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4KのクリップをUHDのタイムラインに置くと、わずかに、静かに、スケールまたはクロップされます。ファイルのバッジに書かれた名前はどちらなのかを教えてくれません——実際のピクセル寸法だけが教えてくれます。",{"type":24,"tag":43,"props":1583,"children":1585},{"id":1584},"_1080p2160p4k命名の反転",[1586],{"type":29,"value":1587},"1080p・2160p・4K——命名の反転",{"type":24,"tag":25,"props":1589,"children":1590},{},[1591,1593,1598,1600,1605],{"type":29,"value":1592},"古い規格は",{"type":24,"tag":32,"props":1594,"children":1595},{},[1596],{"type":29,"value":1597},"高さ",{"type":29,"value":1599},"で名付けられていることに注意してください——480、720、1080。一方、4Kと8Kはおおよその",{"type":24,"tag":32,"props":1601,"children":1602},{},[1603],{"type":29,"value":1604},"幅",{"type":29,"value":1606},"で名付けられています。つまり1080pと2Kはほぼ同じもので、「2160p」と「4K」は完全に同じものです。この反転がはしごの途中で起きるため、はしごは実際より大きなジャンプに聞こえます。1080→4Kは「ほぼ4倍」に読めますが、高さで言えば1080→2160に過ぎません。",{"type":24,"tag":25,"props":1608,"children":1609},{},[1610,1612,1616,1618,1623,1625,1630,1631,1636],{"type":29,"value":1611},"文字にも意味があります。1080pの",{"type":24,"tag":32,"props":1613,"children":1614},{},[1615],{"type":29,"value":25},{"type":29,"value":1617},"は",{"type":24,"tag":1207,"props":1619,"children":1620},{},[1621],{"type":29,"value":1622},"プログレッシブ",{"type":29,"value":1624},"——すべてのフレームが完全な一枚絵で、上から下へ描画されます。1080iの",{"type":24,"tag":32,"props":1626,"children":1627},{},[1628],{"type":29,"value":1629},"i",{"type":29,"value":1617},{"type":24,"tag":1207,"props":1632,"children":1633},{},[1634],{"type":29,"value":1635},"インターレース",{"type":29,"value":1637},"——各「フレーム」が交互の走査線による二枚の半端な絵で構成される、アナログ放送から受け継いだ帯域節約の技です。二つの信号がどちらも「1080」を名乗りながら、片方がプログレッシブで片方がインターレースなら、動きの見え方は目に見えて違います。現代のカメラとインターネット全体はプログレッシブで、インターレースは主に放送チェーンとレガシーアーカイブに生き残っています。",{"type":24,"tag":43,"props":1639,"children":1641},{"id":1640},"画素数が多い-シャープな映像",[1642],{"type":29,"value":1643},"画素数が多い ≠ シャープな映像",{"type":24,"tag":25,"props":1645,"children":1646},{},[1647,1649,1653],{"type":29,"value":1648},"最も重要な誤読がこれです。解像度はディテールの",{"type":24,"tag":1207,"props":1650,"children":1651},{},[1652],{"type":29,"value":1263},{"type":29,"value":1654},"を決めるだけで、そこにどれだけ近づけるかは他のすべてが決めます。",{"type":24,"tag":25,"props":1656,"children":1657},{},[1658,1663,1665,1670],{"type":24,"tag":32,"props":1659,"children":1660},{},[1661],{"type":29,"value":1662},"ピクセルには餌が必要です。",{"type":29,"value":1664}," すべてのフレームはビットレート予算を持つエンコーダーを通過します。予算を上げずに画素数を4倍にすれば、エンコーダーはピクセルあたりに使えるビットを減らします——ディテールは軟調になり、動きは滲み、追加の解像度が防ぐはずだったまさにそのアーティファクトが現れます。強く圧縮された「4K」配信が、良くエンコードされた1080pのBlu-rayより悪く見えるのはこのためです。ディスクの潤沢なビットレートは2メガピクセルを適切に満たし、配信は8メガピクセルを飢えさせているのです。このトレードオフは",{"type":24,"tag":191,"props":1666,"children":1667},{"href":1245},[1668],{"type":29,"value":1669},"ビットレートの記事",{"type":29,"value":1671},"で詳しく扱っています。",{"type":24,"tag":25,"props":1673,"children":1674},{},[1675,1680],{"type":24,"tag":32,"props":1676,"children":1677},{},[1678],{"type":29,"value":1679},"ピクセルはそもそも存在しなければなりません。",{"type":29,"value":1681}," 甘いレンズ、ノイズの多いセンサー、外れたフォーカス、モーションブラーは、上限の下にさらに低い天井を作ります——軟調な画の4K収録は、軟調な画の大きなファイルです。