The majority of breeds that are considered "'very light shedders" are usually the breeds that need to be clipped, stripped and/or scissored. Because their hair falls out at a much slower rate, if they are not properly groomed they are prone to matting.
Some breeds have a seasonal shedding season in the spring, as their winter coats are lost. But if your dog is an indoor dog it may not be outside enough for its body to register the change of season, so he may shed all year round. Today dogs are bred mostly as companions and some breeds are not meant to live outdoors, so do not start leaving your dog outside all day long in hopes of stopping the shedding. Longhaired dogs may appear to shed more, but it is really just the length of their hair that gives that illusion.