Which filter is used to decrease light intensity without changing its color?

A neutral density filter is specifically designed to reduce the intensity of light without altering its color. This is essential in various settings, especially in theatre and photography, to manage light levels while preserving the original hues of the lighting. By using this filter, artists can maintain color temperature and saturation, allowing for effective scene lighting adjustments without distortion.

In contrast, other options such as a luminaire typically refer to the light source itself and do not serve the purpose of filtering light. An overlay is usually associated with a technique or material placed on top of a surface, which may not inherently focus on light intensity reduction. A lantern, while it can emit light, does not function as a filter for light manipulation in the same way. Thus, the neutral density filter is the correct choice for achieving a decrease in light intensity without changing color.