4Kで記録しても、光学系が届けなかったディテールは追加されません。",{"type":24,"tag":25,"props":1683,"children":1684},{},[1685,1690],{"type":24,"tag":32,"props":1686,"children":1687},{},[1688],{"type":29,"value":1689},"シャープネスは知覚です。",{"type":29,"value":1691}," 「シャープ」と感じられるものの正体は、主にエッジのコントラストと微細なテクスチャの再現であって、生の画素数ではありません。パリッとした、良くグレーディングされた1080pが、フラットでノイジーな4Kよりシャープに見えることは日常的にあります。",{"type":24,"tag":25,"props":1693,"children":1694},{},[1695,1697,1702],{"type":29,"value":1696},"解像度はファイルがどれだけのディテールを",{"type":24,"tag":1207,"props":1698,"children":1699},{},[1700],{"type":29,"value":1701},"保持できるか",{"type":29,"value":1703},"を教えてくれます。実際に保持しているかどうかは、上流のすべてが決めます。",{"type":24,"tag":43,"props":1705,"children":1707},{"id":1706},"そもそも見えるのか視聴距離",[1708],{"type":29,"value":1709},"そもそも見えるのか？——視聴距離",{"type":24,"tag":25,"props":1711,"children":1712},{},[1713],{"type":29,"value":1714},"目の分解能は有限で、ピクセルは目が分解できる視角に達して初めて意味を持ちます。変数は画面サイズと距離です。",{"type":24,"tag":25,"props":1716,"children":1717},{},[1718,1720,1725],{"type":29,"value":1719},"55インチのテレビを典型的なソファ距離2.5〜3メートルで見るとき、1080pと4Kの区別は本当に困難です——追加のピクセルは目が分離できる大きさを下回っています。同じパネルを1.5メートルに近づけるか、腕の長さの27インチモニターに切り替えるか、スマホを顔から30cmで持てば、差ははっきり見えます。これが「Retina」ディスプレイの論理のすべてです。ピクセル密度は、",{"type":24,"tag":1207,"props":1721,"children":1722},{},[1723],{"type":29,"value":1724},"その画面を実際に使う距離で",{"type":29,"value":1726},"目に勝ちさえすればよいのです。",{"type":24,"tag":25,"props":1728,"children":1729},{},[1730],{"type":29,"value":1731},"実務的に言えば：4K納品が報われるのは、画面が視野の大きな部分を占めるとき——モニター、近くで見る大型テレビ、映画館、VR。部屋の向こうのテレビやWebページに埋め込まれた動画では、良くエンコードされた1080pと視覚的に区別できないことがよくあります。",{"type":24,"tag":43,"props":1733,"children":1735},{"id":1734},"それでも4kで撮る理由オーバーサンプリングと余白",[1736],{"type":29,"value":1737},"それでも4Kで撮る理由——オーバーサンプリングと余白",{"type":24,"tag":25,"props":1739,"children":1740},{},[1741,1743,1748],{"type":29,"value":1742},"1080p納品で十分なことが多いなら、なぜほぼ全員が4Kで撮るのでしょうか。収録解像度と納品解像度は別の目的に仕えるからです。収録時の追加ピクセルは",{"type":24,"tag":1207,"props":1744,"children":1745},{},[1746],{"type":29,"value":1747},"ワークフローの余白",{"type":29,"value":1749},"です。",{"type":24,"tag":330,"props":1751,"children":1752},{},[1753,1763,1773,1797],{"type":24,"tag":334,"props":1754,"children":1755},{},[1756,1761],{"type":24,"tag":32,"props":1757,"children":1758},{},[1759],{"type":29,"value":1760},"リフレーミング。",{"type":29,"value":1762}," 1080pタイムライン上の4K素材は、画質劣化ゼロで最大2倍までパンチインできます——構図の取り直し、疑似的な2カメ目、フレーム端の邪魔者の排除。",{"type":24,"tag":334,"props":1764,"children":1765},{},[1766,1771],{"type":24,"tag":32,"props":1767,"children":1768},{},[1769],{"type":29,"value":1770},"スタビライズ。",{"type":29,"value":1772}," ソフトウェア手ぶれ補正はクロップとシフトで動きます。