.
Häftad, Engelska, 1998
346 kr
Skickas inom 10-15 vardagar
More than any other filmmaker, Sam Peckinpah opened the door for graphic violence in movies. In this book, Stephen Prince explains the rise of explicit violence in the American cinema, its social effects, and the relation of contemporary ultraviolence to the radical, humanistic filmmaking that Peckinpah practiced. Prince demonstrates Peckinpah's complex approach to screen violence and shows him as a serious artist whose work was tied to the social and political upheavals of the 1960s. He explains how the director's commitment to showing the horror and pain of violence compelled him to use a complex style that aimed to control the viewer's response. Prince offers an unprecedented portrait of Peckinpah the filmmaker. Drawing on primary research materials-Peckinpah's unpublished correspondence, scripts, production memos, and editing notes-he provides a wealth of new information about the making of the films and Peckinpah's critical shaping of their content and violent imagery. This material shows Peckinpah as a filmmaker of intelligence, a keen observer of American society, and a tragic artist disturbed by the images he created. Prince's account establishes, for the first time, Peckinpah's place as a major filmmaker. This book is essential reading for those interested in Peckinpah, the problem of movie violence, and contemporary American cinema.
E-bok
PDF, Engelska, 1992578 kr
Läs direkt efter köp
Visions of Empire explores film's function as a medium of political communication, recognizing not just the propaganda film, but the various ways that conventional narrative films embody, question, or critique established social values underlying American attitudes toward historical, social, and political events. Stephen Prince discusses Hollywood film productions of the 1980s in terms of salient political issues of the period, including anxieties about declining U.S. military power, the wars in Central America and the prospects for U.S. intervention, the legacy of the Vietnam War, and urban decay. In analyzing these images and narratives, the author also describes and evaluates the cinematic styles available in the Hollywood tradition to filmmakers who address political issues.Chapter 1 establishes the theoretical framework by considering features of the political landscape of the Reagan era. Theories about political representation and the place of ideology in film are also examined. Chapters 2 through 5 focus on the major cycles of political films. Chapter 2 examines the new Cold War films which played upon fears of the Soviet menace (Rambo, Invasion USA, Red Dawn, and Top Gun). Chapter 3 discusses the small group of films--Under Fire, Salvador, El Norte and others--that addressed the wars in Latin America and the ways they explained the origins of the conflicts and the U.S. role therein. Various histories and mythologies on film of the Vietnam War are examined in Chapter 4 as examples of the symbolic reconstruction of social memory. Chapter 5 looks at politicized science fiction films (Blade Runner, Aliens, Robocop, and Total Recall) offering critical commentaries on the pathologies of contemporary urban society and capitalism.
Häftad, Engelska, 2013
556 kr
Skickas inom 5-8 vardagar
An Introduction to Film Genres, written by leading film scholars specifically for undergraduates who are new to the study of film, provides an introduction that helps students see thirteen film genres in a new light---to help them identify the themes, iconography, and distinctive stylistic traits of each genre.
Häftad, Engelska, 2000
1 398 kr
Skickas inom 10-15 vardagar
Following the release in 1967 of "Bonnie and Clyde" and "The Dirty Dozen", violence has been seen as a defining feature of the modern film. Is it art or exploitation? Danger or liberation? This volume provides an exmination of the history and effects of graphic violence on film.
Del 10 - History of the American Cinema
New Pot of Gold
Hollywood under the Electronic Rainbow, 1980–1989
Häftad, Engelska, 2002
391 kr
Skickas inom 5-8 vardagar
Facing an economic crisis in the 1980s, the Hollywood industry moved boldly to control the ancillary markets of videotape, video disk, pay-cable and pay-per-view, and the major studios found themselves targeted for acquisition by global media and communications companies. This volume examines the decade's transformation that took Hollywood from the production of theatrical film to media software. Some of the films discussed in this volume include: "Platoon"; "Do the Right Thing"; "Blue Velvet"; "Diner"; "E.T."; "Batman"; and, "Body Heat".
Häftad, Engelska, 1998
240 kr
Skickas inom 7-10 vardagar
Sam Peckinpah's The Wild Bunch is one of the most influential films in American cinema. The intensity of its violence was unprecedented, while the director's use of multiple cameras, montage editing, and slow motion quickly became the normative style for rendering screen violence. Demonstrating to filmmakers the power of irony as a narrative voice and its effectiveness as a tool for exploring and portraying brutality, The Wild Bunch fundamentally changed the Western, moving it into a more brutal and psychopathic territory than it had ever occupied. This volume includes newly commissioned essays by several leading scholars of Peckinpah's work. Examining the film's production history from script to screen, its rich and ambivalent vision of American society, and its relationship to the Western genre, among other topics, it provides a definitive reinterpretation of an enduring film classic.
