Using such a UV filter in front of a lens for mirrorless system cameras or DSLR cameras offers several advantages: 1. Protection of the front lens: A UV filter serves as an additional layer of protection for the front lens of the lens. It can help keep scratches, dirt, dust and fingerprints away from the actual lens. This protects the lens from damage, which is particularly advantageous in environments with adverse conditions such as sand, dust or splash water. 2. Reducing UV light: Although modern lenses already have a built-in UV coating, a UV filter can provide additional protection by blocking ultraviolet light. UV light can cause blurring, hazing and loss of contrast in images. By absorbing UV light, the UV filter can help produce clearer and higher contrast image quality. 3. Easier to clean: A UV filter is easy to clean and replace. If the filter becomes dirty or damaged, the entire lens does not need to be cleaned or replaced. That saves time and money. 4. Reduced risk of lens breakage: In the event of an accident or fall, a UV filter can absorb the impact, reducing the risk of damage to the objective lens. It is easier and cheaper to replace a broken filter than a damaged lens. However, using a UV filter can also have potential disadvantages. An inferior or poorly designed filter can degrade image quality by causing unwanted reflections, ghosting, or vignetting. Therefore, it is advisable to choose high-quality UV filters from reputable manufacturers to maintain the best possible image quality. The K&F Concept Filter from the K series is very inexpensive, but so far I have not noticed any impairment of the image quality. I use it with a diameter of 49mm on the Pentax Limited HD Macro lens with 35mm focal length, which itself has multi-coated lenses, and was curious to see whether the coating of the very inexpensive filter and the HD coating of the Pentax Limited “get along”, but this seems like a good wedding. Protecting the front lens is particularly important to me, because with this macro lens in particular you can sometimes reach the subject itself with the lens, which is not good if it is very hard. Ultimately, using a UV filter in front of a lens depends on personal preferences, requirements and shooting conditions. Some photographers prefer to always use a UV filter to protect their lenses, while others forego it in certain situations in order to achieve the best possible image quality. I myself am more of a mixture of these two types, because if I think it fits better without a filter, I simply unscrew it, which is no problem with the K&F Concept filter, because the thread is milled to fit and precisely, so that it can be screwed on and unscrewed very easily. The Limited's built-in scattered light filter and dust protection cap can also be used without any problems. So far I can recommend the filter without reservation. If I notice anything negative, I will add it to the review.