余剰解像度こそが補正の切りしろです。ネイティブ1080pの補正は目に見えるシャープネスを代償にしますが、1080p納品のための4K補正はタダです。",{"type":24,"tag":334,"props":1774,"children":1775},{},[1776,1781,1783,1788,1790,1795],{"type":24,"tag":32,"props":1777,"children":1778},{},[1779],{"type":29,"value":1780},"オーバーサンプリング。",{"type":29,"value":1782}," 4Kを1080pにダウンスケールした映像は、ネイティブ1080p収録より",{"type":24,"tag":1207,"props":1784,"children":1785},{},[1786],{"type":29,"value":1787},"良く",{"type":29,"value":1789},"見えます。ノイズは平均化され、エッジはクリーンに描画され、4:2:0で収録した4Kのクロマディテールは1080pでほぼ4:4:4相当になります——",{"type":24,"tag":191,"props":1791,"children":1792},{"href":1253},[1793],{"type":29,"value":1794},"クロマサブサンプリング",{"type":29,"value":1796},"された素材にとって実質的なアップグレードです。",{"type":24,"tag":334,"props":1798,"children":1799},{},[1800,1805],{"type":24,"tag":32,"props":1801,"children":1802},{},[1803],{"type":29,"value":1804},"将来への備え。",{"type":29,"value":1806}," アーカイブマスターは納品フォーマットより長生きします。今日4Kで撮った素材は今後何年も綺麗に再納品できます。10年前の1080pマスターは、いまやリマスターの制約要因です。",{"type":24,"tag":25,"props":1808,"children":1809},{},[1810,1812,1817,1819,1824],{"type":29,"value":1811},"逆方向——",{"type":24,"tag":32,"props":1813,"children":1814},{},[1815],{"type":29,"value":1816},"アップスケーリング",{"type":29,"value":1818},"——は、収録されなかったものを取り戻せません。古典的な補間はディテールの増えない滑らかな拡大画像を作るだけで、MLアップスケーラーは本物のディテールを復元するのではなく、もっともらしいディテールを",{"type":24,"tag":1207,"props":1820,"children":1821},{},[1822],{"type":29,"value":1823},"発明",{"type":29,"value":1825},"します。納品の仕上げには十分なことも多いですが、アーカイブにおいては正直でいる価値があります。世の中の「4K」ファイルのかなりの数はアップスケールされた1080pマスターで、メタデータはそれを白状してくれません。",{"type":24,"tag":43,"props":1827,"children":1829},{"id":1828},"ピクセルのコスト",[1830],{"type":29,"value":1828},{"type":24,"tag":25,"props":1832,"children":1833},{},[1834],{"type":29,"value":1835},"「4倍」はすべての請求書に現れます。",{"type":24,"tag":330,"props":1837,"children":1838},{},[1839,1857,1867],{"type":24,"tag":334,"props":1840,"children":1841},{},[1842,1847,1849,1855],{"type":24,"tag":32,"props":1843,"children":1844},{},[1845],{"type":29,"value":1846},"ビットレートとストレージ。",{"type":29,"value":1848}," 画素数4倍がちょうど4倍のビットレートを要求するわけではありません——エンコーダーは細部の冗長性を利用するので、典型的には2〜3倍です——が、同等画質の4Kファイルは1080pの数倍のサイズになります。これこそがH.265とAV1の普及を後押しした圧力で、",{"type":24,"tag":191,"props":1850,"children":1852},{"href":1851},"/ja/articles/video-codec-comparison",[1853],{"type":29,"value":1854},"コーデックの記事",{"type":29,"value":1856},"で扱ったとおりです。H.264での4K納品はつらく、HEVCなら日常です。",{"type":24,"tag":334,"props":1858,"children":1859},{},[1860,1865],{"type":24,"tag":32,"props":1861,"children":1862},{},[1863],{"type":29,"value":1864},"処理。",{"type":29,"value":1866}," エンコード、デコード、デベイヤー、グレーディング、レンダリング、すべてが4倍のピクセルを相手にします。