Why don’t camera makers use circular sensors to capture the lens’s full image circle?
Asked 11/28/2018
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If a lens projects a circular image, why are camera sensors rectangular instead of circular? A circular sensor seems like it could let you choose any aspect ratio or orientation later, without rotating the camera for portrait shots. Since lenses often cost more than the camera body, why not make the sensor large enough to cover the full image circle and crop as needed?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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I've often wondered that myself. Some possible reasons:
- You will either waste a lot of silicon in places that will never get light (near the edges) or you'll have a round wafer that is harder to manufacture.
- The resulting software will either have to waste cycles processing the junk data in those unused parts or will be significantly more complex.
- Sensor readout is challenging if the rows have variable length.
- There may or may not be adequate space for sufficiently large reflex mirrors, requiring either more interesting (multi-flip) SLR designs or mirrorless designs.
- Some lenses have parts that are shaped in ways that prevent getting a full circle.
- Your average user will likely find a round sensor harder to use unless the default behavior is to show a normally cropped rectangular image, which requires additional hardware (e.g. a partial blackout LCD in the OVF).
That said, the idea is not without merit. There's more discussion on the subject here:
https://www.diyphotography.net/circular-image-sensor-best-thing-ever-heck-yeah/
Originally by user25054. Source · Licensed CC BY-SA 4.0
user25054
7y ago
0
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Mainly because it’s impractical and offers limited real benefit. Image sensors are manufactured and read out in row/column structures, so rectangular sensors are much simpler to make and process. A circular sensor would waste silicon near the edges or require harder manufacturing, and reading variable-length rows would complicate electronics and software.
There are also camera-design issues: in SLRs, a larger circular sensor could conflict with mirror size and movement, and some lenses or internal lens parts may not deliver a clean, usable full circle in a way that helps real-world shooting.
For most photographers, a rectangular frame is also easier to compose with. Cameras can already offer multiple aspect ratios by cropping a rectangular sensor, and rotating the camera remains the straightforward way to change orientation while keeping full use of the sensor area.
So while a circular sensor sounds flexible, the added complexity, cost, and wasted area generally outweigh the convenience.
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