What mainly limits dynamic range in a digital camera sensor?
Asked 1/5/2014
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I’m trying to understand what sets the dynamic range of modern digital cameras. I first assumed the analogue-to-digital converter bit depth would be the main limit because it determines how many discrete levels can be recorded. Is that actually the key factor, or are there more important limits in the sensor and readout system?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
12y ago
2 Answers
9
No. This is like saying you can determine the height of a house by counting steps to get up. The size of steps matters and so does the number.
Dynamic-range should be determined by the well-depth (size of capacitors at a photosite) and noise floor (how much noise in the system when these is no signal). Knowing these two, one can compute the dynamic-range of a camera with good accuracy. Improving either will also improve the dynamic-range a camera can capture.
Originally by user1620. Source · Licensed CC BY-SA 4.0
user1620
12y ago
0
Generated from our catalog & community — verify before relying on it.
ADC bit depth is not usually the main factor by itself. Dynamic range is primarily set by the ratio between the sensor’s maximum signal and its minimum usable signal.
In practice, the two key limits are:
- full-well capacity: how many electrons a photosite can hold before it saturates
- noise floor: the amount of noise present when little or no light is recorded
So dynamic range depends on how far apart those two limits are. A larger full well increases highlight headroom; a lower noise floor improves shadow detail. Knowing those two values gives a good estimate of a camera’s dynamic range.
ADC precision still matters, but it is more like how finely the available range is divided up. If the sensor and electronics are noisier or saturate earlier, more ADC levels alone will not create more real dynamic range.
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