Sigma AF 70-300mm f/4-5.6 DG APO macro - Review / Test Report - Analysis
Lens Reviews - Canon EOS (APS-C)

Distortion

The level of distortion is low throughout the range starting with negligible barrel distortion at 70mm changing to medium and slight pincushion distortion at 200mm and 300mm respectively. Pretty decent for a 4x zoom lens.

70mm:

200mm:

300mm:

The chart above has a real-world size of about 120x80cm. Possibly expect more distortion towards closer focus distances.

Vignetting

The Sigma is a full frame lens so it enjoys the usual sweet spot advantage on APS-C DSLRs. At wide open aperture the vignetting is around 0.5EV which is normally not objectionable. As usual it helps to reduce the issue by stopping down a little.

MTF (resolution)

The lens exhibited a quite mixed performance regarding resolution. At 70mm the quality is on a very high level which is even rivaling fix focals in this range (but much slower). At 200mm and 300mm the center performance remains on a very good level but the border quality starts to suffer here. At 200mm it helps to stop down a little but at 300mm the border quality is dismal at f/5.6 and it doesn't really recover a little till f/11.

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

The lens produced a varying degree of chromatic aberrations (color shadows at harsh contrast transitions) at the image borders. At 70mm the issue is basically non-existent and at 200mm it's still quite well controlled. However, at 300mm the problem exceeds 1.5 pixels which is rather critical. Please note that CAs can be (auto-)corrected via imaging tools.




© by photozone.de