There are certain times when people absolutely can not take pictures of other people without their consent. The most common instance would be when the pictures are going to be used for any commercial purpose. A commercial purpose could be any activity in which the photograph (or film/video) is being used by someone to make money. Examples are the filming of sporting events, concerts, location shoots at the local mall by a television crew, or any other activity in which someone is pointing a camera at people randomly. This is why you often see signs in public places that have warnings like the following: 'by entering this area, you agree to be photographed or filmed.' Without your 'agreement', your image can't be used by the photographer.

Another related situation in which someone might be photographed would be where there are in a private place, for example in your back-yard with the photo being taken over a fence. This commonly happens with celebrities who are being photographed from helicopters, trees, or boats. As with the commercial use example above, this also is not legal, but the subject of the photo might be able to sue for 'invasion of privacy' for such an intrusion.

To give consent to be photographed, a very basic paper form is normally carried by professional photographers that gives consent for the photo or video to be used however the producer sees fit. If the subject (such as your son) is a minor, then only the minor's legal guardian, can give permission for them to be photographed.

With all of that said, there could situations in which consent is somehow implied, which means you may give consent by entering into a relationship with the photographer. If your son were in some kind of school activity or other paid activity (like a camp of some kind), the business might have implied consent to photograph the participants for their records, promotional activities or even security purposes. These 'uses' of the photographs aren't usually considered commercial and may be considered necessary for the operation of the business.

In most cases, it is best to ask, 'why am I (or is my child) being photographed?' and go from there. If the answer is that someone is taking pictures to use to make money, then they probably need to have consent. If the use is for some other purpose, then they may not need it.