it depends on what you mean by 'quality'. Sometimes companies like canon make a special high grade set of lenses (in canon's case it's their 'L' series), which are very high quality in most every respect - from autofocus to build to optics. Some digital grade lenses have those aspects, but they rarely have all three simply because they can't be used on all professional cameras (like canon's 1d cams), and companies feel that consumers that own cropped cameras wouldn't spend the high amount of money on super nice lenses. if they would, they would likely have a pro camera also. There are some digital lenses that are very high quality, like the sigma 30mm 1.4, the canon 17-55 2.8 IS, and a few others. It's very relative, their isn't major split between the two. However, 'digital lenses' do have a reduced image circle, so they have worse vignetting wide open.