Getting started with the Nikon Z6 III: the ISO increase of the sensor in detail

Brand new hot, the freshly announced Nikon Z6 III has arrived at the lab Digital. We will certainly have to wait a little (patience!) for a complete test, but we have already warmed up the new 24×36 24.4 Mpx sensor against our famous test pattern.

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A sensor which has its importance in the equation since Nikon presents it as the first sensor “partially multi-layered“. Here, a small technical point is necessary. Nikon’s formula – which always has somewhat confusing in-house translations! – corresponds to what is called in the jargon a stacked sensor.

Industrialized by Sony, first in small smartphone sensors, the stacking of several layers of electronics makes it possible to move the circuits, notably the analog-to-digital converters (A/D converters), not next to the colored sub-pixel , but below.

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There are several advantages to this. The first is to limit electromagnetic pollution around the photodiode by moving the circuitry to another layer. The other is the additional space for the circuitry that this provides: with a classic design, the surface area is very limited. By taking advantage of its own dedicated layer for the components (converters, but also memory), the sensor designer can benefit from increased processing power and a surplus of information storage memory, while pushing higher the playback frequencies.

This sensor design is more expensive because the electronics often have to be designed on another silicon wafer and glued with great precision behind the photosensitive part. To limit the cost increase, Nikon has placed the additional components not below its pixels, but next to the photosensitive part, on the front of the sensor, outside the image circle.

On the one hand, the amount of circuitry to be added is less than with a truly stacked sensor, on the other hand, the positioning requires less precision — in the case of a truly stacked sensor, each pixel is connected to a dedicated converter! If the burst values ​​will be evaluated in the field, the question was therefore whether this design had an effect on the increase in high sensitivities.

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Steps at 1600 and 6400 ISO

We compared its ISO increase with two direct competitors: the Sony Alpha A7 IV and the Canon EOS R6 Mark II. The first has a 30 Mpx sensor, the other 24 Mpx. And their positioning in the range and price at launch is close.

What we notice right away is the intensity of the smoothing at the 1600 ISO level. While the details are perfectly preserved up to 800 ISO, we notice that the image quality deteriorates on the Nikon Z6 III. A loss of precision is also present with the Canon EOS R6 Mark II, but a little less significant. As for the Sony A7 Mark IV, it has the triple luxury of pushing this level to 3200 ISO, with less loss of precision and higher definition.

As the sensitivity increases, the quality of the Nikon gradually degrades, as with the Sony. The exception being Canon which, although generally less precise at lower ISO values, offers the most regular degradation up to ISO 51,200. Beyond that, we find ourselves faced with pixelated watercolors for all the protagonists.

Although this is only a first test shot, we can however suspect one thing in the Nikon Z6 III sensor: its very high reading speed seems to have an impact on its image quality. With a raw burst of up to 20 fps and jpeg bursts of 30 to 120 fps, the Z6 III targets sports and action photographers. However, as we have seen on ultra-fast sensors, in particular the global shutter sensor of the Sony A9 Mark III, the very high reading speed requires electronics (A/D converters, etc.) that consume energy and generate more interference – and therefore digital noise – than slower sensors. Nikon’s dual ISO circuit helps limit damage and provides good image quality up to ISO 6400.

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Note here that this is an evaluation of the quality of jpeg compression by default. It will also be necessary to evaluate what the raw files produce when they are handled by demosaicing software. And determine, at that moment, the acceptable limit values ​​in terms of image quality – modern noise reduction algorithms are now doing an astonishing job.

The cameraness Nikon hits the mark

While we will have to wait for the test to have a final opinion on the body, a first lab run and a few manipulations allow for a first evaluation… quite subjective. If Nikon’s nature and sport DNA means that large bodies like the Z9 and Z8 make perfect sense with the quality long focal lengths that the company markets, the fact remains that they are bulky and heavy.

While it may not have the compactness of some cameras, notably Sony’s A7C II/R, the Z6 III is nevertheless more compact, lighter and more manageable than its big brothers, while maintaining an excellent impression of robustness and reliability. A feeling that Nikon had conceptualized with the portmanteau word cameraness. A cameraness which allows the Z6 III to really stand out from the competition from Sony and Nikon, without having to pay too high a price in terms of weight and size. Here we feel the ergonomic know-how of the brand’s case engineers!

However, we regret that Nikon does not offer many compact lenses. Indeed, its 40mm f/2.0 does not offer stellar image quality. And on the contraryits Nikkor Z 50mm f/1.8 S may be very good, but it is a bit bulky with its 8.7cm barrel.

And the rest of the test? Besides the field trips and other AF measurements, we will have to wait for Mr. and Mrs. Adobe to integrate support for raw files within CameraRAW. At least that will be necessary in order to evaluate the image quality of this singular sensor, partially stacked…

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