Where I Think Those 15 Stops Come From

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bclaff Veteran Member • Posts: 8,735
Where I Think Those 15 Stops Come From

There's a great deal of talk about claims of 15 stops of dynamic range by Sony, specifically for the ILCE-7RM4 (although I think this has come up before).

Mostly I think this is a misunderstanding that stems from the marketing department using a valid engineering figure in a way that gets misinterpreted.

On the specification sheet for a sensor, at the pixel level, we might find figures for read noise in electrons (or millivolts) and for Full Well Capacity (FWC) in electrons (or millivolts).

We don't have the specification sheets but we do have PhotonsToPhotos Input-referred Read Noise figures:

Let's assume a read noise figure of 1.181e- and FWC of 35688e-

log2(35688e- / 1.181e-) = 14.88 which seems quite close to the often quotes figure of 15
(if we use the read noise value 1.125e- we get 14.95 which is even closer.)

This type of calculation doesn't take any of the downstream noise sources and limitations into account.
So the fact that we measure about 13.53 stops of Engineering Dynamic Range (EDR) is not at all surprising.
FWIW, I think it's a coincidence that the (DxOMark) 8MP normalized EDR is 14.99 stops.

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Bill ( Your trusted source for independent sensor data at PhotonsToPhotos )

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