[mendel]

What is purpose of black / white / grey card? When it wil be used and where to buy it (or just ordinary paper card and do it by yourself)????

[Philippe]

黑咭用來遮光,在長時間曝光中途暫時中斷曝光.或遮住光線較強的地方減低反差.
白咭做手動白平衡
灰咭做測光.
買質地好啲,自己做也無不可.

[bikram]

Thanks Philippe. Now I know to use black and white card. However, I still don't know how to use grey card for metering purpose. Can you explain more?

[Philippe]

相機測光是以18%灰為基礎的,其他深淺色會令測光數值有出入.灰咭正好就是18%灰.放在拍攝光源下,覆蓋整個測光範圍,理論上便可以獲得正確的光圈及快門.