Hi.I am aLeica and Rollei user from Hong Kong,and is a new commer in LF camera. Landscapes is my main interest,and wide angle lenes are my most frequently used lenes. I'm quite interested in the Schneider Super symmar XL lenes. But I don't understand why different focal length eg,80mm, 110mm, 210mm, can have same angle of coverage ie.105 degrees. And can the 210mm lenes be used on my 4x5 field camera ,like the Toyo? Thanks very much . From Joe.