They both appear to be the same, except the Xenar is slightly larger physically. Without having both in hand at the same time, I cannot be sure. I own the Tessar, and I have an opportunity to own the Xenar that's attached to a camera I want to purchase. I may be able to work out something where I don't have to take the lens. However, the cost differential isn't that much. I found information on the Xenar, but not the Tessar. Is there a difference in image circle at all? Does anyone have any specs on the Tessar? The one thing I can say from experience....it ain't got a heck of a lot of spare image circle for movements. Maybe an inch either way. But it gives a lovely image. Will the Xenar give a bigger image circle?