PRODUCT INFOMATION:

• 18% grey is used in the digital grey card as a base color.
• Both grey and white surfaces of the grey card have their own function.
• Whatever you used in film or digital photography, an 18% grey card white balance can control expose value and balance the color so that it helps to revert the color truly and perfectly by measuring the exposure value, white/grey balance value and color temperature.
• A grey card had been invented based on the optical principle and the characteristic of photosensitive film.
• The camera exposure value is in direct ratio with the logarithm of characteristic curve. Characteristic curve shows two important features of photosensitive material (they are: contrast factor and exposure latitude), and it is in coordinate with the sense of human sight in reflection to the colors in ray.
• When color changes as geometric progression, its density will change as arithmetic progression. If we try to get a series of density values like 1:2:3:4:5……, the exposure value will be increased like 1:2:4:8:16…., always in multiple.
• If we set the reflection ratio to 100% (as maximum) and decrease progressively as common ratio of 2, we'll get the density value of full-level diaphragm: 100, 50, 25, 12.5, 6.25, 3.125…… if the reflection ratio decrease progressively as square root of 2, we'll get the density value of half-level diaphragm: 100, 70.71, 50.35, 36.25, 17.68, 12.5, 8.84, 6.25, 4.42, 3.125…… Actually those values are just different grey values in different grades.
• We take it that the standard exposure value is 17.68, then those values beside it will be its exposure latitude.
• Look at those density values above, from number 100 to 3.125, the ratio is 32:1.
• The exposure latitude in this ratio is exactly included in the photosensitive range among in color negative, black/white negative, color reversal film and CCD.
• We'll see that 17.68 is just right in the middle of those series of numbers.
• Thus, it will be excellent and precise to take 17.68 (approximation of 18%) as a base value, which controls the exposure value, photographic density and color balance.
• In manufacturing of photosensitive products, 18% grey had become a standard in theory because of its special characteristic.
• 18% grey as a foundation used in the photographic sensitivity of the film, the exposure value of exposure photometer, CCD and CMOS sensors.

Specification:

• Gray side: Reflectance 17.8%;
• Density 0.74
• White side: Reflectance 92.0%;
• Density 0.036
• Max.
• Deviation of reflectance: 2%
• Max.
• Error in exposure measurements: 1/8 of F-stop
• Card sizes: 4""x6""and 6""x8""
• Core material: high density paper based composite
• Gray side material: special paper with spectrally flat 18% coating
• White side material: special paper with spectrally flat 18% coating

Contains:

• 4 "" x6"" Grey/White Card x1
• 6 "" x8"" Grey/White Card x1
• English User Manual (A CD Card) x1
•  Original Manufactory Package
• Size: 215*65*5mm