|
Sigma AF 70-300mm f/4-5.6 DG APO macro - Review / Test Report - Analysis |
|
Lens Reviews -
Canon EOS (APS-C)
|
|
Page 2 of 3
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.
Please note that the MTF results are not directly comparable across the different systems!
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.
|
