Tamron AF 70-200mm f/2.8 SP Di LD [IF] macro - Full Format Review / Lab Test - Analysis
Lens Reviews - Canon EOS (Full Format)

Distortion

The Tamron SP lens produces a moderate amount of barrel distortion at 70mm and moderate pincushion distortion in the middle to upper zoom range (note: the analysis software reported fairly low distortion at 135mm but visually it looks "moderate" rather than "marginal" here). You may notice that the tested sample reported "188mm" at its 200mm setting. It is not clear whether this is typical for the design or a zoom limiter which set in too early on this copy/instance of the lens.

Move the mouse cursor over the focal length text marks below to observe the respective distortion
70mm 135mm 200mm

Vignetting

Vignetting is a critical topic for most lenses when used on full format DSLRs but it's not an overly significant issue on the Tamron lens. The problem is, of course, still visible at 1.3/1.4EV at max. aperture and 135mm/200mm but it remains comparatively moderate. It is usually sufficient to stop down to f/4 to solve the issue and it's technically negligible from f/5.6 onwards.

MTF (resolution)

The Tamron lens delivered a solid performance is our MTF lab. The center performance is generally nothing to worry about - it is already very good at f/2.8 and excellent in the f/4-f/8 range. The border and corner performance is also on a very high level at 70mm but there's a more pronounced drop down to about good+ results at 135mm and 200mm.

The amount of field curvature is marginal. While not formally tested it was quite obvious that the performance decreases towards very close focus distances at the long end of the zoom range. The tested sample showed a very slight centering defect at 200mm @ f/2.8.

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations

Lateral CAs are generally very well controlled - the LD elements used in the optical design seem to be pretty effective reducing this aberration. An average CA width of ~1px or less at the image borders it is usually nothing to worry about in field conditions.

Bokeh

Fast tele zoom lenses should be able to provide a pleasing bokeh (out-of-focus blur) for typical shallow depth-of-field applications such as portraits. Typical for such lenses it is capable of producing circular out-of-focus highlights in the center zone but they're deteriorating to a "cat's eye" towards the borders due to vignetting effects at f/2.8. Stopping down recovers the cat's eye towards a circular shape in the outer image portions. The inner highlight discs are smoothly rendered. The background and foreground blur is very smooth whereas the critical focus transition zones is a little more nervous. All-in-all a very good characteristic here.

These sample portions were taken at ~135mm.

Bokeh Fringing / Longitudinal Chromatic Aberrations (LoCA)

Bokeh fringing is a color fringing effect in the focus transition zone showing a purple halo in front of the focus zone and a green one beyond. The Tamron lens has a rather typical characteristic here with a medium degree of LoCAs at f/2.8. The effect is mostly gone at f/4 and basically negligible at f/5.6. The aspect is more pronounced at 200mm - the sample crops below were taken at 135mm.

Move the mouse cursor over the f-stop marks below to observe the respective LoCAs
f/2.8 f/4 f/5.6




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