If the camera lens was round, why make rectangular film? Early camera makers decided upon rectangular film for a couple of reasons.One of the reasons makes common sense, if you think about it. Think about all of the pictures you see, whether they’re photographs, paintings, or posters. What shape are they? The vast majority of them are rectangular or square. Why is that?
If you think about displaying pictures, we usually display them on walls, which are what shape? You got it: rectangular or square. When it comes to framing and displaying pictures, it’s much easier to use a rectangular or square shape, because the frames are easier to create and they’re easier to display on walls of a similar shape.
So it’s only natural that camera makers would’ve thought about making film that would create rectangular photographs. Practically, though, there was another reason. If you’ve ever seen film from an older camera, you know that it comes in a long strip that unwinds as pictures are taken. It’s simply more efficient to use rectangular film in a camera rather than a series of ovals or some other shape.
Likewise, today’s modern image sensors in digital cameras have retained a rectangular shape. In addition to maintaining the traditional shape of film, using a rectangular sensor also leads to better pictures.A round camera lens does produce a round image inside the camera.
However, the outer edges of the round image will have more distortions, sometimes called aberrations, than the parts of the image closer to the center. This is because light must be bent more to reach the outer edges of the circular image.
To correct for these aberrations and end up with the best image possible,the rectangular sensor crops out the outer edges of the circular image from the lens. In other words, it only keeps the best part of the image from the lens. This gives you better photographs than you would get if you kept the entire circular image from the lens.