i assume you mean "DX" lens, not "G" lens, G means it's a aperture ring less design. which has nothing to do with the vignetting effect.
Both the Sigma 18-50 and Nikon 17-55 lenses are designed for APS-C sensor camera only so both of them will have severe vignetting problem when used on full frame camera.
On the other hand, if you have a old film camera, then you don't want the G lens as those cameras require a mechanical aperture ring on the lens to set the aperture.作者: 卡洛斯 时间: 2010-5-22 18:36:46