Volume Anamorphosis correction

One of the challenges of photographing the real world is that a three-dimensional scene is reproduced in a two-dimensional image. As a result, three-dimensional objects that are not on the optical axis of the camera can appear stretched out. The steeper the angle at which rays from the subject reach the lens, the greater the apparent error — hence these phenomena are particularly noticeable with wide-angle lenses. This stretching becomes even more objectionable the nearer the objects are to the edges of the frame. Volume anamorphosis(sometimes referred to as wide-angle stretching or shape stretching) is occasionally desired as part of a photographic effect, but mostly it has been tolerated as something that was just inevitable.

The volume anamorphosis correction has to be user-set, as it is completely picture-content dependent. Once it is selected, DxO Optics Pro performs the correction automatically.

DxO Optics Pro v5 provides controls for the two most typical cases where volume anamorphosis has the strongest visible impact and takes into account the relevant factors (lens type, focal length, and position in the field) to adjust your image.

1. Choose cylindrical correction to preserve picture components whose curvature is mainly in one direction (such as standing figures, bottles, buildings, trees or architectural columns)

Original image

Cylindrical volume anamorphosis correction by DxO Optics Pro

Photo: Nicolas Touchard

Cylindrical shapes no longer appear fat; monuments are straightened and retain their original proportions; and bodies keep their normal weight!

2. Choose spherical correction for elements with a similar degree of curvature in all directions (such as the human head, tennis balls, apples and oranges)

Original image

Spherical volume anamorphosis correction by DxO Optics Pro

Photo: Jean Luc Dubin

Spheres no longer appear oval; peoples’ faces no longer appear squashed.

3. These corrections are indispensable for wide-angle portrait, social, wedding, and architecture photography

Original image

Cylindrical volume anamorphosis correction by DxO Optics Pro

Photo: Jean Luc Dubin

Whereas cylindrical correction was applied in the above case, in the semi-circular arrangement of the group of figures below, there are fewer important straight lines, in the semi-circular arrangement of the group of figures below, to betray the geometric distortion. However, the figures’ heads (which are fundamentally spherical) appear stretched near the edges of the image. Using spherical volume anamorphosis correction this time produces a more natural result.

Original image

Spherical volume anamorphosis correction by DxO Optics Pro
Photo: Jean Luc Dubin

Lens design is always going to remain a trade-off between correcting for optical distortion and correcting for volume anamorphosis, which are different but related image geometry phenomena.⁽¹⁾

4. Find your ideal balance between volume proportion and geometric accuracy easily

The initial photo of the bridge was taken with a fisheye, which, despite the strong distortion, has well preserved the proportions of the figure on the right and of the lamp-posts well. In the center image, geometric distortion has been corrected, but the figure on the right of the frame and the lamp-posts appear unnaturally ‘fat’ due to volume anamorphosis. In the third image, cylindrical volume anamorphosis correction has restored the lamp-posts and figure’s natural proportions.

Original fisheye lens image

DxO Optics Pro distortion correction

Spherical volume anamorphosis correction & distortion correction by DxO Optics Pro

Photo: Cyrille de La Chesnais

⁽¹⁾This fact - that the laws of physics just don’t allow us to have our cake and eat it too - is reflected in lens design. Fisheye type lenses have huge distortion but very limited volume anamorphosis. Rectilinear lenses display much more limited (though very visible) distortion and very visible volume anamorphosis.

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