About a month or two ago someone tried to take some photographs through their truck window of a landscape image (pond, birds) and wondered why the camera couldn't focus and the image was fuzzy. While taking some baseball photos I walked past a Window and decided to try to shoot through the window just for fun. The Nikon D500 has an awful problem trying to focus. So I manually focused and got a better shot than the camera's AF would have done. But still, you can tell the difference in detail/IQ between which one was and wasn't shot through a window. Of course I knew looking through the window with my own eyes that there was a difference. Thus when people ask about their filters I mention to put it up against a book/newspaper and compare the image before and after. These example will show you the loss in IQ. Keep in mind I *had* to manually focus the shot through the window for the best image vs the camera's which was a lot more OOF. SOOC - D600 JPEG set to Vivid.