Optical limits previously reviewed the Tamron 35mm which you can read about it here. You can also read the full 20mm review here and the 24mm review here, or you can see the summary below:
Tamron 20mm F/2.8 Di III OSD M1:2
The Tamron 20mm f/2.8 Di III OSD M1:2 is a bit of a complicated being. Obviously, it’s not meant to be used without image auto-correction. Especially the massive (unusable) barrel distortion requires countermeasures. With all corrections in place, the center performance of the lens is just outstanding but there’s a sharp drop in resolution towards the outer image field at f/2.8. The quality of the outer image field improves when stopping down and is decent albeit unimpressive at medium aperture settings. Lateral CAs are low. There is some vignetting at f/2.8 even with auto-correction …well-controlled when stopped down. The quality of the bokeh is good for an ultra-wide lens.…we aren’t all that thrilled by the build quality. The rather mediocre plastics and sluggish AF don’t scream quality. …this has to be seen relative to the low price tag. Keeping this in mind, it’s almost surprising that the lens features some degree of sealing against moisture as well as an impressive close focus capability with an object magnification ratio of up to 1:2.
Overall, the Tamron 20mm f/2.8 Di III OSD M1:2 is a good lens for a great price but it’s not an obvious choice.
Tamron 24mm F/2.8 Di III OSD M1:2
The Tamron 24mm f/2.8 Di III OSD M1:2 stays a bit short of the optical quality that we have seen from the Tamron 35mm f/2.8 Di III OSD M1:2 but it’s still a very sharp lens. The center quality is absolutely superb. The outer image field shows no weakness even at f/2.8 but it stays short of exciting results even when stopped down. However, there’s a caveat. Image auto-correction does reduce the corner quality due to a rather excessive amount of barrel distortion. …While you will see somewhat softer corners, the lens has still enough potential for maintaining a good quality in the outer image field though. CAs are quite low and usually not an issue even in RAW images. The vignetting is heavy at large apertures unless you activate image auto-correction. …you can achieve a decent amount of object separation at close focus distances. The rendering of out-of-focus highlights is decent for a moderate ultra-wide prime lens.The build quality has to be seen in the context of the price tag. Obviously, it is a consumer-grade lens so don’t expect wonders in this respect. The use of plastics is perfectly fine but they have a rather mediocre feel to them. The rather sluggish AF doesn’t help with the subjective quality perception. On the positive side, the lens features some degree of sealing against moisture. Macro photographers will also appreciate the close focus capabilities with an object magnification of up to 1:2.
While the Tamron 24mm f/2.8 Di III OSD M1:2 is a decent lens, it still feels like an answer to a question that nobody has asked. Most standard zoom lenses cover the 24mm setting and the speed and quality advantage of the Tamron lens is either marginal or non-existent. But … it’s cheap.
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Tamron 20mm F/2.8 Di III OSD M1:2（Model F050):
B&H Photo / Amazon / Adorama
Tamron 24mm F/2.8 Di III OSD M1:2（Model F051):
B&H Photo / Amazon / Adorama
Tamron 35mm F/2.8 Di III OSD M1:2（Model F053):
B&H Photo / Amazon / Adorama