Certified Professional Photographer (CPP) Practice Exam 2026 - Free CPP Practice Questions and Study Guide

A neutral density (ND) filter is designed to absorb an equal quantity of all wavelengths of light that pass through it, making it effective at reducing the overall intensity of light without altering the color balance of the scene. This quality allows photographers to achieve desired exposure settings in bright conditions, or to use wider apertures or slower shutter speeds that would not be possible without the filter.

This ability to uniformly dim the light can be particularly advantageous when capturing images that require longer exposure times, such as for creating motion blur in flowing water or for achieving a shallow depth of field in bright sunlight. This function directly ties to the definition of a neutral density filter and is fundamental to its application in photography.

The other options highlight effects and features that are not directly associated with the core function of a neutral density filter. For example, increasing color saturation or enhancing contrast are not achieved through the use of neutral density filters, nor do they absorb light equally across the spectrum. Additionally, while some filters may help reduce lens flare incidentally, that is not the primary function of a neutral density filter.