Several years ago I had an approximately DIN A5 large gray card made of cardboard, it had a gray tone, which was standardized for the exposure. Now I wanted to use here with the 3 plastic cards to replace this set. But accurate measurements are not possible with these cards. Depending on what angle you align these cards to the camera or light, the value for white balance or exposure is another. So exactly I can not keep perpendicular to the lens, as that read at the camera white balance or exposure are reliably my hand and thus the cards. So the post-processing and fine tuning of white balance and exposure in Photoshop will not be spared. It is totally unnecessary, perhaps to achieve a 50% better white balance or a 50% better exposure with these cards. Because almost exact values can be achieved with automatic settings today with any camera. Since the cards would therefore have been 100% bring so one will be spared the post. - The black card is also used to calculate an accurate black level in the later post useless, since this card is displayed (depending on the light) in black or any shade of gray on the test photo.
