I bought 2 versions of the Xit - 52mm for my 40mm f/1.4 and 58mm for my 50mm f/2.8. The optics of these two nozzles are very similar, ie relatively poor. I've been a photographer for many years and I've gotten to the point where I'm tired of lugging around large and heavy lenses, especially when I'm on a hike. These days I mostly shoot with 50mm f/1.4 or 40mm f/2.8 lenses (aka "pancakes"). These fixed focal lengths are light, compact and offer incredibly good optics. However, their fixed medium