Tamron 18-200mm F/3.5-6.3 Di III VC NEX Lens

Tamron 18-200mm F/3.5-6.3 Di III VC Performance

As is typical for high ratio zooms like this, sharpness at shorter focal lengths is excellent, with performance dropping off as the lens is zoomed in.

At 18mm, clarity in the centre of the image is already outstanding at maximum aperture, with very good sharpness towards the edges of the frame. Peak sharpness is achieved between f/5.6 and f/8 where clarity is excellent across the frame.

Zooming to 70mm results in reduced sharpness in the centre although it still reaches excellent levels between f/5.6 and f/8 and the clarity produced towards the edges is still very good.

Finally at 200mm, sharpness in the centre is reduced again, but still remains very good, unfortunately as you get closer to the edges of the frame clarity is reduced to fairly good levels. Peak quality across the frame is achieved at f/11 for this focal length where sharpness in the centre is very good in the centre and good towards the edges.

MTF @ 18mm

MTF @ 70mm

MTF @ 200mm

How to read our charts The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. Averaging them out gives the red weighted column. The scale on the left side is an indication of actual image resolution. The taller the column, the better the lens performance. Simple. For this review, the lens was tested on a Sony NEX-3 using Imatest.

At shorter focal lengths, chromatic aberrations are extremely well controlled. Fringing does increase as the lens is zoomed in and chromatic aberrations are at their strongest at 200mm. Here levels of fringing can exceed one pixel width towards the edges of the frame, which may become visible along high contrast edges, and especially in large prints.

Chromatic aberration @ 18mm

Chromatic aberration @ 70mm

Chromatic aberration @ 200mm

How to read our charts Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software. Apochromatic lenses have special lens elements (aspheric, extra-low dispersion etc) to minimize the problem, hence they usually cost more. For this review, the lens was tested on a Sony NEX-3 using Imatest.

Falloff of illumination towards the corners of the frame is very well controlled with the corners being 0.9 stops at 18mm and 0.7 stops at 200mm darker than the image centre. Visually uniform illumination across the frame is achieved with the lens stopped down by one stop throughout the zoom range.

Imatest recorded a level of 5.03% barrel distortion at 18mm, which is reasonable for a lens of this type, but may still pose issues when shooting subjects like architecture where straight lines are important. At 200mm this barrel distortion is replaced with a low level of 0.305% pincushion distortion. The distortion pattern remains even across the frame, so should be relatively easy to correct in image editing software afterwards.

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