Why are camera lenses always round in shape?

how could you screw it in if it wasn't round

Hmm..look at your eyes..! good question though,

VERY difficult to cast optical glass in any shape other than round, and the most important part of a lens is the very middle because the optical adjustments of each lens rely on how the image is refracted through the center of each lens (most camera lenses have at least three individual lenses inside them).

if there not round it is difficult or imposable to get an Even curvature over the whole thing, you don't want the corners to have distort due to a different curve

A lens bends light beams to a certain total degree, no matter the light beam's angle of entry. This total "bending angle" is determined by the structure of the lens.

A lens with a rounder shape (a center that extends out farther) will have a more acute bending angle. Basically, curving the lens out increases the distance between different points on the lens. This increases the amount of time that one part of the light wave is moving faster than another part, so the light makes a sharper turn.

Increasing the bending angle has an obvious effect. Light beams from a particular point will converge at a point closer to the lens. In a lens with a flatter shape, light beams will not turn as sharply. Consequently, the light beams will converge farther away from the lens. To put it another way, the focused real image forms farther away from the lens when the lens has a flatter surface.

Increasing the distance between the lens and the real image actually increases the total size of the real image. If you think about it, this makes perfect sense. Think of a projector: As you move the projector farther away from the screen, the image becomes larger. To put it simply, the light beams keep spreading apart as they travel toward the screen.

The same basic thing happens in a camera. As the distance between the lens and the real image increases, the light beams spread out more, forming a larger real image. But the size of the film stays constant. When you attach a very flat lens, it projects a large real image but the film is only exposed to the middle part of it. Basically, the lens zeroes in on the middle of the frame, magnifying a small section of the scene in front of you. A rounder lens produces a smaller real image, so the film surface sees a much wider area of the scene (at reduced magnification).

First of all, lenses are obtained from spheres. They are cut out from spheres. That is why they are curved. All lenses are curved in shape. It is not possible that a lens is straight.

Study an eye,whatever you see it all passes through one point and reversed image is inside .
if in case of camera lens if it shaped in other shape concentrated rays which are to be passed through a point has to be of the shape of lens .this process of reversing of image takes place many a times in camera and finally in the eyes.
then think what shape it shoud have.
JUB DUNIYA GOL HAI TO ____

Lens making is an art and it probably grew as an art over decades if not centuries. What we see today is a perfect lens reached after numerous innovations and corrections to achieve optical quality and colour corrections etc. I hope the following will shed some more light onto the subject of lenses:

http://en.wikipedia.org/wiki/Carl_Zeiss
http://en.wikipedia.org/wiki/Single-lens...
http://electronics.howstuffworks.com/cam...

cameras always have round lenses in order to get maximum coverage.As one may realize,for a given perimeter(length),circle has the maximum surface area.So in order to facilitate greater coverage and faster capturing techniques, round lenses are used.moreover round lenses are much more easy and cheap to manufacture as compared other shapes