4Kをスムーズに編集するためにプロキシワークフローが存在し、8Kの編集ではそれが必須になります。",{"type":24,"tag":334,"props":1868,"children":1869},{},[1870,1875,1877,1883],{"type":24,"tag":32,"props":1871,"children":1872},{},[1873],{"type":29,"value":1874},"モードのトレードオフ。",{"type":29,"value":1876}," カメラのセンサーには読み出し速度の上限があるため、解像度は",{"type":24,"tag":191,"props":1878,"children":1880},{"href":1879},"/ja/articles/frame-rate-basics",[1881],{"type":29,"value":1882},"フレームレート",{"type":29,"value":1884},"とトレードされます——4K 60fpsで撮れる同じカメラが、1080pなら240fpsで撮れたりします。収録モードを選ぶことは、そのショットに必要なディテールの種類（空間か時間か）を選ぶことです。",{"type":24,"tag":25,"props":1886,"children":1887},{},[1888,1890,1895,1897,1902],{"type":29,"value":1889},"8Kについては冷静な注記を。",{"type":24,"tag":1207,"props":1891,"children":1892},{},[1893],{"type":29,"value":1894},"納品",{"type":29,"value":1896},"フォーマットとしてはほぼすべての視聴環境で人間の視力を超えてしまいますが、",{"type":24,"tag":1207,"props":1898,"children":1899},{},[1900],{"type":29,"value":1901},"収録",{"type":29,"value":1903},"フォーマットとしてはオーバーサンプリングとリフレーミングの余白をもう一段先に進めたものです——そして実際、主にそう使われています。",{"type":24,"tag":43,"props":1905,"children":1907},{"id":1906},"メタデータの中の解像度符号化寸法と表示寸法",[1908],{"type":29,"value":1909},"メタデータの中の解像度——符号化寸法と表示寸法",{"type":24,"tag":25,"props":1911,"children":1912},{},[1913],{"type":29,"value":1914},"動画ファイルの他のすべてと同じく、解像度もメタデータに宣言されます——そして中には思った以上に多くの「寸法」があります。",{"type":24,"tag":66,"props":1916,"children":1918},{"code":1917},"Stream #0:0: Video: h264\n  Width: 1920, Height: 1080\n  Coded width: 1920, Coded height: 1088\n  Sample Aspect Ratio: 1:1\n  Display Aspect Ratio: 16:9\n",[1919],{"type":24,"tag":71,"props":1920,"children":1921},{"__ignoreMap":7},[1922],{"type":29,"value":1917},{"type":24,"tag":25,"props":1924,"children":1925},{},[1926,1931],{"type":24,"tag":32,"props":1927,"children":1928},{},[1929],{"type":29,"value":1930},"Coded（符号化）寸法",{"type":29,"value":1932},"は、コーデックが実際に処理するサイズです。H.264は16×16のマクロブロック単位で動作し、1080は16で割り切れないため、エンコーダーは1088にパディングし、クロップフラグがプレーヤーに「1080行だけ表示せよ」と伝えます。無害です——ツールが間違ったフィールドを読んで1088と報告したり、最悪の場合パディングまで表示したりするまでは。",{"type":24,"tag":25,"props":1934,"children":1935},{},[1936,1941],{"type":24,"tag":32,"props":1937,"children":1938},{},[1939],{"type":29,"value":1940},"サンプルアスペクト比（SAR）",{"type":29,"value":1942},"は、先ほどの非正方形ピクセルの話です。720×480で格納されたSDファイルはSAR 10:11で4:3として表示されます。格納寸法だけを読むと、ライブラリ内のすべてのSD素材について、形と実効解像度の両方を見誤ります。アナモルフィック収録は同じことをより高い解像度で行います。",{"type":24,"tag":25,"props":1944,"children":1945},{},[1946],{"type":29,"value":1947},"つまり「このファイルの解像度は？」には本当に複数の答え——格納、符号化、表示——があり、それらを混同するツールが古典的な謎を生みます。1088行のファイル、潰れて見えるDVクリップ、プレビューで横に伸びるアナモルフィックマスター。",{"type":24,"tag":43,"props":1949,"children":1951},{"id":1950},"ライブラリの解像度タグが重要な理由",[1952],{"type":29,"value":1950},{"type":24,"tag":25,"props":1954,"children":1955},{},[1956],{"type":29,"value":1957},"現場のライブラリが単一解像度であることはまずありません。