A system of modular multi-aperture reflector sheets for use in general and specialty luminaires is disclosed. These sheets, designed to be simple in design, manufacture, and installation, allows for enhancing, adjusting, varying, or correction of the light distribution provided by luminaires during production or deployment. The reflector sheets are made of highly-reflective, thin material and feature multiple apertures that are patterned to redirect the light output emerging from the output of a luminaire. The reflector sheets are intended to be used in combination with both standard and custom reflectors and replace complicated and expensive lenses and optics that are often deployed to modify luminaire light distribution. The sheets are modular and can be replaced easily, allowing for standard luminaires having multiple possible light distribution patterns without further complication. Also, custom multi-aperture reflector sheets can be designed, shipped, and installed easily if further modification or correction of the light distribution is desired.