Originally posted by 6BQ5 Wide angle lenses tend to have a fisheye effect. This can be noticed by zooming out and then getting real close to someone for a portrait. Their nose will be huge! Most photographers want a flat field across the lens.
The volume anamorphosis (that's a mouthful) of facial features has nothing to do with fisheye lenses* or with flat field optics. What it does have to do with is the rules of perspective which are driven by the position of the lens relative to the subject. Even flat field lenses with excellent rectilinear projection exhibit this feature. What is closer appears larger because it is closer. The only reason the subject appears distorted is that the wide angle lens provides a wider field of view than a "normal" lens at the same distance and allows us to see elements of the subject that are at greater relative distance. You can test this by doing a crop of a "distorted" big nose/chin wide angle portrait and comparing it to a photo taken with a longer lens from the same camera position.
It cannot be stated strongly enough that this is the case for any lens that provides a wide field of view for a particular frame size (format) and is not a property of focal length
per se. 28mm is a wide angle focal length on my 35mm film and will provide a very satisfactory duck face when mounted with my KX film camera. The same 28mm lens on my smaller APS-C K-3 provides a fairly flat and boring "normal" perspective.
Steve
* As with all wide angle optics, fisheye lenses will record anamorphosis, but it is unrelated to the lens' optical design which counter-intuitively actually provides less true volumetric distortion of objects at edge of field than a rectilinear lens of the same FOV.
---------- Post added 05-31-14 at 11:32 PM ----------
Originally posted by jatrax I know. I just meant that if the OP is APS-C only then just ignore the crop thingy
Sorry I was not more clear
It was my intent to affirm and agree with what you had said. My bad.
Steve