This tutorial is written with the assumption that you have already completed and understand the Beginner
Tutorials under Help > Beginner Tutorials or in Chapter 3 of the User’s Guide. This tutorial does not
therefore repeat all of the basic information about how to start a project, setup the analysis, run the
raytrace and view the results. If you have not yet completed the Beginner Tutorials, then please do so
before you proceed.
This project will create an open 4-lamp T8 fluorescent luminaire with a reflector that produces a mediumwide
beam with a spacing criterion (S.C.) between 1.3 and 1.5. S.C. is the ratio of the spacing to the
mounting height at which the illuminance half way between two luminaires equals the value directly
underneath the luminaire. It therefore indicates the spacing that is achievable while maintaining relatively
1. Start Photopia and create a new project and save it as 4 Lamp 18W Strip Light.ray.
2. This project will be done in mm, so make sure the project units are set to mm. This is indicated
next to the coordinate readout in the lower left corner of the screen. You can change the units
under File > Preferences or by typing the UNITS command.
3. The luminaire is to be 600 mm long, so import an 18W tubular fluorescent lamp using File >
Import Lamp. Choose the lamp model named F18-33. The complete list of lamps is found under
the Library > Lamp List menu. Insert the lamp at 0,0,0.
4. Go to front view. Your CAD view should look like the following image.