Warren D
Well-known member
I found the observation that the Z9 af is better if the image displayed in the VF is properly exposed interesting: https://www.zsystemuser.com/nikon-z-system-news-and/reader-questions-answered.html
Z9 AF Operation Observations by Thom Hogan
- Thread starter Warren D
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John Navitsky
Well-known member
i antidotally noticed this when shooting black dogs doing dock diving, but i didn’t have enough data points to consider it more than a hypothesis
Yes. I notice it, too.
Same with the Z6/7ii's.
Same with the Z6/7ii's.
agdoherty
Active member
I also wholeheartedy agree with his comments re: nikon’s LUT for Z9 video. it’s not really useable, and manual color grading for video gives much better results. The color is nice, but exposure is way off in every editing program I’ve imported it to.
In reading this article he says to use Lossless compressed format for RAW and goes on to say why he thinks this. My camera was set at this and that is what I have been shooting without any issue in-camera or with Adobe software, color is great, no problems downloading or processing. Am I missing something here? His article has a May 15, 2022 date on it. Any insights here?
The AF comments confuse me a little. Is the z9 actually stopping down the aperture to the user setting when it focuses, or is it like a dslr focusing wide open?
I suppose the claim would be easy to test by shooting a well lit focusing target with progressively lower and lower exposure to see if it fails to focus even in good light based on reduced exposure as he claims. And then do the opposite test, take something in low light that won't focus then increase exposure to see if it then would focus.
I suppose the claim would be easy to test by shooting a well lit focusing target with progressively lower and lower exposure to see if it fails to focus even in good light based on reduced exposure as he claims. And then do the opposite test, take something in low light that won't focus then increase exposure to see if it then would focus.
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DanG
Well-known member
Since the firmware update, I noticed (as Steve suggested) that the AF Large is not quite the same with animal detection. I now find myself using the 3D more often where I can quickly grab my subject. Anyone else leaning this way? The Large AF is not quite as sticky as it was and I am struggling a bit with it.
TonyF
Active member
Thanks for posting
. I'ts a useful article. I've had similar experience with the HE* files (wont be using anyway until DXO start to support them) and the exposure (helpng focus) observations have got me thinking on the scenarios where Ive had a few too many misses.PS / for info - Delkin Black 128GB card with up to 1700mbs write speed handles lossless raw for stills with no problems. I think only Grays of Westminster stock them in the UK.
DsD
Well-known member
I read his recent articles too and find it very interesting that focus is coming from the vision stream.
I wonder if canon, sony and the likes are taking focus off the sensor and why they might be faster and more sticky with certain subjects and in certain circumstances?
John Navitsky
Well-known member
i don't think we can really read too much into this. it simply means the subject detection is being performed post gain adjustment. it may or may not be part of the vision stream
DsD
Well-known member
Thanks John. I am not very technoid when it comes to such stuff. Probably should have kept my mouth shut!
Perhaps this will help, at least for the Z9.
If you look at Nikon’s descriptions the processor is handling dual streams - live view and image data. I don’t think we quite know what data is passed back and forth, under the heading of ‘compensation and image processing’. There is an impact from the live view data though.
I don’t recall hearing about EVF live view data and dual stream processing until the Z9. So I’m not sure if other Z cameras have dual stream processing or not? Although again, there's evidence that EVF settings do affect AF.
Seems to be missing a few details.
John Navitsky
Well-known member
yah, that's a marketing thing, not anything you can really use to significantly improve your understanding on how the system works
FB101
Well-known member
I think you guys are complicating things too much. In the z9, artificial intelligence has evolved and a.i now means actual intelligence. Which means that focusing is actually managed by little gnomes instead of chips (which really helped supply lately).
‘Nikon has an exclusive agreement with desert gnomes, which means they do great in harsh bright lights even with washed out contrast; that‘s what desert gnomes are good at Because they use colors to see things, not contrast.
unfortunately Canon snatched the contract with the deep cave gnomes that are really great at seeing in pitch dark, so Nikon had to settle for British gnomes - they are pretty good in gloomy light but they just don’t see as well in pitch black.
