Whether a product claiming to protect your camera's lens & screen reduces its overall quality depends on the product's and your application's quality. If you buy something cheap with poor building materials, you might see distortion in your image quality. In addition, if you do not place the protector correctly, it can lead to similar results. But many products offer supreme quality. They're made of high-quality materials giving HD imaging, bubble-free application, and superior clarity. So, ensure you buy the quality item and use it properly.