QuantumTarsus wrote: ruthenium wrote:
Since you mentioned "better ISO performance than a lot of FF sensors" - this is incorrect, if you mean high ISO. Better base ISO, yes, in the sense that the dynamic range is better.
This chart seems to show superior DR at every ISO than the A7RV. That said, I'm not one to obsess over charts. The extra stop of DR isn't enough in and of itself to warrant the GFX over the A7RV, but its there if needed (though it really is a secondary benefit).
My way of looking at this is by assuming that the same total amount of light falls on the A7RV and GFX100 II sensors. Then the two cameras are expected to have their ISO differ by the factor of 0.62. For example, when the GFX is at its maximum native ISO 12800, the A7RV should be at ISO 8000. The corresponding PDR number is indeed slightly better for GFX100 II 6.37 vs 5.88 for A7RV. I expected these to be practically the same.
An important point, it would be unfair to compare the PDR at the same ISO value (if this is what you do), e.g. 12800 for both GFX100 II AND A7RV, because this would mean that we deliberately starved the latter of light (and thus made the S/N worse).
For another, extreme example: we set the
GFX100 II and an MFT camera Panasonic G9II to produce equivalent images. The first is at 35mm, f4 and ISO 12800, the second is at 12mm, f1.6 and ISO 2000. The SS is the same on both cameras. The PDR values are 6.37 vs 6.53, respectively. There is no advantage to shooting the GFX at high ISO in terms of the PDR or noise, because the smaller sensor cameras are capable of producing equivalent images without going to the same high ISO range as the medium format camera must use.
We may recall that the ISO is related to the amount of light that falls on a unit surface area. As the sensors get larger, the same total amount of light divided by the increasing surface area gives less light per unit surface area, hence the ISO should be raised.
Note, interestingly, that in some poor light one can raise the ISO to 12800 on A7RV but in this same light, under equivalent shooting conditions, the GFX100 II would have to lower the SS instead if we stay within the native ISO range.
Jun 24, 2025 at 07:25 PM
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