Originally posted by beholder3 That sadly is marketing b/s.The Sony dual gain sensors deliver no more detail, they lag behind actually at given lighting situations.The a7r3 is actually the worst performer with regards to ISO invariance of those three cameras. The ten year old K-5 (within its apsc limits) outshines an a7r3 on ISO invariance until ISO 1600, same as a Nikon D7000.Looking at the actual images easily reveals this.
Sorry, I didn't express that clearly. I was discussing PDR measurements and why I think that dual gain makes sense for the A7RIII or IV sensors. And, again, for a sensor with higher noise than the excellent K-1 (and K-5) at base ISO, why strict ISO invariance
is not desirable. If you start from a good high-ISO performance and extrapolate that to low ISO in the sense that "the low noise level is maintained even at base ISO", it surely is. But for sensors with mediocre low-ISO dynamic range, such as older Canon sensors, you do want to reduce the (absolute) noise level as you increase ISO, so that your dynamic range can become competitive at high ISO - one reason why Canon cameras were competitive e.g. for sports photographers.
What I meant to say is that in the PDR over
nominal ISO, the A7RIII
measures better only due to the switchable gain. Otherwise either low-ISO or high-ISO would suffer. I don't have access to any A7Rxx, and can only observe published shots. Comparing the low-light DPR shots visually at higher ISO, I would say that K-1 and A7RIII are head-to-head there at the same
nominal ISO in terms of shadow detail: Some areas look better for one, other areas for the other. Combining that with the observation that ISO is overstated by 1/2 EV (according to DXO), it confirms a stated advantage of the K-1 over the A7RIII. Applying the shift in the PDR curve would make them (only) identical: Again, a testament to my statements above how the measured PDR isn't sufficient to describe the visual quality with respect to noise in detail. PDR is a necessary, but not sufficient criterion for good visual appearance. Some very gentle noise reduction may indeed be at play here.