Photo lighting filters---or lighting gels---are used to color light coming from either a lamp or flash bulb. One can be used either to balance the temperature of all the lights, or to create a desired lighting effect. For instance, a photographer shooting in a room lit by yellowish tungsten bulbs may wish to use a yellow lighting filter over his white flash so that all sources of light are the same color. Additionally, photographers may use a modeling light with a colored gel pointed to a backdrop to turn a white background into any other color. A photographer may also wish to illuminate his subject with different colors of light for artistic effect. Whatever the purpose, photo lighting filters are a useful photography tool and can be made at home.
Purchase several sheets of clear acetate. These are also called overhead projector transparencies.
Create multiple image files with swatches of color that match your desired filter colors. You can look at commercially available lighting filters to see the range of colors they use and copy them. Make each swatch as large as you would like the resultant filter to be. The easiest method is to create several 8-by-10-inch swatches of color that will fill an entire acetate sheet.
Use a professional printing service to print each swatch on one acetate sheet. If your swatches are small, you can print multiple on the same sheet.
Cut each acetate sheet to the size of your swatch so that there is no transparent film remaining.
Cover your flash bulb with one of your colored acetate sheets to create a photo lighting filter. The filters can be attached to a flash bulb or lamp with clear tape. The tape will adhere to the acetate but can be peeled off easily without leaving a residue. You can also use a commercially available gel holder.