UHDやDCI 4Kのカメラマスター、1080pのプロキシ、非正方形ピクセルのレガシーSD素材、モニター解像度そのままのスクリーン録画、縦型1080×1920のスマホクリップ——すべてが混在し、すべてが「動画」というラベルを付けています。",{"type":24,"tag":25,"props":1959,"children":1960},{},[1961],{"type":29,"value":1962},"VideoTaggerはライブラリをインデックスする際、すべてのクリップの実際のピクセル寸法を——コーデック・ビットレート・フレームレートとともに——検索可能にします。これにより次のことが可能になります。",{"type":24,"tag":330,"props":1964,"children":1965},{},[1966,1971,1976,1981],{"type":24,"tag":334,"props":1967,"children":1968},{},[1969],{"type":29,"value":1970},"4Kカメラマスターと1080pのプロキシ・納品物を、ファイルを開かずに一目で分離",{"type":24,"tag":334,"props":1972,"children":1973},{},[1974],{"type":29,"value":1975},"UHD（3840×2160）素材に紛れたDCI 4K（4096×2160）クリップを、同一タイムラインで混ざる前に発見",{"type":24,"tag":334,"props":1977,"children":1978},{},[1979],{"type":29,"value":1980},"表示上の形が格納寸法と一致しないレガシーSD・アナモルフィック素材を洗い出し",{"type":24,"tag":334,"props":1982,"children":1983},{},[1984],{"type":29,"value":1985},"解像度とビットレートを組み合わせて実際の品質を判断——ビット不足で飢えている不審に小さな「4K」ファイルや、安価な複製で足りるストレージ食いのマスターをフラグ付け",{"type":24,"tag":25,"props":1987,"children":1988},{},[1989,1991,1996],{"type":29,"value":1990},"解像度は、誰もが動画ファイルから最初に読み取る数字です。それが",{"type":24,"tag":1207,"props":1992,"children":1993},{},[1994],{"type":29,"value":1995},"正しい",{"type":29,"value":1997},"数字であること——実際の寸法が、正しく解釈されていること——が、ライブラリの他のすべてが乗る土台になります。",{"type":24,"tag":43,"props":1999,"children":2000},{"id":619},[2001],{"type":29,"value":619},{"type":24,"tag":330,"props":2003,"children":2004},{},[2005,2024,2063,2073,2085,2097],{"type":24,"tag":334,"props":2006,"children":2007},{},[2008,2010,2015,2017,2022],{"type":29,"value":2009},"解像度は",{"type":24,"tag":32,"props":2011,"children":2012},{},[2013],{"type":29,"value":2014},"ピクセルグリッド",{"type":29,"value":2016},"——幅×高さ。ファイルが保持",{"type":24,"tag":1207,"props":2018,"children":2019},{},[2020],{"type":29,"value":2021},"できる",{"type":29,"value":2023},"ディテールの上限であり、実際に保持するかはビットレート・光学系・処理が決める",{"type":24,"tag":334,"props":2025,"children":2026},{},[2027,2029,2034,2036,2041,2043,2047,2049,2054,2056,2061],{"type":29,"value":2028},"規格の階段：SD（720×480/576）、720p、",{"type":24,"tag":32,"props":2030,"children":2031},{},[2032],{"type":29,"value":2033},"1080p",{"type":29,"value":2035},"（2.1 MP）、",{"type":24,"tag":32,"props":2037,"children":2038},{},[2039],{"type":29,"value":2040},"UHD 4K",{"type":29,"value":2042},"（3840×2160、8.3 MP）、",{"type":24,"tag":32,"props":2044,"children":2045},{},[2046],{"type":29,"value":1476},{"type":29,"value":2048},"（4096×2160）、",{"type":24,"tag":32,"props":2050,"children":2051},{},[2052],{"type":29,"value":2053},"8K",{"type":29,"value":2055},"（33.2 MP）——大きな段差は",{"type":24,"tag":32,"props":2057,"children":2058},{},[2059],{"type":29,"value":2060},"画素数4倍",{"type":29,"value":2062},"で、その4倍はビットレート・ストレージ・処理コストに付いて回る",{"type":24,"tag":334,"props":2064,"children":2065},{},[2066,2071],{"type":24,"tag":32,"props":2067,"children":2068},{},[2069],{"type":29,"value":2070},"「4K」は二つの規格",{"type":29,"value":2072},"：DCI 