Curious: why don't sensors & lenses have same shape? (Page 3): Actually ALL sensors are crop sensors since they crop a rectangular or square portion of a larger circular image. A...

chrisg-optical Loc: New York, NY

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.

Actually ALL sensors are crop sensors since they crop a rectangular or square portion of a larger circular image. A circular sensor can be made to match the circular image from the lens, but that might be a bad thing...the worst performance of a lens is toward the edges, furthest from the optical center. So, in a way cropping that circular image is for the best.

As for a lens shape to match the sensor shape that would be a disadvantage...however a circle (or sphere in 3d) is the most natural shape in existence...everything in the cosmos to nature is circular or spherical in shape (can you think of why the earth, planets, sun, etc., all formed as spherical objects instead of say, cubes or pyramids?) To make a rectangular lens, although possible and even exists in the OVF, would offer no advantage for a main lens that I can think of...not to mention practical issues and manufacturing complexity - circular objects are easier to mold, grind, turn,etc. . Everything turns in a circle...how would you zoom/focus a rectangular lens?

OllieFCR

Creating a lens with reasonable sharpness across the entire area would be extremely difficult with a rectangular lens (maybe not possible) as a rectangle is not as symmetric as a circle, which is the most symmetric two dimensional shape. Pixels need to be a geometric shape that fills all the area of the sensor for best signal to noise; you would have empty space with circular pixels. You could have hexagonal or triangular pixels but what would be the point, harder to make and nothing to gain. You could make the sensors round and there would be only limited wasted area at the edges. But, again, what would be the point? Most people would not want circular pictures printed or displayed.

Bison Bud

I agree with those that have already stated that making a square lens would be difficult, in fact it's probably impossible due to the nature of things. Getting all the light gathered to focus on a single spot would probably be impossible if the lenses were not round. If a square lens could be made to work, it would probably cost a heck of a lot more, due to the engineering involved and at what improvement? If the sensor were made to be round, which could actually work, we'd all be complaining about the distortion around the entire edge, rather than just in the corners. As it stands with a square sensor, it uses only a portion of the image projected by the lens and this effectively crops most of the edge distortion before it ever gets recorded, with the corners being the obvious exceptions. This whole thing brings to mind the old saying: "If it's not broken, then don't fix it!" However, still a somewhat interesting topic of consideration and discussion.

Manglesphoto Loc: 70 miles south of St.Louis

Leitz wrote:

Are you aware that you're making Chris T jealous?

lol!!!!!

Daisy Dog

Instead of rectangular they could make them triangular and eliminate one bump . . .

blackest Loc: Ireland

Actually we are missing the rather obvious, lens elements rotate as they are focused and usually some are fixed and some are moving. Some lens designs have a rotating front element which is a pain when using a cpl filter and one reason for round lens hoods. The petal type can be quite useless on this type of lens.

PeterBergh

chrisg-optical wrote:

... everything in the cosmos to nature is circular or spherical in shape ...

This is only approximately true for the sun and the planets. The sun and every planet in our solar system has a slight bulge at the equator, due to rotation. In addition, the Earth is slightly pear shaped.

It is completely wrong to say that everything in nature is circular or spherical. (Few people are obese enough to be even approximately spherical ;-))

jerryc41 Loc: Catskill Mts of NY

Bill_de wrote:

It's harder to make round picture frames.

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bowserb

All the obvious answers are here. The truth is so obvious, it was hardly worth discussing. However, I still wonder why still camera lens hoods are not rectangular. Look and any cine camera, and you'll see a hood that fits the shape of the film/sensor format. A rectangular hood could be longer and therefore more effective at preventing lens flare. Only drawback I can see is storage.

As to why not a round sensor, that would cost too much for all those pixels that were never used but still had to be manufactured AND had to be processed by the internal CPU after every picture. OTOH, why not a square sensor? With that, you could take a picture in landscape, portrait, or square mode without having to turn the camera. A selector for which format you are using could allow only the required portion of the sensor processed by the CPU. Or the selector could just determine the shape of in camera JPEGs, with RAW being the full sensor every time.

Just thought I'd throw out my own musings... Have a good day, all!

jerryc41 Loc: Catskill Mts of NY

PeterBergh wrote:

This is only approximately true for the sun and the planets. The sun and every planet in our solar system has a slight bulge at the equator, due to rotation. In addition, the Earth is slightly pear shaped.

It is completely wrong to say that everything in nature is circular or spherical. (Few people are obese enough to be even approximately spherical ;-))

True. Nothing in nature is perfect. What amazes me are the many examples of hexagons in nature.

https://www.sciencedaily.com/releases/2008/12/081216104325.htm

Some natural, but mostly man-made examples here.
https://www.google.com/search?q=hexagonal+cracks+in+natural+stone&rlz=1C1CHBF_enUS726US726&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwi3xOmUpJHZAhUSvFkKHR-0Ca0QsAQIKA&biw=1920&bih=900

dcampbell52 Loc: Clearwater Fl

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.

Same reason that 35mm film (and most others) are rectangular. Plus, if film was round and designed to take the image from border to boarder, you MIGHT (depending on lens quality) find that the edges of the image were suffering in quality from the rest of the image.

Fotomacher Loc: Toronto

Bill_de wrote:

Ooops

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Some say pi r square, but I say pie are round, cake r square.

Tomfl101 Loc: Mount Airy, MD

I couldn't begin to explain the square lens question but I have always wondered why very few lens shades are made rectangular. A round design wastes valuable shading that results in flare when shooting toward the sun or other small/hard light sources. An old Leica camera I had the pleasure to photograph with had one. Doesn't seem like a difficult engineering problem to me.

mas24 Loc: Southern CA

Darkroom317 wrote:

Prints weren't always rectangular or square.

https://mashable.com/2016/01/09/early-candid-photography/#h3ESj8mATaqM

Interesting round images, going past a century. 1890s era.

chrisg-optical Loc: New York, NY

PeterBergh wrote:

This is only approximately true for the sun and the planets. The sun and every planet in our solar system has a slight bulge at the equator, due to rotation. In addition, the Earth is slightly pear shaped.

It is completely wrong to say that everything in nature is circular or spherical. (Few people are obese enough to be even approximately spherical ;-))

Still, it has a spherical shape because that is the form of least potential energy (barring outside forces which alter the shape). EVERYTHING in nature is based on the circle, even if the macro object is not. Recall Fourier transforms. Never forget what my 2nd semester EE professor wrote on the chalk board day 1..."It's a sinusoidal world!" And what is the sine wave based on? ... the circle....