pop said:today i learn some new things, which is good.
btw, the issue of vignetting, is poor lighting a possible cause? when i took the 3 shots above, although it is next to the window, the weather has been overcast today, so lighting may not be adequate?
yes yes we should be prepared to learn something new everyday.
vignetting has to do with the lens at that particular focal length (sorry I can't really explain, you could do a google) and not due to your photographic skills.