When producers shoot a scene at a place open to the public people in the background might be captured on camera. It is often not practicable to get every member of the crowd to sign a release. Consequently, producers may post a sign at the entrances to the event alerting participants that they may be captured on screen and stating that by entering the venue they are consenting to be recorded. Alternatively, a release might be presented to persons when they purchase a ticket to an event and printed on the ticket as well.
Persons do not have an absolute legal right to prevent publication of any photo taken of them without their permission. If every person had such a right, no photo could be published of a street scene or a parade. Liability usually exists only if publication of a photo would be offensive to people of ordinary sensibilities, or is defamatory or invades their right of privacy. See, for example, Gill v. Hearst Publishing, 40 Cal. 2d 224 (1953). However, the use of a person's image or likeness without their permission to sell a product would likely infringe their right of publicity and give rise to liability.
If you are using a posted crowd release, it is good practice to take a photo of all the entrances with the sign clearly posted in public view. The notice should be large enough that those passing by will clearly see it.
CROWD RELEASE (sample)
(Post outside of entry doors or on perimeter of filming area)
By entering and by your presence here, you consent to be photographed, filmed and/or otherwise recorded. Your entry constitutes your consent to such photography, filming and/or recording and to any use, in any and all media throughout the universe in perpetuity, of your appearance, voice and name for any purpose whatsoever in connection with the production presently entitled: ________________________.
You understand that all photography, filming and/or recording will be done in reliance on this consent given by you by entering this area.
If you do not agree to the foregoing, please do not enter this area.