The use of 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 protective layer 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 splashing water. 2. Reduction of 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, haze and loss of contrast in images. By absorbing the UV light, the UV filter can help achieve clearer and higher-contrast image quality. 3. Easier to clean: A UV filter is easy to clean and replace. In the event of contamination or damage to the filter, there is no need to clean or replace the entire lens. 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 damaging the objective lens. It's 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 impairments in image quality. I use it with a 49mm diameter on the Pentax Limited HD Macro lens with a 35mm focal length, which itself has multi-coated lenses, and I was curious to see whether the coating of the very inexpensive filter and the HD coating of the Pentax Limited “get along” with each other this seems to be a good marriage. The protection of the front lens is also very important to me, because with this macro lens in particular you sometimes get to the subject itself with the lens, which is not good if it is very hard. Ultimately, the use of a UV filter in front of a lens depends on personal preferences, requirements and shooting conditions anyway. Some photographers prefer to always use a UV filter to protect their lenses, while others choose not to 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 also not a problem with the K&F Concept filter, because the thread is milled to fit and precisely, so that it can be screwed on and off very easily. The built-in stray light filter and the dust protection cap of the Limited can also be used without any problems. So far I can recommend the filter unreservedly. If I see anything negative, I'll update the review.