Canon EF-S 18-55mm f/3.5-5.6 STM IS - Review / Test Report - Analysis
Lens Reviews -
Canon EOS (APS-C)
Page 2 of 3
The EF-S 18-55mm produces a heavy degree of barrel distortion at 18mm (~3.2%) but this is quite normal for such lenses. The issue is significantly reduced at 24mm (~0.8%) and pretty much negligible at 35mm/55mm.
Move the mouse cursor over the focal length text marks below to observe the respective distortion
The optimization of the light falloff was obviously not a primary design objective. As always, the worst vignetting is at the wide-end with a rather extreme and easy visible vignetting of ~1.8EV at f/3.5. This is actually off our standard scale. The vignetting improves at f/5.6 but it takes f/8 till the problem is more or less resolved. The other focal lengths are not as affected but you should still reckon with about 1EV of vignetting at 24mm and 35mm at max. aperture.
Most readers will probably look at the MTF/resolution charts in disbelief - and honestly so did we although the predecessor was impressive in this respect as well. The results are great and that's throughout the focal length range and at all relevant aperture settings. There is a bit of field curvature (curve focus field) but it's not excessive.
The centering quality of the tested sample was quite decent.
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
Chromatic Aberrations (CAs)
The level of lateral CAs (color shadows at harsh contrast transitions) is generally very well controlled with an average pixel width around 1px at the extreme ends and somewhat less in the middle range.
The above chart illustrates the state at the image borders which is at ~3/4 of the distance from the center to the very corners. However, it is worth mentioning that the issue worsens significantly at 18mm when looking beyond - we measured a CA pixel width of 2.5-3px in the very corners so it is advisable to take counter-measurements (e.g. via a RAW converter) to correct the issue.