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Tamron 10-24mm f/3.5-4.5 Di II VC HLD (Canon EF) - Review / Test Report - Analysis |
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Lens Reviews -
Canon EOS (APS-C)
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Page 2 of 3
Distortion
You are never going to win a flower pot with ultra-wide zoom lenses when it comes to image distortions. However, compared to some of its mirrorless cousins, the Tamron isn't terrible in this respect at least. Unsurprisingly, there is a heavy barrel distortion (3.3%) at 10mm. The distortions ease rapidly when zooming out a little and the issue is negligible at 14mm. At "longer" focal lengths, pincushion-style distortions take over but they remain on a slight level.
Needless to say but nowadays it's usually possible to correct such issues via lens profiles in your favorite RAW converter. This procedure is a bit lossy in terms of image quality though.
Vignetting
Compared to full cameras, vignetting is a harmless topic in the APS-C world. That being said - within the APS-C scope, the Tamron has its fair amount of issues here. The light falloff is worst (1.4 EV) at 10mm f/3.5 and around the 1 EV (f-stop) mark at other focal lengths at maximum aperture. Stopping down helps to reduce the vignetting but traces remain even at f/8 especially at the wide end.
Please note that there are also limits here due to the amount of "natural vignetting" that is always present at such wide focal lengths.
MTF (resolution)
The resolution characteristic of the Tamron 10-24mm f/3.5-4.5 Di II VC HLD is ... sub-average. There's nothing wrong with the center resolution which is on a very good to excellent level across the zoom range at relevant aperture settings. However, the same can't be said about the outer image field. Formally the situation isn't too bad at 10mm at least. At maximum aperture the borders are good and only the extreme corners are soft. Stopping down solves the corner issues. Unfortunately, the 10mm setting is affected by heavy field curvature (see the next chapter). 14mm is clearly the sweet spot of the lens. The quality isn't stellar but generally very decent even at f/4. Beyond 14mm, the resolution tanks with very soft corners/borders. Stopping down to f/5.6 helps a bit but better stick to around f/8 for best results.
The centering quality of the tested sample was good.
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
Field Curvature
As already mentioned, field curvature is an issue at the wide-end of the zoom range. For the MTF section, we are refocusing per "local spot" (center, border, corner). Normally, this is not an issue because the variations in focus distance are mild and not overly relevant in real life. However, there are exceptions to this and the Tamron lens is clearly one of them. Just to illustrate the degree of the issue, we extracted the "flat field" results at 10mm below. If you compare this chart to the 10mm chart in the MTF section, you can easily spot the difference. At f/3.5 the result is pathetic. The depth-of-field is catching up when stopping down so the field curvature is slowly "compensated". At f/5.6 the outer image field is at least not terrible anymore and decent quality is possible at f/8.
Please keep in mind that unless it's a hobby of yours to take pictures of walls at fairly short distances, the world is more of a three-dimensional place so in real life the borders/corners aren't as bad as this chart suggests (which is why we are usually not providing this analysis - it's usually just misleading).
Chromatic Aberrations (CAs)
Lateral CAs (color shadows at the image borders) are generally on a medium level at the image borders. They are quite decent at 10mm but strangely they peak at the 18mm setting - thus in the middle range - which is a bit unusual. An average CA pixel width of 1.8px is quite noticeable here.
That being said, the chart illustrates the CA at the image borders - but the issue is getting amplified in the extreme corners. You will be able to spot this in our sample image section as well but below is a 100% crop from our test charts taken at 10mm.
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