Which filter is primarily used to reduce the amount of light entering the camera without changing color?

The ND (Neutral Density) filter is specifically designed to reduce the intensity of light entering the camera without altering the colors in the scene. This is particularly useful in bright conditions where filmmakers want to maintain a shallow depth of field or achieve slower shutter speeds for creative effects, such as motion blur, while keeping the exposure balanced. The ND filter allows for greater flexibility in adjusting the camera settings, permitting filmmakers to work with the desired aperture and shutter speed settings even in very bright situations.

In contrast, a graded filter has a gradient that can darken certain parts of an image, typically the sky, and alter color perception. A polarizing filter is used to reduce reflections and enhance contrast, specifically affecting color saturation and clarity, which is not the primary function of an ND filter. A color filter is designed to change the overall color balance of the image, making it unsuitable for the purpose of reducing light without affecting color. Thus, the ND filter stands out as the ideal choice for reducing light intensity while keeping color fidelity intact.