a7RIV vs a7RIII DR

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JimKasson
JimKasson Forum Pro • Posts: 26,275
a7RIV vs a7RIII DR
19

At the a7RIV announcement, Sony used language that made many think that the camera made impressive strides in dynamic range over its predecessor, the a7RIII. There were discussions in this forum. Now that I have the a7RIV in my hands, I can disabuse you of any such thoughts.

Let’s dissect the above graph. The horizontal axis is the mean signal level in stops from full scale. The rightmost part of the graph is 4 stops down from full scale, so we’re already at middle or dark gray there, and it gets darker as you go to the left. The vertical axis is the signal to noise ratio (SNR) normalized to a 1600-pixel-high print. The black line at 3.3 marks the Claff PDR threshold (log base 2 of 10 is 3.3). The Claff PDR is measured by looking at where each curve crosses the black horizontal line. On the right side of the graph, the most important determinant of the SNR is the full well capacity (FWC) of the camera. On the left, the read noise comes into play. Higher is better.

The a7RIV trails its predecessor by a small amount in the brighter portion of the image, and by a slightly larger amount in the stygian gloom. The GFX 100 does better than both by virtue of its greater sensor area.

Details, other ISO settings, here:

https://blog.kasson.com/a7riv/sony-a7riv-vs-a7riii-shadow-noise/

Jim

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