Technical Glossary
A lens in which you can adjust the focal length is called a zoom or a zoom lens. The advantage of a zoom lens is that the frame can be varied without changing your location as the photographer. Zoom lenses have become indispensable. Tamron has achieved an image performance in its zoom lenses which comes close to those of fixed focal length lenses through its ongoing efforts in research and development (e.g., LD - AD - as well as aspherical elements).
The zoom lock (
ZL) mechanism is an extremely useful and much appreciated mechanical concept developed by TAMRON. This feature prevents undesired extension (creep) of the lens barrel when carrying the camera/lens unit on a neck strap. This enhances responsiveness in the field and helps protect the lens.
Lenses with zoom lock (
ZL) function: 
Di III Lenses
Di II Lenses
SP AF 17-50mm F/2,8
VC
XR
Di II
LD Aspherical [
IF]
SP AF 17-50mm F/2,8
XR
Di II
LD Aspherical [
IF]
AF 18-200mm F/3,5-6,3
XR
Di II
LD Aspherical [
IF] MACRO
18-270mm F/3,5 -6,3
Di II
VC
PZD
Di Lenses
SP AF 28-75mm F/2,8
XR
Di
LD Aspherical [
IF] MACROsingle
AF 28-300mm F/3,5-6,3
XR
Di
LD Aspherical [
IF] MACRO
AF 28-300mm F/3,5-6,3
XR
Di
VC
LD Aspherical [
IF] MACRO
SP AF 200-500mm F/5-6,3
Di
LD [
IF]
