Curious: why don't sensors & lenses have same shape?
Feb 6, 2018 07:52:31 #
Feb 6, 2018 07:58:00 #
The only benefit I can see to a round sensor would be eliminating the need to rotate into portrait mode for a vertical shot. Which ever mode, a significant area of the sensor would be rendered useless. Also, we are used to viewing artwork rectangular. It's much better compositionally than a circle.
Feb 6, 2018 08:04:18 #
Feb 6, 2018 08:26:23 #
To add to the musings... I have always wondered why things are reversed left-to-right in a mirror, but never top-to-bottom. And, BTW, rotating the mirror doesn't change anything!!!
Feb 6, 2018 08:33:08 #
I think it is the way that light enters the lens and then crosses over in the barrel - round keeps everything equal. Rectangular would change the travel time of the rays of light. The cross over of a ray coming from the corner would lag behind that from the center of the rectangle.
Feb 6, 2018 08:38:37 #
sueyeisert
Loc: New Jersey
LoneRangeFinder wrote:
Here’s another puzzler: “Why do we drive on a parkway and park on a driveway?”
I like it.
Feb 6, 2018 08:46:02 #
Feb 6, 2018 08:48:37 #
tuatara
Loc: Orig. NZ - currently SF area
Dragonophile wrote:
If sensors are rectangular or square, why aren't lenses? One of those questions that pop into your head as you are trying to fall asleep at night.
Manufacturing! The process of making the chips is easier when they are cut off of the base wafer in a linear fashion rather than round, plus there is a lot of waste between the circular components, and very little between rectangular components.
Lenses are round because light focuses to a point. Get a square magnifiying glass and see if you can focus to a square point, and maufacturing is easier with round, a square lens has a lot of waste in the corners.
Feb 6, 2018 08:53:23 #
ToBoldlyGo
Loc: London U.K.
Leitz wrote:
Are you aware that you're making Chris T jealous?
Oh come on, comments like this are just childish. Grow up.
Feb 6, 2018 09:16:09 #
I have an old rectangular magnifying glass made for reading. I doubt that it was very expensive.
I just checked and visually there is no discernible distortion when held parallel to the object being viewed. But, if it is tilted the distortion is terrible.
I just checked and visually there is no discernible distortion when held parallel to the object being viewed. But, if it is tilted the distortion is terrible.
Feb 6, 2018 09:17:05 #
ToBoldlyGo wrote:
Oh come on, comments like this are just childish. Grow up.
having read the thread, your point is...
Feb 6, 2018 09:20:30 #
Dragonophile wrote:
If sensors are rectangular or square, why aren't lenses? One of those questions that pop into your head as you are trying to fall asleep at night.
The laws of physics / optics. Actually some medium format lenses have had rectangular baffles or masks inside, but the lens barrel and glass are round. What are you taking to fall asleep? Hash Oil?
Feb 6, 2018 09:23:41 #
Leitz wrote:
Are you aware that you're making Chris T jealous?
I think this one is even beyond Chris.
Feb 6, 2018 09:27:04 #
Dragonophile wrote:
If sensors are rectangular or square, why aren't lenses? One of those questions that pop into your head as you are trying to fall asleep at night.
Why not Polygonal to match the Iris Leaves, or Round Leaves to match Round Lens Glass? Is the Ugly Hedgehog becoming Facebook with idiocy!
Feb 6, 2018 10:49:18 #
Refractive lenses, like MOST of our camera lenses can only be ground in a circular pattern. Sure, you could turn a rectangular blank or cut off the edges of a round lens but that would come with a simple problem. ALL of the lens provides light to all of the image. If you cut off any part of the lens to make it rectangular, the image would be darkened, it would not change shape i.e. become rectangular. Does the image on the sensor become smaller the smaller the lens opening? NO, Of course not. It just becomes darker. Why would one reduce the effective maximum f/stop?
In reality, there can be a rectangular lens shape. It is a fresnel lens. This type is usually associated with lighthouses and focusses the beam from the lamp. Canon has a few DO or Difractive Optic lenses that use the fresnel principle but they too are circular for the same above reason. The engineering needed to make a rectangular difractive lens that gave consistent even light over the image sensor would be cost prohibitive and would not approach the light gathering ability of a circular lens.
In reality, there can be a rectangular lens shape. It is a fresnel lens. This type is usually associated with lighthouses and focusses the beam from the lamp. Canon has a few DO or Difractive Optic lenses that use the fresnel principle but they too are circular for the same above reason. The engineering needed to make a rectangular difractive lens that gave consistent even light over the image sensor would be cost prohibitive and would not approach the light gathering ability of a circular lens.
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