Häftad, Engelska, 1999
545 kr
Skickas inom 5-8 vardagar
The Japanese film director Akira Kurosawa, who died at the age of 88, has been internationally acclaimed as a giant of world cinema. Rashomon, which won both the Venice Film Festival's grand prize and an Academy Award for best foreign-language film, helped ignite Western interest in the Japanese cinema. Seven Samurai and Yojimbo remain enormously popular both in Japan and abroad. In this newly revised and expanded edition of his study of Kurosawa's films, Stephen Prince provides two new chapters that examine Kurosawa's remaining films, placing him in the context of cinema history. Prince also discusses how Kurosawa furnished a template for some well-known Hollywood directors, including Martin Scorsese, Steven Spielberg, and George Lucas. Providing a new and comprehensive look at this master filmmaker, The Warrior's Camera probes the complex visual structure of Kurosawa's work. The book shows how Kurosawa attempted to symbolize on film a course of national development for post-war Japan, and it traces the ways that he tied his social visions to a dynamic system of visual and narrative forms.The author analyzes Kurosawa's entire career and places the films in context by drawing on the director's autobiography--a fascinating work that presents Kurosawa as a Kurosawa character and the story of his life as the kind of spiritual odyssey witnessed so often in his films. After examining the development of Kurosawa's visual style in his early work, The Warrior's Camera explains how he used this style in subsequent films to forge a politically committed model of filmmaking. It then demonstrates how the collapse of Kurosawa's efforts to participate as a filmmaker in the tasks of social reconstruction led to the very different cinematic style evident in his most recent films, works of pessimism that view the world as resistant to change.
E-bok
Engelska, 2020681 kr
Läs direkt efter köp
The Japanese film director Akira Kurosawa, who died at the age of 88, has been internationally acclaimed as a giant of world cinema. Rashomon, which won both the Venice Film Festival''s grand prize and an Academy Award for best foreign-language film, helped ignite Western interest in the Japanese cinema. Seven Samurai and Yojimbo remain enormously popular both in Japan and abroad. In this newly revised and expanded edition of his study of Kurosawa''s films, Stephen Prince provides two new chapters that examine Kurosawa''s remaining films, placing him in the context of cinema history. Prince also discusses how Kurosawa furnished a template for some well-known Hollywood directors, including Martin Scorsese, Steven Spielberg, and George Lucas. Providing a new and comprehensive look at this master filmmaker, The Warrior''s Camera probes the complex visual structure of Kurosawa''s work. The book shows how Kurosawa attempted to symbolize on film a course of national development for post-war Japan, and it traces the ways that he tied his social visions to a dynamic system of visual and narrative forms. The author analyzes Kurosawa''s entire career and places the films in context by drawing on the director''s autobiography--a fascinating work that presents Kurosawa as a Kurosawa character and the story of his life as the kind of spiritual odyssey witnessed so often in his films. After examining the development of Kurosawa''s visual style in his early work, The Warrior''s Camera explains how he used this style in subsequent films to forge a politically committed model of filmmaking. It then demonstrates how the collapse of Kurosawa''s efforts to participate as a filmmaker in the tasks of social reconstruction led to the very different cinematic style evident in his most recent films, works of pessimism that view the world as resistant to change.
Häftad, Engelska, 2000
424 kr
Skickas inom 10-15 vardagar
Graphic cinematic violence is a magnet for controversy. From passionate defenses to outraged protests, theories abound concerning this defining feature of modern film: Is it art or exploitation, dangerous or liberating? Screening Violence provides an even-handed examination of the history, merits, and effects of cinematic “ultraviolence.” Movie reviewers, cinematographers, film scholars, psychologists, and sociologists all contribute essays exploring topics such as:· the origins and innovations of film violence and attempts to regulate it (from Hollywood’s Production Code to the evolution of the ratings system)· the explosion of screen violence following the 1967 releases of Bonnie and Clyde and The Dirty Dozen, and the lasting effects of those landmark films· the aesthetics of increasingly graphic screen violence· the implications of our growing desensitization to murder and mayhem, from The Wild Bunch to The Terminator
Häftad, Engelska, 2004
401 kr
Skickas inom 5-8 vardagar
In this volume, Stephen Prince has collected essays reviewing the history of the horror film and the psychological reasons for its persistent appeal, as well as discussions of the developmental responses of young adult viewers and children to the genre. The book focuses on recent postmodern examples such as The Blair Witch Project. In a daring move, the volume also examines Holocaust films in relation to horror. Part One features essays on the silent and classical Hollywood eras. Part Two covers the postWorld War II era and discusses the historical, aesthetic, and psychological characteristics of contemporary horror films. In contrast to horror during the classical Hollywood period, contemporary horror features more graphic and prolonged visualizations of disturbing and horrific imagery, as well as other distinguishing characteristics. Princes introduction provides an overview of the genre, contextualizing the readings that follow.Stephen Prince is professor of communications at Virginia Tech. He has written many film books, including Classical Film Violence: Designing and Regulating Brutality in Hollywood Cinema, 19301968, and has edited Screening Violence, also in the Depth of Field Series.
