Ephotozine's "Z6/Z7 Best Overall Camera of the Year 2018"

Started Jan 1, 2019 | Discussions thread
beatboxa Veteran Member • Posts: 7,937
AF-C vs. Tracking

mbecke wrote:

beatboxa wrote:

mbecke wrote:

Lance B wrote:

Ephotozine's camera of the year for 2018 is the Z6/Z7 twins:


A surprising result, no doubt, but there you go.

The D850 got the best DSLR of the year.

500 f5.6 PF got best telephoto lens of the year.

D3500 got best entry level DSLR

D7500 got best Mid Level APS C DSLR

They must not shoot the Z6 in AF-C mode.

Are you confusing subject identification & tracking for AF-C?

These are different things.

I am referring primarily to tracking in AF-C mode. AF-S mode has been perfectly fine. Also, in AF-C mode, there is not an attained focus confirmation like there is in AF-S mode (i.e., focus square goes from red to green). I am guessing that Nikon did not quite have the AF-C focusing system worked out when the camera was manufactured. Hopefully, this will be resolved via a future firmware upgrade. Hopefully.

Correct that there is no attained focus confirmation in AF-C mode. This is likely by design, since the focus never locks--it is continuous (even confirmed by the manual). Just because it confirms, a fraction of a second later, it may no longer be in focus. I agree that I'd like some way to distinguish that the camera thinks it's in focus in AF-C, but this is the challenge: thresholds. Nikon cannot predict when in the future it will lose focus, or how precise focus is, so this confirmation may constantly be flashing. Yes, I'd like to see a firmware update.

But again, tracking is different than AF-C; and from my tests so far, AF-C appears to work fine. Use single point AF-C for a subject moving toward and away from the camera, and the camera keeps up with the focus.

What is not fine is Nikon's subject identification decisions, which is related to tracking. It can also be an issue in AF-S, and I find that it sometimes is.

AF-C & subject identification / tracking are very distinct concepts, and I think many are conflating or confusing the two.

In fact, Nikon's DSLRs even used two completely different sensors for each of these:

  • Autofocus sensor (for autofocus)
  • RGB / exposure sensor for subject identification & tracking

These two sensors communicated with each other but were distinct, sort of like a game of battleship. In other words, imagine you had autofocus points A1, A2, A3, B1, B2, B3. The RGB sensor tells the AF sensor "I think I see an eye. Use AF point B2", then the AF sensor focuses B2. A moment later, the RGB sensor says "The eye has moved. Now use B3," then the AF sensor focuses B3.

In the mirrorless world, these are still, though less, distinct. But with much more information to process, such that:

A Nikon D850 has:

  • ~480 x 360 (0.18 Megapixel) RGB ("tracking") sensor
  • 153 AF points
  • ~20 thousand AF pixels (mix of horizontal / vertical sensitive)

A Nikon Z7 has:

  • 8256 x 5504 (46 Megapixel) "RGB (tracking) sensor"
  • 493 AF points
  • ~3.8 Million AF pixels (all horizontal stripes / vertical sensitive)

And this is even ignoring refresh frequency, rolling shutter, etc.

So the Z7 & Z6 have to process hundreds or thousands of times more information, and limited phase directional information.
And this is probably the root cause of the issue.

The Z's have much more precise information that may not work well with the existing algorithms, causing constant indecision--particularly for subject identification. In addition, we may even see this in the AF-S decisions it makes--I notice that my Z6 is much more prone to focus on the background than foreground images often, even in AF-S. And obviously, the Z's get confused when the only contrast is horizontal.

So the firmware improvement I'd like to see is primarily to subject identification (and therefore tracking).

Effectively, here is the relationship between the two.

  • Admiral Boom (telescope) is like the rgb / subject identification / tracking system;
  • Mr. Binnacle is the AF (including AF-C) system.

And Nikon's issue seems to be with Admiral Boom. Mr Binnacle is doing his job ok.

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