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Fotothek df tg Optik Instrument Dioptrik Linse Fokus Licht. Scan Deutsche Fotothek dftg color MIKCenter Berlin GmbH Tabula Lib Wien Frankfurt Main Sammellinsen Bndel parallel verlaufender einfallender Lichtstrahlen werden im Brennpunkt gesammelt Papier Kupferstich cm Optik Instrument Dioptrik Linse Fokus Licht ppnX Druck