Why is it not possible to make a lens that does not attenuate light at all? As far as I know, there are no lenses available with max aperture < f1.4? What limits the creation of say a f0.5 lens for instance? BTW I just got the Sigma 150 macro and the Nikon 14-24 for use on D300. I hate to say it but the Sigma may actually be superior to my 105 VR micro lens. However I will never sell the 105 because that is such a great focal length. Can't wait to someday get a D3 for the 14-24, 24-70, and 105 VR for weddings and events etc. I am torn between getting a 200 f2 someday or acquiring a 70-200 if Nikon updates the lens.