why are lens's round? Why not the shape of the sensor?

[alfa147x]

why are lens's round? Why not the shape of the sensor? I'm thinking if the lens were rectangular their would be less glass meaning cheaper lens's right ? I know im wrong but i just want to know why ...

 

[rudder]

because the light would not come in from all around and the pictures would look like crap.

 

[JulesMaximus]

Because light is being focused by the lens and if the lens isn't perfectly round and precisely concave or convex (depending on the lens) it will focus light to different areas of the sensor. There are many lens elements in a camera lens and they are all designed to transpose a large image onto a relatively small canvas. A square lens would not work.

 

[DrPizza]

I'm not positive, but I believe round lenses are far easier to manufacture. Additionally, it seems (at least to me) that a rectangular lens would merely be a round lens that's trimmed into a rectangular shape. It's been 2 decades since I had an optics course; so my knowledge is really rusty. However, if you do a google search for ray diagrams and lenses, it may answer your question.

You'll want to read about focal point. Also, perhaps a good jumping off place would be to look at ray diagrams of a parabolic concave mirror. Light hitting the mirror is reflected through the focal point of the mirror. It's too bad I don't have you in my classroom - I could show you how an image is produced with a concave mirror. You'd see why it's necessary that the mirror is round (except, of course, that you could get out a wet saw and chop it into a rectangular shape.)

 

[alfa147x]

Originally posted by: DrPizza
I'm not positive, but I believe round lenses are far easier to manufacture. Additionally, it seems (at least to me) that a rectangular lens would merely be a round lens that's trimmed into a rectangular shape. It's been 2 decades since I had an optics course; so my knowledge is really rusty. However, if you do a google search for ray diagrams and lenses, it may answer your question.

You'll want to read about focal point. Also, perhaps a good jumping off place would be to look at ray diagrams of a parabolic concave mirror. Light hitting the mirror is reflected through the focal point of the mirror. It's too bad I don't have you in my classroom - I could show you how an image is produced with a concave mirror. You'd see why it's necessary that the mirror is round (except, of course, that you could get out a wet saw and chop it into a rectangular shape.)

My dad just got done telling that over dinner; a much more simplified version: their would be extra cutting involved so it wouldn't actually be cheaper...

 

[mdcrab]

It's hard to screw a square peg in a round hole. Threads are easy easy to cut and pretty much self sealing. Mechcanically it would cost more to have a slide or clipping type mechanism and most likely more to difficult to have a seal that would last.