The grey card is a help in situations when you need a reference value to get the right reproduction. Since you are not able to take the subject which you want to photograph to the lab you just reverse the process. Take the card to the location and compare your pictures later-on in the lab with the original card. details: - Format DIN A 4 (210 x 296 mm) - strength: 2 mm - material: polystyrol white - light-fastness: 7-8 blue scale - color: neutral grey DN=0,75 log D = 17,68 % reflexion - washable
