Nikon's New Z6 III Has a Super Fast Sensor You Probably Don't Need

Nikon's Z3 III brings a mysterious new sensor technology to its already impressive Z6 line. 

Nikon is on a roll with amazingly capable cameras, and the Z6 III keeps up the streak. Its new "partially stacked CMOS sensor" lets it shoot better video and focus faster and in lower light. Other than that, this is yet another solid win from Nikon, although perhaps the additions are geared more towards videographers than still photographers.

"As late to the party as Nikon was with professional mirrorless cameras, it’s leaps ahead like this that remind us of Nikon’s history incredible engineering chops. I’m not in the market for anything like this but it’s great to see Nikon still at it!" writes photo enthusiast Velvet Spaceman in a Verge comments thread.

Stacked

When you take a photo, the sensor records the amount of light hitting each of its millions of pixels. That data then needs to be read out from the sensor into the camera's computer memory, where it can be processed into RAW files and JPGs and then stored on the card.

Different types of sensors read that data out in different ways. The slowest is to read one line at a time, moving each pixel down that line until it reaches the end, then moving on to the next line and starting over. Ideally, then, you want to get the data-reading circuitry as close as possible to the photo sites (aka pixels) to make the readouts faster.

The problem with this is that the circuitry then gets in the way of the sensor and impairs its light-gathering ability. To fix this, CMOS sensor makers invented "backside-illuminated" sensors. Essentially, they shave the back off the CMOS sensor so the light can get in that way. Flip the sensor around, and you've just put all that circuitry behind the sensor, out of the way of the light.

Stacked CMOS sensors go one better. Imagine making several sensor circuit boards, shaving off the backing, and very carefully stacking them on top of each other so everything lines up. This lets you do things like mounting the RAM directly behind the pixels and getting near-instant readouts.

This speed is what lets stacked CMOS perform incredible feats. The readouts are fast enough that the camera doesn't even have to blank the live feed from the sensor to the viewfinder, which means you can shoot full-resolution pictures at up to 20 frames per second while still watching the subject in real-time.

As you can imagine, though, stacking those layers is still an expensive business, which is where Nikon's brand-new partially stacked CMOS comes in.

ImPartial

Nikon has not released details of the new sensors. Not from a technical point of view, at least. But DP Review's Richard Butler offers a partial explanation. It looks like Nikon has kept much of the readout and analog-to-digital conversion circuitry at the edges of the sensor chips but has stacked them there, enabling faster readouts. The result is a speed roughly only a quarter of that of a fully-stacked CMOS, but it's still faster than regular non-stacked chips. And as we shall see now, it's more than fast enough.

The $2,500 Z6 III offers 6K video at up to 60fps in N-Raw mode and can spit out 50 full-resolution JPGs in a single second. That's nice, but unless you're a videographer or sports photographer, it's also somewhat academic. More immediately useful are the improvements the sensor makes to focus, which can now work down to -10ev. This means that it can focus under starlight without having to engage the camera's "starlight mode."

Focusing is also, says Nikon, 20% faster than on the previous model, the Z6 II.

Truly, we are in an age of incredible cameras. They can capture sharp images in any light, and they can do it faster than anyone needs. At this point, the technology is so good that, unless you are working at the cutting edge of a specialist field, any camera is going to be more than good enough. In this light, Nikon's choice to go with a less-capable partially-stacked CMOS sensor seems a smart one, keeping the price (relatively) low in this non-flagship model while neatly improving several key functions by quite a margin.

"The real dis/advantages are around usability and ergonomics. These cameras have a vast plethora of capabilities and are very complex. For people who earn $ from media creation, ease of use matters more than other specs. And its a challenge the manufacturers haven't overcome as yet," photographer JKGal wrote in a forum thread participated in by Lifewire.

But when it comes to buying a camera, the basic performance of pretty much every model is so good that you want to think instead about ergonomics, lens and accessory selections, and whether what you actually want is a small, compact camera that's always with you or a bigger all-purpose beast like the Z6 III. Faster isn't always better.