How far does the the flagship Tamron 18-270mm f/3.5-6.3 DI-II (IF) LD VC Macro Aspherical lens build on the promise of the earlier 18-250mm model, and does it make the extra £100 a worthwhile investment?
The 18-270mm lens is longer, wider, heavier, more expensive and features more elements. These are not, however, necessarily bad things: the wider barrel is easier to grip and its greater length means the zoom ring has almost the same wideness as the zoom and focus rings combined on the older lens. The zoom action has a slight hesitation around 70-100mm, but this is minor and does not detract from its overall smoothness.
The Vibration Compensation system, which takes a moment to activate, does an excellent job of steadying the viewfinder image and is probably the best reason to prefer this lens over the 250mm version. Sadly, the higher-technology lens is available in Canon and Nikon fits only, whereas its ancestor is also available in Pentax and Sony mounts.
As was the case for the 250mm version, the MTF curves again show a distinct separation between the longer and shorter focal lengths. The differences are not quite as acute due to both some improvement at the longer focal-lengths and a little mid-range degradation. That said, there is a significant improvement in wide-aperture performance generally and the minimum focal-length MTF curve is much better than before. Nevertheless, there is no escaping the fact that Tamron still has some work to do in respect of the longer focal lengths’ MTF figures.
Chromatic aberration was seen, especially at the maximum focal length, in both the technical images and also demanding real-world pictures, such as along the edges of the distant blocks of flats in the standard test scene. Ironically, it was probably the greater sharpness provided by the activated vibration compensation system that allowed the fringes to be seen in all their glory.