閱讀光學(xué)文獻(xiàn)時(shí)對(duì)其中的“enlarging on paper with hard gradation”無法理解，求大神指教，謝謝！ ;@hP*7Lm  
“When black-and-white photography was still dominant, one could compensate the low contrast reproduction of these lenses by enlarging on paper with hard gradation.”