Canon EF 20-35mm f/2.8L - Review / Lab Test Report - Analysis
Lens Reviews - Canon EOS (APS-C)
Article Index
Introduction
Analysis

Distortion

Typical for many ultra-wide lenses the EF 20-35mm f/2.8 L suffers from pronounced barrel distortion (1.8%) at the wide end of the zoom range. The situation eases towards the 35mm setting where the lens shows a marginal degree of barrel distortion.

20mm:

24mm:

35mm:

The chart above has a real-world size of about 120x80cm.

Vignetting

As mentioned above the Canon lens is a full frame lens so on APS-C it can take advantage of the sweet spot effect. As a consequence vignetting is low even at wide-open aperture. At f/4 the issue is absolutely negligible.

MTF (resolution)

In the lab the oldie showed that it's not ready yet for retirement. The center resolution is excellent throughout the zoom range. The borders are only good at f/2.8 but the quality increases rapidly towards medium apertures where it hits very good to sometime excellent levels.

This sounds very promising but it is worth to notice that it was a little difficult to do the MTF tests because the lens suffered from a quite pronounced field curvature. For most applications field curvature is no issue but you should stop down if you intend to shoot flat objects at close focus distances.

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 (CAs)

Chromatic aberrations (color shadows at harsh contrast transitions) are very pronounced with this lens peaking in the average CA pixel width of ~1.3 pixels at the image borders. Not impressive but this is quite typical for zoom lenses of this range.

Verdict

The Canon EF 20-35mm f/2.8 L may be old, even ancient by consumer electronics standards but it's still capable to deliver high quality images specifically regarding resolution and low vignetting (on APS-C DSLRs) whereas distortions, field curvature and CAs are a little on the high side. Thanks to L-grade build quality it feels very solid but expect that time has taken its toll from a ~15 years old lens. If you can find a sample in decent condition it is still worth a deeper look but remember that it is probably beyond repair in case of malfunctions due to rare spare parts.

Optical Quality:    
Mechanical Quality:
Price/Performance:discontinued
      
   What does this mean ?



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