There have been reports that the new Nikon Z6 III may have a more limited dynamic range than the old Z6 II. The observation was made by William Claff of Photons to Photos, who does in-depth tests on camera sensor performance and more. Claff’s findings show that the Z6 III can achieve a maximum of 10.44 EV of dynamic range at ISO 100, compared to the Z6 II’s 11.26 EV at the same sensitivity. The Z6 III lags behind its predecessor by 0.6-0.7 EV all the way up to ISO 800, where the two cameras perform very similarly:
Read more: Nikon Z6 III review
Claff clearly knows what he’s talking about and has been testing sensor performance for years, so I’m not going to criticize his results or testing methodology. What I can say, however, is that when I tested the Z6 III in the lab, I found that (contrary to Claff’s results) the Z6 III’s dynamic range was nearly identical to the Nikon Z6 II at lower sensitivities, though the new camera lagged behind the previous generation by 0.5-1 EV at ISO 6400 and above.
While this is surprising and disappointing, the most noticeable difference between the two cameras for me is their signal-to-noise ratio – or how much image noise each camera produces at a given ISO sensitivity. In our signal-to-noise ratio test, I found that the Z6 III and Z6 II generated very similar noise levels at lower sensitivities, but by ISO 1600 the new camera starts to produce noticeably more noise than the Z6 II, and this trend continues all the way up to ISO 25,600 – our highest sensitivity tested.
And we’re not the only ones who’ve noticed the Z6 III produces more noise at higher ISOs. Check out this detailed comparison of the noise in this camera’s footage against the original Z6 from YouTuber testcams:
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While you’d be forgiven for assuming that a new camera would outperform the camera it replaces in every test, this is often not the case. In general, a new camera model that has a higher megapixel count than its predecessor will often produce a lower signal-to-noise ratio, because cramming extra pixels onto the same-sized sensor – whether that’s APS-C or full-frame – makes each pixel smaller, less light-sensitive, and therefore more prone to generating noise.
However, in the case of the Z6 III, the 24.5MP resolution is identical to that of the Z6 II. The difference here could instead be due to the Z6 III’s new partially stacked sensor construction. Again, this is speculation rather than fact, but while a partially stacked sensor improves sensor readout speed for faster burst shooting and reduced rolling shutter distortion, it can also come at a cost to image noise and dynamic range. This is also supported by the sensor results on Photons to Photos, which generally show that dynamic range performance from stacked sensors is slightly lower than that of equivalent, non-stacked chips.
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I can’t give you a conclusive explanation for why a stacked sensor would compromise image clarity and dynamic range, but I doubt it’s due to the stacked sensor construction itself. Simply stacking elements of a sensor on top of each other doesn’t necessarily hinder image quality. It’s more likely that this design is used to increase the readout speed of a sensor, though logically even this doesn’t really add up. To capture a single still image, the sensor in the Z6 III uses the same (or nearly the same) number of pixels as the sensor in the Z6 II. Both sensors have identical dimensions, resulting in identical pixel sizes. If the image is then captured using the same shutter speed and ISO sensitivity, the two cameras should produce very similar noise levels and dynamic range, assuming the Nikon’s image processing is also comparable. And yet our lab test results are consistent with those of other testers: the Z6 III doesn’t perform as well as the Z6 II (or even the original Nikon Z6) in terms of dynamic range and image clarity. The increased reading speed of the sensor is the most obvious cause.
But before you take your new Z6 III back, let’s zoom out a bit. The differences in image quality between the two Z6 models that emerged from our and William Claff’s lab tests are relatively minor. In our case, we tested with all high ISO noise reduction turned off and all dynamic range enhancements disabled, to maintain a level playing field. In more ‘real world’ use with these systems enabled, would you really notice such subtle differences in image quality unless you were deliberately looking for them? Unlikely.
And when you consider what a faster readout speed can mean in terms of higher burst shooting speeds, higher video resolutions at faster bit/frame rates, and other image quality improvements like less rolling shutter distortion, many would argue that this increased versatility of the hybrid camera is worth the small compromise in noise and dynamic range.