4096×2160（シネマ）とUHD 3840×2160（コンシューマー全般）——タイムラインで混ぜると静かにスケールまたはクロップされる",{"type":24,"tag":334,"props":2074,"children":2075},{},[2076,2078,2083],{"type":29,"value":2077},"画素数が多い≠シャープ：",{"type":24,"tag":32,"props":2079,"children":2080},{},[2081],{"type":29,"value":2082},"飢えた4K配信は良くエンコードされた1080pディスクに負けうる",{"type":29,"value":2084},"し、ソファ距離ではそもそも差が見えないことも多い",{"type":24,"tag":334,"props":2086,"children":2087},{},[2088,2090,2095],{"type":29,"value":2089},"納品解像度より上で撮ることは本物の余白を買う——",{"type":24,"tag":32,"props":2091,"children":2092},{},[2093],{"type":29,"value":2094},"リフレーミング、スタビライズ、オーバーサンプリング",{"type":29,"value":2096},"（4K→1080pはほぼ4:4:4クロマ相当）、将来も使えるマスター。アップスケーリングはその逆を偽装することしかできない",{"type":24,"tag":334,"props":2098,"children":2099},{},[2100,2102,2107],{"type":29,"value":2101},"ファイルには",{"type":24,"tag":32,"props":2103,"children":2104},{},[2105],{"type":29,"value":2106},"格納・符号化・表示",{"type":29,"value":2108},"の寸法がある（1088行のパディング、SDの非正方形ピクセル）——間違った寸法を読むことが、解像度の謎の出どころ",{"title":7,"searchDepth":655,"depth":655,"links":2110},[2111,2112,2113,2114,2115,2116,2117,2118,2119,2120,2121],{"id":1216,"depth":655,"text":1216},{"id":1273,"depth":655,"text":1273},{"id":1549,"depth":655,"text":1552},{"id":1584,"depth":655,"text":1587},{"id":1640,"depth":655,"text":1643},{"id":1706,"depth":655,"text":1709},{"id":1734,"depth":655,"text":1737},{"id":1828,"depth":655,"text":1828},{"id":1906,"depth":655,"text":1909},{"id":1950,"depth":655,"text":1950},{"id":619,"depth":655,"text":619},"content:articles:ja:video-resolution-explained.md","articles/ja/video-resolution-explained.md","articles/ja/video-resolution-explained",{"_path":2126,"_dir":5,"_draft":6,"_partial":6,"_locale":7,"title":2127,"description":2128,"slug":2129,"date":2130,"image":2131,"category":1189,"tags":2132,"body":2136,"_type":669,"_id":3111,"_source":671,"_file":3112,"_stem":3113,"_extension":674},"/articles/ja/hdr-explained","HDR入門 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Visionをデコードできないディスプレイでも有効なHDR10の絵が得られます。動的メタデータにより、性能の控えめなディスプレイでも、作品中で最も明るい一瞬に縛られることなく、各シーンを独自の条件でトーンマッピングできます。",{"type":24,"tag":25,"props":2523,"children":2524},{},[2525,2530],{"type":24,"tag":32,"props":2526,"children":2527},{},[2528],{"type":29,"value":2529},"HDR10+",{"type":29,"value":2531},"は、Samsung主導のDolby Visionへのロイヤリティフリーな回答です。HDR10のベースライン——10bit、PQ、Rec.2020——に動的なシーン単位メタデータを追加し、ライセンス費用は不要ですが、Dolby Visionが12bitまで対応するのに対しHDR10+は10bitまでです。",{"type":24,"tag":25,"props":2533,"children":2534},{},[2535,2537,2542],{"type":29,"value":2536},"実務的な要点：",{"type":24,"tag":32,"props":2538,"children":2539},{},[2540],{"type":29,"value":2541},"HDR10＝静的・一律、Dolby VisionとHDR10+＝動的・シーンごとに適応。",{"type":29,"value":2543}," 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