Probably a fundamental question since I know next to nothing...

[Viper GTS]

I have a D70S and I've got two lenses here for it. One is a Tamron 18-200 DiII (f/3.5-6.3), the other is a just out of the box Nikon 55-200 VR (f/4-5.6).

The Tamron will focus fine at full zoom on objects that are very close (on my desk). The new Nikon will not focus at any zoom level. In manual mode it's obvious that it simply can't do it (from lock to lock nothing is in focus). If I try something that is a few feet away it works great.

Why is this?

Viper GTS

 

[fuzzybabybunny]

Some lenses are just designed differently. Your Tamron seems to be the AF18-200mm F/3.5-6.3 XR Di-II LD Aspherical (IF) Macro. It was specifically designed to have light macro capabilities, which include being able to focus closer than comparable lenses in its class. Seems like your Tamron's minimum focusing distance is 17.7in. (0.45m) while the Nikon's is around 3.1ft, which means an object has to be at least 17.1in away for the Tamron to focus on it while an object needs to be at least 3.1ft away for the Nikon to focus on it.

The minimum focusing distance tends to increase as you zoom out more. That 3.1ft away for your Nikon might only be at the 55mm end. At 200mm it will likely be even longer.

 

[Viper GTS]

Interesting. So I guess I'm not selling the Tamron after all...

Viper GTS