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I don't know why I am not at all tempted by a full frame ultrawide.

Now I understand why Tokina had to make their 16-28 big and heavy with a protruding front element.

APS-C offers you much more often needed DOF a more dramatic perspective,way cheaper prices and much lighter alternative.

3+EV vignetting is the least to say unacceptable.

Losing sight of equivalence again.

 

To get an equivalent lens on APS-C, you are talking about 10-22mm f1.75 lens. Wanna bet on how vignetting for the 10mm f1.8 end would be on on APS-C?

 

You do not get more DOF on APS-C either, when you set equivalent settings. So, APS-C does not have a DOF advantage, nor will it vignet lens at equivalent settings.

Nor will it give more dramatic perspectives.

 

Just set your EF 16-35mm f2.8 L USM III to 16 mm and f13 and you get the same of less vignetting as the APS-C lens at 10mm f8, and the same DOF.

You can not set the APS-C lens to 10mm and f1.8 though, and that is where the FF lens has the advantage (when needed).