Could a camera use a 36×36 mm square sensor, and would that count as medium format?
Asked 6/6/2016
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Lenses project a circular image, so could a camera use a square 36×36 mm sensor instead of the usual 36×24 mm full-frame sensor? If it’s technically possible, why is it uncommon, and would a 36×36 mm sensor be considered medium format?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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That's not correct. Look at this picture:
The green rectangle is a 36x24 sensor. The green circle, which has a diameter of 43.3mm, is the minimal light spot needed for that size. The blue square is 36x36 sensor. The blue circle, which has a diameter of 50.9mm, is the minimal light spot needed for that size. As you can see a lens suitable for 36x24 does not necessarily cover the whole 36x36 frame.
As for the second part of your question - it is possible to qualify such sensors (in my opinion) as medium format because the most of available "full-frame" lenses will not cover these bigger sensors and so you'll need other lenses.
Originally by user44894. Source · Licensed CC BY-SA 4.0
user44894
10y ago
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Generated from our catalog & community — verify before relying on it.
A 36×36 mm square sensor is technically possible, but a standard 36×24 mm “full-frame” lens usually will not cover it.
The key limit is the lens’s image circle: it must be at least as large as the sensor’s diagonal. A 36×24 mm sensor needs about a 43.3 mm image circle, while a 36×36 mm sensor needs about 50.9 mm. So a lens designed just to cover full frame may vignette heavily or leave dark corners on a 36×36 mm sensor.
That’s why “lenses are round” does not automatically mean you can fit a larger square sensor behind them.
Square sensors and square image formats are possible — film cameras have used square formats, and some specialized digital cameras/sensors do as well. They’re uncommon mainly because most photography and display uses favor rectangular aspect ratios, and camera/lens systems are designed around those formats.
As for whether 36×36 mm is “medium format”: it’s larger than 35mm full frame, and in practice it would likely need lenses with a larger image circle than standard full-frame lenses. So it could reasonably be grouped with medium-format territory, though naming conventions are partly historical as well as technical.
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