The Tamron SP AF 17-50mm F/2,8 XR Di II LD Aspherical [IF] is a light weight fast zoom that can be taken as an economic option instead buying genuine lens as Nikon or Canon; its main competitors are the Nikkor 17-55 F:2,8 DX AFS-G and the Canon EF 17-40mm f/4L USM. Is a lens to fit the APS-C format and you can not use it in FF cameras as the Canon 5D or EOS 1D. On the other hand, it can be used in the Nikon D3, although is a FF camera, DX lens can be used with FF sensor limitations. But it can not be used with the Nikon D40 or D40DX because it has not built-in focus motor, and this is a classical AF drive. The Tamron´s optical quality is really highy, and optically speaking, nothing to miss with its competitors , but the build quality, Nikon and Canon are better. This lens is made for Nikon, Canon and Sony mounts.

Its a 16 elements and 13 groups lens, including LD (low dispersion) elements , that helps to improve resolution and contrast.The minimum focus distance is 0,27 meters and weights about 434 gr.It has 7 rounded aperture baldes and 67mm filter diameter.; Petal Shaped hood included.

The optical and mechanical quality of this lens is very good, and it can be considered as a very serious altertative to the genuine lens.The color quality is surprisingly high, and its suffers for the classical 17mm distortion, at 24mm and beyond the distortion is minimum. The Tamron is an APS-C lens with smaller image circle, so vigneting is clearly visible at fast apertures.

Tamron resolution is good to excelent, even at corners, where another lens has its weak point.

The test was made with a Din A3 ISO 12233 chart and a Nikon D200 with tripod and a MC-30 cable release. In the Nikon´s settings the sharpness was high, and sensibiity 100 ISO , natural light, and the levels were balanced in Photoshop , and was saved as jpeg, maximun quality. Focus techniques has not been used in this test. It must be understood that jpeg compresion afects lightly the image quality.