|
Canon EF-M 15-45mm f/3.5-6.3 STM IS - Review / Test - Analysis |
|
Lens Reviews -
Canon EOS (APS-C)
|
|
Page 2 of 2
Distortion
Many mirrorless lenses rely on digital auto-correction here but fortunately, Canon follows a more conservative approach.
The Canon EF-M 15-45mm f/3.5-6.3 STM IS produces a strong degree of barrel distortion at 15mm but at ~3.3% this is still
moderate compared to what we've seen elsewhere in the mirrorless lens segment (Hello Fuji & MFT?). The distortions
are equalized at 28mm followed by a moderate barrel distortion (1%) at 45mm. The latter is a little bit unusual actually - pincushion
distortion is much more common at the long end of the zoom range.
Vignetting
Unfortunately vignetting is a massive weakness - again. We have seen this problem in our previous EF-M reviews
so by now we are pretty confident to state that this isn't solely a lens issue. It seems as if Canon
just took their APS-C sensor developed for some of their DSLRs and this just wasn't the smartest thing to do due
to much closer distance to the lens' rear element. It seems as if the sensor doesn't like the more extreme light
angles towards the corners.
The "raw" light falloff is shockingly high. At 15mm @ f.3.5, the Canon lens holds the new negative record (again)
with a whopping 3.6EV(!!!). This is more than double our usual scale for APS-C format lenses!
Even at f/11, you can observe a falloff of ~1.4EV (f-stops). The situation isn't quite as bad at 28mm where f/5.6
is sufficient to solve most of the issue. At 45mm it isn't overly relevant anymore.
Consequently, you should leave the vignetting auto-correction activated although you'll have to live
with increased corner noise at the wide-end in this case.
MTF (resolution)
The resolution figures of the Canon EF-M 15-45mm f/3.5-6.3 STM IS are quite decent.
The weakest spot is at 15mm @ f/3.5. While the centre quality is great, the outer image field
is soft. However, stopping down to f/5.6-8 boosts the sharpness to a very good quality across the image field.
The centre quality decreases gradually towards the long end of the zoom range but the corners are
quite good even at max. aperture. Diffraction has a limiting effect from f/11 onward.
The centering quality of the tested sample was Okay (albeit not great)
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 (CAs)
The amount of lateral CAs is very moderate with an average CA pixel width at the
image borders around the 1px mark.
CAs are usually taken care of by the camera's auto-correction or
in various RAW converters (Canon DPP, Adobe Photoshop, etc) so there's little to worry about here anyway.
CA auto-correction is a lossless procedure.
Verdict
The Canon EF-M 15-45mm f/3.5-6.3 STM IS may not be their most glorious offering but it is actually a quite
decent lens. Unless we are talking about the wide-open performance at 15mm, it is a quite sharp lens. Image distortions, as well as lateral CAs, are
about average for a lens in this class. There's one substantial weakness - the dramatic vignetting at 15mm although most of the issue does probably
originate in the image sensor rather than the lens. In any case, it's a good idea to leave image auto-correction activated here.
The build quality of this retractable, tiny lens is nothing to rave about but still livable. If you don't like plastics this one is not for you though.
The auto-focus relies on Canon's noiseless STM (Stepping Motor) which also operates reasonably fast albeit not class-leading. Please note that the AF speed
is also related to the performance of the camera so it may and it will improve with the next camera generations. The image stabilizer is certainly a very
valuable feature given the fact that the lens is very slow especially at its 45mm setting.
The Canon EF-M 15-45mm f/3.5-6.3 STM IS competes against its in-house mate, the Canon EF-M 18-55mm f/3.5-5.6 STM IS. The EF-M 18-55mm
has a better build quality but optically the two are fairly similar. Thus if you have the choice between the two it comes down to your preferences
regarding range and construction quality.
|
to 