Here is a photo of a camera system that had been used extensively in the making and testing of various marked cards. Although this system was only used in "laboratory conditions" similar camera systems have been used quite frequently in actual game settings. Although this system is basically an electronic version of a luminous system, such as the luminous contact lenses, it doesn't actually use quite the same technology. In other words, the inks for a camera system are different than those used for luminous systems. The reason is because cameras are able to pick up wavelengths of light that are completely invisible to human eyes, with or without filters.
When these camera systems are used in actual play, there is always a team involved; at least two people, one posing as a player and the other monitoring the game in a separate room. But basically, the camera is strategically-placed in such way that will offer a good view of the entire card table (sometimes several cameras are used). The video signal from the camera is fed into a control room, where one member of the team is able to play back the initial distribution of the cards, in privacy. Once this team member knows what cards all the players are holding in their hands, this team member (not the player) makes playing decisions. All that remains to be done is to send a set of simple signals (for example: check, bet, raise, fold) to the player. This can be accomplished with the use of an RF communication unit or by any other means, including the involvement of another person that is apparently not even involved in the game (posing as a waitress, or anything along those lines).
First camera systems were reportedly sold for a hefty sum of $20,000. This price tag dates back to the 1980's when technology was not as readily available as it is today. Due to the availability of technology these systems came down in price, quite significantly and nowadays one can buy a basic functional camera system for a fraction of what it used to cost.
The ink is a different story, however, and at the time of this writing a good ink will still have a high price tag. Cheaper inks will do the job but they will not produce very dark marks and they can also be seen through a variety of luminous filters. Also, cheaper inks may be detectable without any glasses, contacts or cameras if the work on the cards is too strong in the effort to make the marks read darker on camera. Some cheaper inks will also produce an alcohol burn on the finish of some playing cards. This can usually be covered up, but all these details are reasons why a good ink will still be on the expensive side - although some may consider it a bargain.
A video demo of an early camera system can be viewed on our Video-Juice Camera System video demo page.