Voigtlander Super Wide-Heliar 15mm f/4.5 Aspherical III

[Eriksen]

Is this distortion normal for that lens? I use it on a Sony A7III camera.

[Lightshow]

All ultrawides have some distortion, it increases as you go further from the center.
https://www.flickr.com/photos/lightshow-photography/tags/voigtländer1545superwideheliarversion3/

[philslizzy]

I would consider it distortion free. some ultrawides have significant barrel distortion. I have an earlier version of this lens and apart from the vignetting I'm very happy with it.

[dan_]

That's not distortion. It's just how the correct perspective looks at such an wide angle of view. With this FL you should take much care that all the verticals should remain verticals (especially those far from the center of the image) when making the photo (=the sensor plan should remain strictly vertical). Any small inclination of the sensor plane much accentuates the inclination of the out of center verticals at this wide angle of view. But that's the effect of the large angle of view, not a perspective distortion. A perspective distortion would result in bent or not strait out of center verticals and horizontals. That's not the case in your image.
The lens (I have it myself) really has no visible distortion.

[Lightshow]

It is distortion, it's called Perspective Distortion.
https://en.m.wikipedia.org/wiki/Perspective_distortion_(photography)
https://fstoppers.com/architecture/how-lens-compression-and-perspective-distortion-work-251737
https://photo.stackexchange.com/questions/48689/photo-stretched-at-corners
https://www.picturecorrect.com/tips/how-to-work-with-wide-angle-lens-distortion/
UWA short focal length lenses tend to stretch the image as you get farther from center, it's more obvious with faces than landscapes.
But as far as the more common Pincushion or Barrel Distortion, the CV15III has almost none.

[dan_]

You are right. In photography, when a camera position produces a perspective that makes an object or scene look different than we might expect it to look that is called "perspective distortion". In this regard all the wide and tele lenses are producing "perspective distortion". But the term "distortion" in this case is somehow improper used because the perspective itself is correct (correctly re-sampling a geometrical linear perspective), just different of how we expect it to be.

On the other hand the lens distortions (Barrel, Pincushion and Mustache Distortions) are real distortions of the linear geometrical perspective that are induced by lenses.

By "perspective distortion" I wanted to say a distortion of the linear geometrical perspective but you are correct, the term "perspective distortion" has its own, different meaning photography. Thanks for the correction.