Nikon is claiming image quality that is a full stop better at every ISO, e.g. ISO 12800 is as good as ISO 6400 on the D810. Apparently without losing quality at the base ISO.
And that’s what I want to know: how does ISO 64 perform? Because for most of my work on a tripod, I am always shooting ISO 64 on the D810. Nikon doesn’t get too specific, but it sure sounds like ISO 64 ought to be improved. As per Nikon:
Nikon's first back-side illuminated (BSI) full-frame sensor with no optical low-pass filter — at the heart of the D850 is a Nikon designed sensor like none before it—a back-side illuminated (BSI) FX-format full-frame CMOS image sensor with 45.7 megapixels and no optical low-pass filter. A marvel of ingenuity, it achieves extraordinary image quality, enhanced light gathering efficiency, faster data readout and truer color. And with such a dense array of pixels, there's virtually no risk of moiré.
Faster, richer, sharper processing — faster than EXPEED 4, EXPEED 5 quickly processes all 45.7 megapixels of data for lower noise, wider dynamic range, subtle tonal and textural details, high-speed continuous shooting at approx. 9 fps1 and full-frame 4K UHD movie recording.
Sensitive to every little detail — the lower the ISO, the greater the dynamic range. Like the D810 before it, the D850 has the lowest base ISO of any DSLR or mirrorless camera2—ISO 64 (expandable down to ISO 32).
The D850 allows landscape photographers to capture a diverse range of scenes in sumptuously rich detail. It is the first Nikon D-SLR to use a backside illumination sensor, which allows incoming light to reach photodiodes more efficiently. Together with the camera’s low-noise performance, this enables it to achieve ISO 25600 despite its high pixel count. What’s more, it strikes an optimal balance between sensor sensitivity and the volume of light information accumulated in photodiodes, yielding images with a wide dynamic range even at ISO 64 (expandable to ISO 32 equivalent) — the lowest native ISO setting offered by any camera manufacturer. Copper wiring is used to cut electrical resistance, while the backside illumination structure allows a flexible wiring layout, reducing stray capacity. These measures enable 45-megapixel FX-format images to be captured at continuous shooting speeds of 9 fps*1. And because the sensor is designed without an optical low-pass filter, it can harness the sharpness of 45 megapixels when combined with the high resolving power of NIKKOR lenses. The D850 yields pictures that can be enlarged as massive
I’m a little nervous about what “optimal balance” means; the translation in plain English in my book is a compromise of some kind. I care little about high ISO; I just want the best possible low ISO quality. But maybe that language is just badly chosen.
ISO 32 is not a real ISO and with the D810 it damages sharpness and changes the tonal mapping, so I do not consider it useful on the D810. But I’ll look into it on the D850.
Comparing ISO 64 on the D810 versus Nikon D850 probably means 3 and 5 stop push tests since well exposed images look terrific on the D810. Already the Nikon D810 mostly eliminates the need for any HDR work (compared to other DSLRs); if the Nikon D850 takes it further along then Canon shooters are in a world of image quality hurt by comparison (if that is the priority), since Nikon is already way ahead with the D810.
With all this work on image quality, it’s crazy not to implement the low-hanging fruit of optimal exposure capability.