18% Photo Gray Cards are for use in forensic photography. These cards are useful in determining exposure, lighting ratio, and color balance in photographs and film. Place an 18% Photo Gray Card in a camera shot as a frame of color reference, then use its neutral gray color as a standard for in-camera white balancing or post-process white balancing. When you use 18% Photo Gray Cards at the start of every shooting location and light source, it provides the simplest way to ensure all your pictures are perfectly colored and evenly balanced with each other. No camera bag is complete without a set of 18% Photo Gray Cards. Each set will come with a complete set of instructions on how to use the 18% Photo Gray Cards and are protected in a clear zip poly bag.