The "IF" in Pentax DA★ 200mm f/2.8 ED (IF) SDM stands for "Internal Focus". I know what this means: the lens doesn't change in size as I focus. (And it's true; it doesn't.) What's the point of this, ...
The specification for the lens says that the Nikkor 18-105mm ED VR has the IF feature. However, the local market product label doesn't advertise this feature. How can I make sure that the IF feature ...