Newer methods of card marking make use of what is now called as shade technology. An example would be luminous marked cards. These are cards that make use of luminosity of the cards when a device such as a special pair of sunglasses or contact lens is used on them. Without the device, the cards may look like ordinary cards to onlookers. But with the sunglasses on, the cards can be seen differently along with the marks made on them.
There are also cards that are marked by the way that a deck of cards are designed. Some special cards may contain visible but tiny marks that can only be read by trained magicians who can read the tiny marks that double as codes. Sometimes marked card readers use eyeglasses in order to better read the tiny but unnoticeable to the untrained eye type of marks on the cards. These types of cards are usually designed so that the marked cards can be read from even a distance while another person may be holding them.
Marked cards outside the magic arena are used by some as a means to cheat at casinos or when gambling. In order to prevent this from happening, there are also other ways in which people can detect whether marked cards are being used. One of the most common ways of detecting them is by riffling or shuffling them. This method is commonly called as a gambler's riffle test.
It is simply done by riffling the cards carefully. If a deck of cards is marked, the marks will usually be noticed as if dancing from the back of the cards just like a cartoon drawn on each card back. This can be effective in detecting marked cards with physical marks such as tiny holes or depressions on them.