Why do smartphones keep landscapes sharp even with wide apertures?
Asked 3/8/2018
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Smartphone cameras often have wide maximum apertures like f/2.2 or f/2.8, yet they can still keep most or all of a landscape in focus. I thought landscapes usually need a smaller aperture such as f/5.6 or f/8 for greater depth of field. How do phones achieve this with a fixed wide aperture?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
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It's worth noting that sensor size plays a huge role in depth of field and behavior of the lens.
A smartphone has a tiny camera sensor, often around 25 square mm. This gives the camera a crop factor of about 6. (For the Samsung S9, I'm not sure about the dimensions.)
You can calculate the hyperfocal distance (or "depth of field") but you can also get a pretty good estimate by multiplying the f/ number by the crop factor to know what your effective f stop is. On a sensor of roughly 25 square mm, your F/2.2 behaves a lot like a f/13.2 aperture lens would on full frame.
Originally by user20357. Source · Licensed CC BY-SA 4.0
user20357
8y ago
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Because depth of field depends on more than just the f-number. Sensor size and focal length matter a lot.
Phones use very small sensors, which means they use very short actual focal lengths to get a wide view. Short focal lengths naturally produce much deeper depth of field than longer lenses. So even at f/2.2, a phone camera can behave more like a much smaller aperture would on a larger camera format.
For distant scenes, depth of field is huge anyway. If the camera is focused near infinity, objects tens or hundreds of meters away can all appear sharp. With the very short lenses used in phones, the “everything from roughly here to infinity” zone starts quite close.
So the reason a smartphone can shoot a sharp landscape at a seemingly wide aperture is mainly:
- tiny sensor
- very short focal length
- subjects often being far away
That’s also why phones struggle to create strong natural background blur compared with larger-sensor cameras.
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