What is a photoblocker and how does it work? There are two different items that fit the description of the word. First item is what is called a photoblocker license plate cover. The second one is a photoblocker spray. Both are used in the context of a registration plate on a vehicle for a purpose of blocking anybody from taking a picture of it.
The above mentioned plate cover is manufactured from a clear plastic with which you cover your registration number. It is easier to wash your plate after this installation is done, but the main purpose is to avoid photographing of your plate number and not the ease of cleaning it. It works on the similar principle as you trying to take a picture of your image in the mirror while using a flash. When you look at the end result of this attempt you will find out that on the picture there is a big bright spot in the area you focused your camera on. The same happens when you try to take a picture of your license plate with the transparent shield installed over it. The plate cover reflects the flash of the camera. Of course, you can take a picture of any registration plate with the cover installed without the flash option being on, the same as you can take a picture of yourself in the mirror in this way.
Photoblocker spray works exactly on the same principle, except that there is nothing to mount on your plate. You just spray the aerosol solution containing millions of tiny particles that have reflective properties over it. When the flash is triggered, the picture becomes ineligible due to overexposure, the same as with the plate cover.
The advantage of the spray, when compared to the license plate cover, is its price and also the ease of application. I mean anyone can install it within a few minutes without having any experience or special skills. No tools are needed. Another advantage of the spray is that out of one can you can spray up to four plates. The main disadvantage is the fact that eventually the spray wears off. Obviously the time it will stay on and work its magic depends mainly on the weather and climate conditions. Still, no one should expect the spray film to last more than 4 months. A more realistic guess is two months. Hence, if you use the can only for one license plate, it might last you anywhere from eight months to a year (or longer in some rare instances).
Due to its favorable price, ease of application, and legality of use, the photo blocker spray seems to be of a good value. There are several manufacturers of the spray and it has yet to be tested what are the differences between each brand. One manufacturer claims that over 500,000 units were sold worldwide, so if I was to buy a can of this spray, I would look for this particular manufacturer. I am of course aware of the fact that the claim might be just a sale strategy, but it is not up to me to arrive at that conclusion in this article.