And here you go, sometimes the simplest explanation is just the right explanation. Now I need to find that salamander and recharge my flash.
‘Nikon has an exclusive agreement with desert gnomes, which means they do great in harsh bright lights even with washed out contrast; that‘s what desert gnomes are good at Because they use colors to see things, not contrast.
unfortunately Canon snatched the contract with the deep cave gnomes that are really great at seeing in pitch dark, so Nikon had to settle for British gnomes - they are pretty good in gloomy light but they just don’t see as well in pitch black.
And here you go, sometimes the simplest explanation is just the right explanation. Now I need to find that salamander and recharge my flash.
froolk
Member
I am also skeptical, but how do you know it to be false? It would be easy to empirically test, just keep the light steady but lower the exposure in increments and watch if focus is lost.
John Navitsky
Well-known member
right, but that doesn’t mean it’s using the evf, just imagery after the iso gain is applied
Yeah when I read the linked post it seemed like a bit of a jump to say it's using the EVF stream. Thom is pretty tech savvy and also typically careful of what he publishes. So he likely did some testing to convince himself. But regardless of whether it's the EVF data or not it's good to know that exposure effects AF. Another good argument for practicing ETR when shooting the Z9.
John Navitsky
Well-known member
and that's not to say it's NOT using the evf stream, just that we don't know. one possible reason it *might* be using the evf stream is that it's downscaled. i could certainly see that the image processing done to do subject recognition might not be able to handle full res 45mp at 120fps
FB101
Well-known member
That and the fact that gain has been applied would be 2 good reasons.
Nonetheless, I struggle with the idea. Everybody says that subject recognition in Nikon is color based. So what happens if you apply a B&W profile that shows in the EVF? You lose subject recognition?
John Navitsky
Well-known member
remember, the gain is applied to the stream going to the cards as well.
even if it's from the "evf stream" that can mean a lot of things from a systems and programming perspective and doesn't necessarily mean it's exactly WYSIWYG
Dr_J
Member
Looking at Thom’s companion piece, DSLR versus Mirrorless Overall, his conclusion, ‘So, DSLR users, relax: your cameras still take fine photographs. Mirrorless users, you don't need to keep chasing the fastest model: your current version still takes fine photographs.‘ just seems to make a whole lot of sense, even if we all knew it already 
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Interesting points.
Does focus depend on Picture Control? If camera is set to Vivid (hi contrast), does it focus better than if it's set to Flat (low contrast)?
I've never checked that.
Chris K
Well-known member
Some thoughts:
@bleirer, I believe the camera is stopping down during "live view", to an extent. I've heard others report this is Nikon's method, and I've witnessed it with my cameras. If I remember correctly, it will stop down to f/8 at the smallest? If you want to test for yourself, set your lens to f/8 and point the camera at at light source and a dark spot. You should hear (or see) the aperture blades moving while in live view.
As for the live view exposure affecting AF capabilities, I recall when the Z9 was doing the pre-release rounds, someone (I think Ricci?) said that the Z9 is NOT doing AF off the EVF image like other Nikons do. I give it a 0.1% chance I can find that quote now!
@John Woodworth, your point is an interesting one: if the EVF images affects focus, Picture Control should also affect focus. So, does the camera focus better or worse if you were to set the camera to B&W low contrast versus color high-contrast? Seems like this would be easy to verify using your hypothesis!
@bleirer, I believe the camera is stopping down during "live view", to an extent. I've heard others report this is Nikon's method, and I've witnessed it with my cameras. If I remember correctly, it will stop down to f/8 at the smallest? If you want to test for yourself, set your lens to f/8 and point the camera at at light source and a dark spot. You should hear (or see) the aperture blades moving while in live view.
As for the live view exposure affecting AF capabilities, I recall when the Z9 was doing the pre-release rounds, someone (I think Ricci?) said that the Z9 is NOT doing AF off the EVF image like other Nikons do. I give it a 0.1% chance I can find that quote now!
@John Woodworth, your point is an interesting one: if the EVF images affects focus, Picture Control should also affect focus. So, does the camera focus better or worse if you were to set the camera to B&W low contrast versus color high-contrast? Seems like this would be easy to verify using your hypothesis!