has any one had any experience with the wollensak velostigmat? this lens has a 9 1/2 inch focal range, to be used on 8*10. the outer, foremost, element rotates 360, and it is marked in five settings. it is coated. it is mounted in a Betax N o. 4 shutter. the barrel is about 2 1/2 inches in diameter which means it is hea vy. it is calibrated from 4.5 to 64. i'd like to know what subject matter this l ens was built for, and how does one use the rotating outter element? thanks.