Screen angle indicator: A protractor with many co-centre circles. When placed over a half-tone film or print, indicates by a halo, the screen angle of the half-tone.是什么意思_Screen angle indicator: A protractor with many co-centre circles. When placed over a half-tone film or print, indicates by a halo, the screen angle of the half-tone.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句