In my copy of "The Photoshop Lightroom Workbook" (for LR2) by Seth Resnick and Jamie Spritzer, they say on the subject of "Filters" - "While many photographers used all kinds of filters with film-based cameras, it is generally not a good idea to use them with digital." They go on to say that, "light will pass through the filter , hit the sensor and then reflect back on the sensor instead of passing through the filter. Skylight and UV filters are also altering the wavelength of light that hits your sensor." In a way, that makes sense, but then ... why do manufacturers of lenses for digital cameras provide the threads to mount filters? I always kept a filter on my film cameras, I have a UV filter on my Nikon prime lens, and a polarizing one on my Nikon telephoto. I bought filters for my M43 lenses, but now am reluctant to mount them on the lenses. I don't know if these authors held to their opinions in later editions, but I wondered what people have experienced in the real world. Is it that BIG an effect? Do filters reduce contrast? Do they cause reflections? Or, do they improve the image?