Häftad, Engelska, 2007
688 kr
Skickas inom 3-6 vardagar
Häftad, Engelska, 2012
446 kr
Skickas inom 5-8 vardagar
Avatar. Inception. Jurassic Park. Lord of the Rings. Ratatouille. Not only are these some of the highest-grossing films of all time, they are also prime examples of how digital visual effects have transformed Hollywood filmmaking. Some critics, however, fear that this digital revolution marks a radical break with cinematic tradition, heralding the death of serious realistic movies in favor of computer-generated pure spectacle.Digital Visual Effects in Cinema counters this alarmist reading, by showing how digital effects–driven films should be understood as a continuation of the narrative and stylistic traditions that have defined American cinema for decades. Stephen Prince argues for an understanding of digital technologies as an expanded toolbox, available to enhance both realist films and cinematic fantasies. He offers a detailed exploration of each of these tools, from lighting technologies to image capture to stereoscopic 3D. Integrating aesthetic, historical, and theoretical analyses of digital visual effects, Digital Visual Effects in Cinema is an essential guide for understanding movie-making today.
Inbunden, Engelska, 2017
595 kr
Skickas inom 11-20 vardagar
Celebrated as one of Japan's greatest filmmakers, Kobayashi Masaki's scorching depictions of war and militarism marked him as a uniquely defiant voice in post-war Japanese cinema. A pacifist drafted into Japan's Imperial Army, Kobayashi survived the war with his principles intact and created a body of work that was uncompromising in its critique of the nation's military heritage. Yet his renowned political critiques were grounded in spiritual perspectives, integrating motifs and beliefs from both Buddhism and Christianity. A Dream of Resistance is the first book in English to explore Kobayashi's entire career, from the early films he made at Shochiku studio, to internationally-acclaimed masterpieces like The Human Condition, Harakiri, and Samurai Rebellion, and on to his final work for NHK Television. Closely examining how Kobayashi's upbringing and intellectual history shaped the values of his work, Stephen Prince illuminates the political and religious dimensions of Kobayashi's films, interpreting them as a prayer for peace in troubled times. Prince draws from a wealth of rare archives, including previously untranslated interviews, material that Kobayashi wrote about his films, and even the young director's wartime diary. The result is an unprecedented portrait of this singular filmmaker.
Häftad, Engelska, 2019
267 kr
Skickas inom 5-8 vardagar
Digital Cinema considers how new technologies have revolutionized the medium, while investigating the continuities that might remain from filmmaking’s analog era. In the process, it raises provocative questions about the status of realism in a pixel-generated digital medium whose scenes often defy the laws of physics. It also considers what these changes might bode for the future of cinema. How will digital works be preserved and shared? And will the emergence of virtual reality finally consign cinema to obsolescence? Stephen Prince offers a clear, concise account of how digital cinema both extends longstanding traditions of filmmaking and challenges some fundamental assumptions about film. It is essential reading for anyone interested in understanding how movies are shot, produced, distributed, and consumed in the twenty-first century.
Inbunden, Engelska, 2019
802 kr
Skickas inom 5-8 vardagar
Digital Cinema considers how new technologies have revolutionized the medium, while investigating the continuities that might remain from filmmaking’s analog era. In the process, it raises provocative questions about the status of realism in a pixel-generated digital medium whose scenes often defy the laws of physics. It also considers what these changes might bode for the future of cinema. How will digital works be preserved and shared? And will the emergence of virtual reality finally consign cinema to obsolescence? Stephen Prince offers a clear, concise account of how digital cinema both extends longstanding traditions of filmmaking and challenges some fundamental assumptions about film. It is essential reading for anyone interested in understanding how movies are shot, produced, distributed, and consumed in the twenty-first century.
