No shadowing at 15-85 EF-S and as far as I can tell with the naked eye is the image quality even with the filter 1a. However, there is a serious drawback: Although the Canon lens cap fits just on it, but scratched with time the edge of the filter, which leads to visible sharpness waste. And at least in my polarizing filter, no extra lens cap was there, of which I have here indeed read in a comment, but never saw him ...