Interesting article discusses how “license plate sprays” and other attempts to conceal license plate photographs are ineffective.

http://articles.moneycentral.msn.com/Insurance/article.aspx?post=1798834

Some “masking” products let us apply a cover or spray to license plates to neutralize the devices.  The spray or cover supposedly reflects the camera’s flash and overexposes the photo, rendering it useless.  However, a new study of some of those products by the Los Angeles Police Department — experts on the “California stop” — shows they don’t work and, in some cases, actually improve the image quality.

“The countermeasures had no effect on plate legibility under dark conditions, with the exception of V-2 (license plate shield), which occasionally caused a slight increase in front-plate legibility in half of the images. … All rear plate images were clearly legible, with no significant difference between the test plate images and the control plate image. A citation could have been issued in all cases,” the study said.

Oh well.  Back to the drawing board . . .