Let's begin by breaking the rule that says you should never start off by talking about what a camera is not.
But it's important that you know the Z 6 is not a step down from the Z 7. It's not a lesser camera; it's a different camera.
Both were introduced at the same time. Both are Nikon professional-level mirrorless cameras. Both are acclaimed for their advanced technology and image quality. Both are really cool.
While they share most features and capabilities, the Z 7 has a megapixel count of 45.7 while the Z 6 is a 24.5-megapixel camera. Which means the Z 6 can do some significant things its sibling can't.
And because all cameras are purpose-driven—your choice will depend on what you do, or want to do, photographically—what makes the Z 6 different may make it ideal for you.
Guided By Purpose
Two senior Nikon managers—Mike Corrado and Lindsay Silverman—got together not long ago with a couple of their associates to talk in general about taking pictures and specifically about taking pictures with the Z 6. Both are passionate, dedicated, driven photographers; if they didn't work for Nikon, they'd be pro photographers. Both had been shooting with the Z 6, and both immediately homed in on the camera's big differences. It was a rapid-fire conversation, which was thankfully recorded.
"You get faster buffering at lower resolution," Lindsay said, "so the Z 6's high-speed framing rate—12 frames per second compared to the Z 7's nine—is going to make a difference shooting motion and action."
"And because of that same resolution difference," Mike said, "there's a difference when you're shooting video. When you go to 4K, you get full pixel readout."
"That means pixel-by-pixel coverage of the scene," Lindsay said. "No line skipping, no algorithms, no interpolation."
"So the result is video that's sharper, smoother—and with less noise," said Mike, who paused briefly before adding, "And because it's a little over half the megapixels [of the Z 7], you get better ISO performance in low light—fewer pixels means larger pixels over the same FX full-frame format surface, so that means a larger light-gathering capability in each of the pixels."
At which point one of their associates mentioned a photographer who was determined to have all things Nikon Z: "I heard from a travel photographer who was planning it out this way: Z 7 for the main camera, Z 6 for the backup, but mostly for video and low-light situations."
"Not an uncommon thought," Lindsay said. "And the Z 6 is also going to be very welcome for photographers who were thinking of getting into video—and now can do so with autofocusing."
"Not to mention wedding photographers who'll take the Z 6 for video and for low-light, photojournalism-style shots," Mike said. "The higher frame rate will pay off for more spontaneous shooting."
Deeper Into Mirrorless
By now you've figured out that working with the Z cameras has offered Mike and Lindsay new possibilities and advantages—which is not necessarily what they expected.
For Lindsay, the surprise was black and white. "I always liked shooting black and white, but now, for the first time, I'm composing in black and white. I set the camera for monochrome, look through the viewfinder and I'm seeing a black-and-white world, and I'm deciding how I want to shoot it. That's cool, and it's amazing."
For Mike the big difference was shooting in manual exposure mode and being able to see the result of his setting’s changes as he made them. "I'm convinced I'm always going to shoot mirrorless in manual," he said. "The technical advantages—seeing what you're going to get in the EVF [electronic viewfinder] before you take the picture, and being able to see the results as you change settings—f/stop, ISO, white balance—has made photography brand new again. And I shoot faster because I can keep my eye at the finder as I make those changes."
Lindsay pretty much summed it up: "The Z 6 comes along at a time when pictures are becoming more important in people's lives, and it's easier now to get good ones," he said. "Most of the features that everyone was excited about in the Z 7—the EVF, the lighter weight and smaller size, the native lenses and their astounding image quality, the compatibility with F-mount NIKKOR lenses that the FTZ adapter offers, the built-in VR—they're all there with the Z 6."
There was a bit more, but you get the idea: for Mike and Lindsay—professionals in practice, enthusiasts at heart—the Z 7 meant getting used to some new possibilities; the Z 6 means fine-tuning the features to their needs.
Welcome to the deeper-into-mirrorless moment.