Originally posted by weaponx525 Would the equivalent field of view be 32-160 if I use the 28-105 on my K5 I and the 16-85 would "become" 24-127?
Essentially yes. Used on APS-C, a 28~105mm zoom would give the equivalent of about 32~160mm on a FF. The 16~85mm mounted on FF
used in crop mode would provide the equivalent of 24~127mm on FF
used in FF mode. PLEASE NOTE THAT, when the 16~85mm is mounted on an APS-C camera, the coverage is the same as a 24~127mm mounted on a FF camera
in FF mode. AT THE PRESENT TIME there is no K-mount lens capable of covering a FF sensor that will give the same zoom range that the 16~85mm provides on APS-C. But in fairness, that applies to many APS-C zoom lenses, almost too many to list (10-17 fish-eye; 20~40; 17~70; 18~135/250/270/300; 50~135; 55~300 - - and there are more). It is easier to make a satisfactory long-range zoom for a smaller sensor than for a FF sensor. Part of the problem can be seen by comparing the APS-C 16~50 to the FF 24~75. These lenses have the same angular coverage on their respective sensor size, but the 24~70 is much bigger, heavier, and more expensive.