Does anyone know what the max number of times I can use a step up ring before I start to degrade image quality? I've got an Olympus epl5 with a 20mm pancake lens. Since getting rid of my DSLR I've got a 0.9nd filter that's 67mm but the pancake is 46mm I believe. I don't really want to get rid of the nd filter because it's quite nice Suggestions? Does anyone have experience with the adjustable nd filters?