Dynamic range and RAW file "bit depth"

Started 11 months ago | Questions thread
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szhorvat
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Dynamic range and RAW file "bit depth"
11 months ago

Most cameras can record the sensor data with at most 14 bits of resolution.  This means that the ratio of the lowest and highest representable values is 2^14.

The dynamic range of a sensor is the ratio between the brightest and dimmest recordable light intensity (or clipping and noise floor).  I notice that DxOMark lists several sensors as having a dynamic range larger than 14 EV, e.g. the Nikon D800 has 14.4 EV, which corresponds to a ratio of 2^14.4.

How can they measure a dynamic range higher than the resolution of the sensor readout?  If the sensor response is strictly linear, this shouldn't be possible.

So is the answer that the sensor response is not linear?  Is this nonlinearity inherent to how the sensor works, or is it a designed feature aimed at increasing the dynamic range?

I'm asking this for my own edification, not because I need the information to accomplish anything.

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