This is for one Large plate – 30cm x 30cm (~12 in X 12 in)
Gray Plates for Imaging (Roy Larimer & Neil Cobb)
Background: The 18% gray card was the film standard for use as a neutral background to adjust white balance in imaging. It was a mid-point between black and white where typically 18% of the light reflected back from white is a neutral gray, not blue or red. A 11% Neutral gray background is more appropriate than 18% for digital imaging, although any neutral gray can work (void of color) if imaging with the correct exposure. As long as the exposure is set so the histogram is centered and use that luminance as my baseline for all future calibrations. There are many color checkers and neutral gray cards made of high-quality card stock or plastic.
Gray Plate: These paper and plastic neutral gray cards have a number of quality and longevity issues. Roy Larimer (Visionary Digital) has developed powder-coated aluminum plates that are 11% pantone neutral gray. They have an ultra-smooth texture with no relief, as opposed paper cards, They come in three sizes (See Below, dimensions may vary up to 1-2mm on a side). You can use both sides of the plate, on the smaller plates Roy has put on a pad that can be easily removed with a heat gun. They will last forever if properly cared for, they are UV sensitive and should not be exposed to direct sunlight. They are most easily cleaned with ethanol.