Why lenses are round

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. Check out the following activities with a friend or family member to make some new memories together! Hi, Jeff R.!! We're glad to hear that you like this Wonder, too!

Hi, Pete! Thanks for your comment! The lens is a rectangle and certain technology can change the picture into a circle without using a circle lens. Isn't that cool? Hi, cheyenne! Sometimes the Wonder just sparks our interest to keep learning about the topic! The science behind camera lenses can be a little confusing! We hope you'll explore the topic more by researching online and in books to help you have a better understanding of how lenses work!

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Perhaps one day you can purchase a new one after saving up some money! We're sorry you didn't like today's Wonder of the Day, Amarea! We hope you won't stay gone for long. Thanks for keeping us updated on your name change, Cameron! We think most types of cameras have round lenses - perhaps today you can test this out at home by asking a family member to help you find a camera phone, digital camera and a camera that takes film to look at.

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Want to add a little wonder to your website? Help spread the wonder of families learning together. There are a number of scientific reasons behind the circular shape of camera lenses.

It has been widely observed that in optics, circular or spherical shapes work well, in comparison to others. However, the biggest reason is that rotationally symmetric shapes simply do the job better than any other shape in the camera context. Also, the reasons for such a shape of the lenses vary from manufacturing to lens rotation to a wider perspective. We has tried to search for an answer to this question, now read on to find out the explanations.

So, no need to bother your shutterbugs as your curiosity has been answered here. Generally, it is easier to make circular camera lenses. They are cheaper to make and easier to calibrate when different lenses are combined to achieve a particular power and measure.

Also to produce macro and telephoto lenses, circular is the preferred shape. The opening of a diaphragm and the aperture give rise to a circular space, this is the reason a circular lens will produce the best results. Lenses are round because that is the easiest shape to grind and polish.

Image circles are also round if they weren't they wouldn't be called circles. Photographs are rectangular because that is the way most people want an image to look so the top, bottom and sides are cropped by the rectangluar shape of the sensor.

There was a thread not too long ago arguing for circular sensors so that the image could later be cropped any way the photographer wanted and obviated rotating the camera 90 degrees for portrait orientation, but clearly it was not a popular proposition.

The lens could be made rectangular, but that would needlessly sacrifice either image brightness, or image quality. From any point on the subject, rays of light are captured by the entire surface of the lens, and are focussed to produce the corresponding point on the image. That is, all of the round lens is used to create any given point on the image. If the lens was cropped to a rectangular shape, the image would lose brightness.

Now it is normal to use a variable aperture to control the image brightness, and doing so tends to improve the image quality. The use of a rectangular lens would give a darker image, but the quality would not be improved to the same extent. More importantly, it is usually desirable to make the lens capture as much light as possible. A circle is the optimum shape to achieve this. Attempting to capture the same amount of light with a rectangular lens would result in considerable aberrations and loss of image quality, or might even be physically impossible, since the corners of the rectangle would be part of a much larger circle.

Furthermore, the perimeter of the circular image is less sharp than the center. That is why you want to check the corners of the frame first to see if you have a problem with sharpness. There are arguments in favour of an oversize sensor, such as used in some Panasonic cameras. That enables a chosen rectangular format to be selected with a diagonal which fits within the image circle of the lens. However, such a sensor need not be square.

If you think the doughnut bokeh from the mirror lenses is bad, just picture rectangles all in the background of your images. The lens is round because it's simpler to manufacture and because a lens needs to behave the same way when rotated. If it's did not the distortions would depend on your shooting orientation - very undesirable. The aperture would ideally be round also, but in practice is a multi-sided polygon with either straight or rounded edges that don't quite make a circle.

A perfectly round aperture is desirable for the quality of the out of focus blur. Film was rectangular because it's convenient to make and because paper has always been delivered as a rectangular shape - mainly because it's both efficient to make that shape and efficient to use it.

Round paper and round film would be nightmarish to work with and very inefficient to make. Sensors are round because they must mimic existing film shapes to work with existing technologies in a predictable manner. However the same manufacturing efficiencies apply to sensors as to film, and, if anything, more significant with sensors. In principle there is no reason why you could not make round sensors and use them, however the cost of such sensors would be double the cost of existing sensors, but offer very few advantages in practical terms.

It's also worth remembering that processing image data from a rectangular sensor is a relatively simple task but with a round sensor you add complexity. Surely it makes a lot more sense to design a rectangular lens than a circular one. Surely it is cheaper to make rectangular shaped glass because it is a lot less surface area than circular glass.

The RF should have stood for rectangular frame instead of the nothing it stands for right now. That at least would have given people a plausible reason to consider Canon over the market leader Sony.

All the glass is used in fact. By removing a part of the glass and making it rectangular you would simply remove some light. The waste is that we do not have bigger sensors. With a sensor this is a big waste when you want to crop to I personnally think it would be worth having bigger sensors to take more advantage of the image circle. With Sony you have to remove some parts of the lens to widen the image circle.

The shape of the lens doesn't correspond to the shape of the sensor. Light from all over the circular lens is focussed down to a point on the sensor. If your theory was correct, stopping the lens down would cause massive vignetting on the sensor, it doesn't. The OP's question represents a common misunderstanding on how lenses work. I like these images to explain visually:.

Why are sensors rectangular when lenses are circular? Additionally, corners causes stresses that warp the material. I'd guess the real answer is that film frames are rectangular. But that is a reason why silicon suppliers like it that way.

Right angles appear everywhere in nature and most especially in human construction, while circles appear only rarely, and even then, circles can be easily composed within a square. Not much can be well-composed within a circle.

In all my years of visiting art museums, I've only seen two circular paintings, and a handful of oval ones. Digital images are simplicity themselves, being merely a rectangular array of pixels. A circular image would have to have a more complex structure, and how would cropping work? Would you have to always get a circular crop from your circular image? Before Columbus, the world was flat, and so lenses were flat as well, which is why medieval cameras don't work anymore. Because wild light outside the lens is circular.

Once it enters the lens it is tamed and becomes square. Square light will fit on a square or rectangular sensor. The better question is why are sensors rectangular, not square or even circular, when lenses are invariably circular. That question has been beaten into insensibility in numerous threads here.