The QPcard 101 Calibration Card is a small, lightweight and inexpensive way to calibrate your contrast. A pad of 3 QPcards comes in a protective resealable foil bag that fits easily into a camera case or pocket. There is a millimeter reference scale on the card.
The cards have adhesive on the back so that they can be attached to virtually any surface
The gray surface is completely neutral and reflects 18% light, with a white and black patch that can be used for contrast adjustment as well as a dimensional reference
A guaranteed neutral gray surface in the image simplifies color balancing
Even with correctly set and calibrated computers, software and monitors, you must balance a digital image against the monitor
It is complicated to carry around a larger gray card and position it at a suitable place in the subject. In addition, a traditional gray card becomes dirty and faded from the light, so that after a while it is no longer neutral gray