AmericanfilmcriticElvisMitchell’skaleidoscopicdocumentarycreatesadefinitivenarrativeoftheBlackrevolutionin1970scinema,fromgenrefilmstosocialrealism—aworkofpainstakingscholarshipthat’salsothoroughlyentertaining,anessentialarchivaldocumentandtestamenttoaperiodofAmericanfilmhistoryunlikelytoberepeatedaaa