Which statement is true about protecting the filter lens?

The correct statement emphasizes the importance of protecting the filter lens in photographic or optical equipment. Placing a clear glass lens in both front of and behind the filter lens provides a dual layer of protection. This is crucial because filter lenses can be susceptible to scratches, dust, and other environmental factors that can affect image quality. By having a clear glass lens in front, it acts as a first line of defense, while a second lens behind can help protect from any impacts or damage to the filter from the equipment side.

This approach not only helps in preserving the integrity of the filter lens itself but also enhances the lifespan of the overall optical setup. Therefore, using clear glass lenses in this manner is a practical and effective method to maintain equipment quality and ensure optimal functionality.