If I had to narrow it down to one lens only, and could only carry one for the rest of my life, in my 4x5 cameras it would be my Rodenstock Grandagon 65mm (same as a 20mm on a digital full frame or 35mm camera). My second choice would be my 90mm Sinaron-S which is so sharp it's scary. On my Hasselblad it would be the 50mm which is the same as a 25 on most digital and 35mm cameras. There isn't a sharper lens, or one with better contrast characteristics than these lenses. German glass rocks!