Dynamic range
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Dynamic range

The Sony a7R II boasts a significantly higher base ISO dynamic range than the a7 II, and this relationship is maintained until the two camera's highest ISO settings. Both are superior to Canon's EOS 5D III. Source: Bill Claff

The a7 II's older 24MP sensor lags behind the newer a7R II in terms of dynamic range at all ISO sensitivity settings. At the all-important base ISO (ISO 100 in both cameras) the difference is a little under one stop. The gap closes a touch from ISO 200-400 but widens again thereafter, thanks to the a7R II's dual gain technology kicking in at ISO 640. At these higher ISOs, the signal is effectively amplified even further, but early on - at the sensor read-out stage - to help protect if from noise.

Very few things ignite (or should that be ignorate...?) quite as much argument on DPReview forums and comment sections as dynamic range, but the basic fact is this: greater dynamic range, especially at base ISO, means greater latitude for exposure adjustment in Raw mode. In cameras that offer very good dynamic range, like the a7R II and Nikon D810 (just to take two examples) this effectively negates the requirement for graduated neutral density filters, and greatly expands a photographer's ability to capture a full tonal range in a single exposure.

The a7R II is better than the a7 II in this regard, but both are better than certain full-frame DSLRs in this class (we've plotted the EOS 5D III in this graph, from Bill Claff) that are limited by relatively high levels of noise in shadow areas. This can become problematic when Raw files are manipulated too heavily, and limits your ability to expose images for the highlights.