Atmospheric frost scenes in the woods were used in Lassie as the seasons change. Fog and frost can be seen in the woods. This is created by pushing smoke or haze into the atmosphere. Foggers and smoke machines are brought on the set. Materials to create powder frost can also be sprayed on surfaces.
In scenes toward the end of the movie, the dog finds himself in an enclosed area with snow. These scenes were relatively easy to make since there are no outdoor scenes requiring extensive snow. Foam was used to create a thin layer of snow on the ground and on surfaces that were above ground level.
The setting of the film is in the '60s so many vintage cars were used. Care must be given to make sure that the time period is authentic. There are several vehicles used in Lassie such as an old train, tractor, trucks and a horse drawn caravan. Mechanical special effects were used to make these machines and forms of transportation move in synchronizatrion in various scenes.
The dogs in Lassie are extremely well trained but not well enough to replace special effects in sequences involving synchronized movement. In several scenes there are a number of dogs that congregate with Lassie. Different photographic effects were used such as multiple exposures to give the illusion of synchronicity. Lassie also occurs in many scenes that must be synchronized photographically.