Häftad, Engelska, 2013
1 030 kr
Skickas inom 7-10 vardagar
This comprehensive introduction to film text focuses on three topics: how movies express meanings, how viewers understand those meanings, and how cinema functions globally as both an art and a business. Using clear, accessible, and jargon-free writing, this is the only introductory film text to examine the elements of film style and the viewer's contribution to the cinema experience. How do viewers interpret the effects filmmakers create? How do filmmakers anticipate, and build on, the likely ways viewers will react to certain kinds of stories and audio-visual designs? The text examines both how filmmakers create images and sounds and the mechanisms and processes by which viewers make sense of images and stories on screen. This approach helps students understand not only the basic concepts but also how their own reactions and opinions impact the overall film experience.
Del 7 - Raid
Blocking of Zeebrugge
Operation Z-O 1918
E-bok
Engelska, 2012222 kr
Läs direkt efter köp
On the night of 22–23 April 1918 the Royal Navy carried out a raid on the German held ports of Zeebrugge and Ostend – Operation Z-O. Under the cover of clouds and smoke, over 70 ships and an assault force of 1,800 Royal Marines embarked on a daring mission which involved a vicious battle of incredible intensity. However, despite the gallant and courageous efforts of the attackers, 11 of whom were later awarded the Victoria Cross, the raid was only partly successful. Discover the successes and failures of this dramatic raid in this in-depth account, complete with specially commissioned battlescene artwork. The author reveals how despite failure, the raid demonstrated to Germany that Britain was still capable of offensive action, even as its armies were being forced back.
Häftad, Engelska, 2007
376 kr
Skickas inom 10-15 vardagar
During the 1980s, American cinema underwent enormous transformations. Blockbusters like Raiders of the Lost Ark, E.T., and The Empire Strikes Back earned huge sums for the studios. At the same time, the growth of home video led to new opportunities for independent film production, resulting in many of the decade's best films.Filmmakers responded to the social, political, and cultural conditions of the time, notably the Reagan presidency and the rebirth of the Cold War, which Hollywood films both embraced and critiqued. Hollywood also launched a long-awaited cycle of films about the Vietnam War, exploring its impact both at home and abroad. But science fiction remained the era's most popular genre, ranging from upbeat fantasies to dark, dystopic visions.American Cinema of the 1980s examines the films that marked the decade, including Ordinary People, Body Heat, Blade Runner, Zelig, Platoon, Top Gun, Aliens, Blue Velvet, Robocop, Fatal Attraction, Die Hard, Batman, and sex, lies & videotape.
Del 7 - Raid
Blocking of Zeebrugge
Operation Z-O 1918
Häftad, Engelska, 2010
194 kr
Skickas inom 10-15 vardagar
On the night of 22–23 April 1918 the Royal Navy carried out a raid on the German held ports of Zeebrugge and Ostend – Operation Z-O.Under the cover of clouds and smoke, over 70 ships and an assault force of 1,800 Royal Marines embarked on a daring mission which involved a vicious battle of incredible intensity. However, despite the gallant and courageous efforts of the attackers, 11 of whom were later awarded the Victoria Cross, the raid was only partly successful. Discover the successes and failures of this dramatic raid in this in-depth account, complete with specially commissioned battlescene artwork.The author reveals how despite failure, the raid demonstrated to Germany that Britain was still capable of offensive action, even as its armies were being forced back.
Del 7 - Raid
Blocking of Zeebrugge
Operation Z-O 1918
E-bok
PDF, Engelska, 2012222 kr
Läs direkt efter köp
On the night of 22–23 April 1918 the Royal Navy carried out a raid on the German held ports of Zeebrugge and Ostend – Operation Z-O. Under the cover of clouds and smoke, over 70 ships and an assault force of 1,800 Royal Marines embarked on a daring mission which involved a vicious battle of incredible intensity. However, despite the gallant and courageous efforts of the attackers, 11 of whom were later awarded the Victoria Cross, the raid was only partly successful. Discover the successes and failures of this dramatic raid in this in-depth account, complete with specially commissioned battlescene artwork. The author reveals how despite failure, the raid demonstrated to Germany that Britain was still capable of offensive action, even as its armies were being forced back.
Häftad, Engelska, 2020
128 kr
Skickas inom 5-8 vardagar
Häftad, Engelska, 2021
128 kr
Skickas inom 5-8 vardagar
Häftad, Engelska, 2023
228 kr
Skickas inom 5-8 vardagar
Häftad, Engelska, 2023
255 kr
Skickas inom 5-8 vardagar