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> "Kenneth" <kdw### [at] gmail com> wrote:
>
>>
>> But a problem arose when doing the animated matchmoving: POV-Ray's default
>> perspective camera is a 'perfect pin-hole' camera. A 'real' camera is not; its
>> lens has spherical aberration...
>
> Oops, what I meant to say was 'barrel distortion' (and 'pincushion distortion'
> and etc.) Spherical aberration is different, a lack of perfect focus of
> different wavelengths of light. My Canon camera shows very little of that.
>
Barrel distortion, also called barelling, is when straight lines curve
outwars. Most common lenses are not corrected, only premium,
professional grade ones are. It's a common distortion for whide angles
objectives.
The oposite distortion, called cushioning, is sometimes visible with
telephoto images, often the cheapest ones.
The aberation due to different wave lenght is calles chromatic
aberation. Normaly, the various objectives have good correction of this one.
Spherical aberation cause a coma effect. Bright points at some distance
from the axis tend to show some egg or plume shaped fuzzyness oriented
radialy arount the center point of the image. It's also present at the
center, but much less noticeable as it's often mistaken as glare. It's
due to the fact that rays hitting the lense at the center converge
farther than those hitting it near the edges. It's compensated by having
stronger curvature at the center than at the edges, making the shape
elliptic.
Barreling can be simulated using the spherical or ultra whide angle POV
cameras.
Alain
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