I just got this lens and after reading some materials online I have more questions now than before. When using macro with digital, the camera compensates for light fall off by changing the aperture. What happens with this lens? I read somewhere that the P lenses have compensating aperture when focused to 1:1. Is that the case? I also read somewhere that this lens doesn't do 1:1, but it is clearly marked on the barrel 1:1. Any help here?