hope this is not too silly a question. I have a tamron 17-50 2.8; was thinking of getting a hoya +4 close up. However, my closest focusing distance is already...0.27m if i'm not wrong. So with a +4 my focusing distance will become 0.25m. Am I right to say that essentially there is no point getting a close up filter +4 or less? Because the magnification ultimately is due to the lens zoom and the filter only allows me to focus closer?