These items are basically portable darkrooms. They are often used by professional photographers and movie makers when they need to unload or load film in dark conditions. Changing tents and bags enable them to do this in any location. A tent will assemble in just a few seconds and it is designed to keep the interior of it cool. It is light proof and it has openings for your arms to fit into so you can work inside of the small tent in the dark. They have domed ceilings to prevent the fabric from touching the film and to keep it dust free. Most tents have small aluminum poles and are easy to pack away and carry as they only weigh a few pounds. Film changing tents and bags come in various sizes, materials and shapes. A small tent costs about $200 and bags range from about $20 to $80.