Tamron is a Japanese based lens maker founded in the 1950's, which made its early reputation on Adaptall lenses (lenses that could be adapted to different mounts) and then later the first superzoom lens for film SLRs (the 28-200mm f/3.8-5.6 in 1992).
Tamron is not a huge company (only 6000 employees), and basically only makes optics (lenses for consumer cameras and commercial products).
Tamron terminology used in their product descriptions:
- AD: Anomalous Dispersion optical element
- ASL: Hybrid Aspherical optical element; compensates for spherical aberration
- BBAR: Broad-Band Anti-Reflection coating; increases contrast, reduces flare and ghosts
- IF: Internal Focusing; front element not involved in focus
- LD: Low Dispersion optical element; reduces chromatic aberration
- PZD: Piezo Drive autofocus motors; internal lens motors
- SP: Super Performance (marketing term for higher performance lenses)
- USD: Ultrasonic Silent Drive; autofocus motor that is quiet
- VC: Vibration Compensation system; compensates for camera movement
- XLD: Extra Low Dispersion optical element; reduces chromatic aberration
- XR: Extra Refraction optical element; bends light at steeper angles
- ZL: Zoom Lock; locks the zoom mechanism of the lens
Also, Tamron has three confusing line designations: