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p.1 #6 · p.1 #6 · A9 dynamic range: choice or side effect of sensor? | |
Jonathan Brady wrote:
I'm pondering the DR of the Sony α9 and why it's lower at base ISO than the other Sony cameras, and even less than the (lower MP) Canon 1DX Mark II. I'm wondering if it was a conscious choice on Sony's part, or if it is a side effect (limitation) of the new sensor design.
The reason I'm wondering about this is the feasibility of a Sony α9R (or perhaps a Sony α7RIII). If this was a conscious choice on Sony's behalf - a trade-off like Canon and Nikon have done (1DX Mark II and D5) to favor better performance at higher ISO, then it's irrelevant for an α9R or α7RIII. But, if it's a side effect, or limitation, of the stacked sensor design, then unless Sony pulls out some wizardry, those cameras will likely have less DR than the α7RII.
Does this matter? Probably not, for me anyway. There's only about 2/3 of a stop of DR difference between the α7RII and the α9 at base ISO and I'm not the kind of user to exploit that difference.
This is just stuff rolling around in my head. Any thoughts?...Show more →
With BSI you profit more with smaller pixels. But if I look at Bill Claffs read noise values, the A9 seems to be tuned for higher isos. The gain changes at around iso 640 reversing the performance compared to the A7rii. Another change of slope seems to be at around iso 1600, where now both A7rii and A9 read noise curves have the same slope, with the A9 being lower in magnitude. Interestingly you find the A9 to be slightly better from this iso on when looking at the DR measurements of DXO, too.
A recent report on Sony (Dpreview):
And as we learned during our visit, most of the advancements in the a9 stem from new sensor technologies.
Two to three years ago, how would it have been possible to predict sensor readout speeds that offer autofocus calculations at 60 fps and a fully electronic shutter that is only a stop behind the speed of mechanical shutters?
[...]Yasufumi Machitani, project leader on the a9, talked to us about the development of the camera. A number of its features, like blackout-free shooting and fast AF/AE calculation, require sensor readout speeds conventionally thought impossible. A stacked BSI-CMOS sensor with integral memory was necessary for these technologies, and the camera division’s awareness of such coming sensor technology years in advance allowed it to plan the a9.
I guess that, together with the differently tuned sensor, the new sensor technology is another factor as suggested by others, too.
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