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Z8 extremely unreliable/inconsistent AF in mildly low light

  
 
coralnut
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p.20 #1 · p.20 #1 · Z8 extremely unreliable/inconsistent AF in mildly low light


It's a good thing when the problems that you've been discussing are recognized by the social media 'influencers' that have Nikon's ear.


May 19, 2024 at 10:43 AM
ronno
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p.20 #2 · p.20 #2 · Z8 extremely unreliable/inconsistent AF in mildly low light


I can't read through this whole meandering thread right now…
but can someone tell me if these focus issues occur with F/2 .8 and faster lenses?
(when I was having these focus issues it was with a f/4.0 zoom lens...)

Thanks!



Jun 07, 2024 at 12:45 PM
bernardl
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p.20 #3 · p.20 #3 · Z8 extremely unreliable/inconsistent AF in mildly low light




snapsy wrote:
Received new mannequin today with glass-type eye and eyelashes.

Here is an informal eye AF vs eyelash test on both the Z8 and R3, using each system's respective 50mm f1/.8 lens. This test was under ~7EV conditions. Both cameras had significant trouble locking on the eye of this new darker-skinned mannequin. As for focusing on the eye rather than eyelash, most of the Z8 shots had the eyelash in focus whereas the R3 had the eye in focus.

Here's an animated PNG showing 100% crops:

Z8 Eyelash test, Animation of 100% Crops (14 MB)
R3 Eyelash test, Animation of 100% Crops (10 MB)




How come the ISO of the Z8 is 1250 while the Canon is 250?

Cheers,
Bernard



Jun 08, 2024 at 06:50 AM
snapsy
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p.20 #4 · p.20 #4 · Z8 extremely unreliable/inconsistent AF in mildly low light


bernardl wrote:
How come the ISO of the Z8 is 1250 while the Canon is 250?

Cheers,
Bernard


Different matrix/evaluative metering algorithms between the cameras.



Jun 08, 2024 at 07:16 AM
ilkka_nissila
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p.20 #5 · p.20 #5 · Z8 extremely unreliable/inconsistent AF in mildly low light


ronno wrote:
I can't read through this whole meandering thread right now…
but can someone tell me if these focus issues occur with F/2 .8 and faster lenses?
(when I was having these focus issues it was with a f/4.0 zoom lens...)

Thanks!


Focusing in low light is more reliable with faster lenses, but I don't have a lot of experience on situations where one would use the lens stopped down to a smaller aperture (in low light) and use flash to bring in light; in those circumstances some problems may occur, but I haven't run into them in practice (maybe because this is not a typical scenario for me, but also because the lenses I use are very sharp and contrasty and this helps with the AF). I mostly shoot f/2.8 and f/1.8 Z S-line lenses. When I tried the 24-70/4 and F-mount 70-200/4, it became immediately clear that its AF wouldn't work acceptably in low light situations for my uses. With the lenses that I own, I don't really run into these issues, but most of the time I do shoot wide open when photographing moving subjects that might require eye autofocusing, and when I do shoot stopped down in low light, it is with studio flashes that have their modeling lights (which are continuous lights) and so the problem goes away because the modeling light gives the subject enough light. When I shoot in low available light indoors without using studio flashes, I am almost always wide open, so the AF system gets more light than with an f/4 lens. If I were to e.g. shoot at f/5.6 and mostly bring in the gap in lighting using speedlights, I might very well run into an issue but I don't like the aesthetics of those apertures and the "all-flash" lighting, instead preferring to let in enough ambient light and use a wide aperture.



Jun 09, 2024 at 04:33 AM
bernardl
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p.20 #6 · p.20 #6 · Z8 extremely unreliable/inconsistent AF in mildly low light




snapsy wrote:
Different matrix/evaluative metering algorithms between the cameras.


Same light level?

Cheers,
Bernard



Jun 09, 2024 at 07:43 AM
snapsy
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p.20 #7 · p.20 #7 · Z8 extremely unreliable/inconsistent AF in mildly low light


bernardl wrote:
Same light level?

Cheers,
Bernard


Should be. Both were indoors with my shutters set the same, and shot in quick succession between the two.



Jun 09, 2024 at 09:04 AM
 


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LostLensCap
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p.20 #8 · p.20 #8 · Z8 extremely unreliable/inconsistent AF in mildly low light


SCoombs wrote:
This is an issue I've been fighting with and trying to get a better handle on for a while: in even just slightly lower light, I have found the Z8's subject detection to become extremely unreliable, especially in AF-C.

To be clear, by "slightly lower light" I'm not talking about anything extreme, but something like "there's bright sunlight streaming in through my bay windows and I have someone standing 15 feet away where the sun isn't reaching so I need ISO 2000 at f4 and 1/200" sort of low light.

Also to be clear, by "extremely unreliable" I don't mean that
...Show more
Why I keep my D850




Jun 10, 2024 at 07:59 PM
Kipple
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p.20 #9 · p.20 #9 · Z8 extremely unreliable/inconsistent AF in mildly low light


Is it possible VR is contributing to this lack of reliability with focus in lowlight

Edited on Jun 11, 2024 at 04:01 AM · View previous versions



Jun 11, 2024 at 03:52 AM
Kipple
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p.20 #10 · p.20 #10 · Z8 extremely unreliable/inconsistent AF in mildly low light


SCoombs wrote:
As noted, it does work well with single point mode. Not "precise on every shot," but more like "close enough you can't usually notice it on three out of four shots."

This doesn't mean there's no reason to want to have the "eye-AF" working in situations where the flash is required, or that we can't find it weird that in the very same situation an AF point placed on the eye by the user will work very reliably while the same point place there by the subject detect system will usually not get good focus.


When you say it works well with single point mode do you mean it works with single point AFS or AF-c.

Is it also a problem with single point AF-c

I was about to buy a Z9 in the next couple of days but this is putting me off now.

I can live with using single point in AF-c but it MUST work in lowlight conditions.

I quite often shoot at 1/200 sec F2.8 ISO 3200-6400 using a D850 with 105mm F1.4E at distances of between 6ft-10ft and this seems to closely match the type of scenarios where you encounter the reliability issues with focus being off

If a Z9/Z8 cannot focus reliably at those levels of light with AF-c in single point then it would be useless to me.




Jun 11, 2024 at 03:58 AM
Kipple
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p.20 #11 · p.20 #11 · Z8 extremely unreliable/inconsistent AF in mildly low light


snapsy wrote:
Today I decided to look deeper into the eye AF issues for the 4EV lighting conditions. It occurred to me that perhaps the issue wasn't specific to eye AF or AF-C but simply that the camera's PDAF wasn't sensitive enough for these lighting conditions. To test this theory out I switched to a fixed camera position and added a focus reference to detect if/when the AF was hunting. It's hunting constantly. Then I switched to a higher 6.5EV and confirmed the hunting almost completely disappeared. Then I switched back to 4EV and started experimenting with AF-S and other focus area
...Show more

Did you have VR/IBIS on when you did the tests



Jun 11, 2024 at 06:28 AM
bs kite
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p.20 #12 · p.20 #12 · Z8 extremely unreliable/inconsistent AF in mildly low light


Kipple wrote:
When you say it works well with single point mode do you mean it works with single point AFS or AF-c.

Is it also a problem with single point AF-c

I was about to buy a Z9 in the next couple of days but this is putting me off now.

I can live with using single point in AF-c but it MUST work in lowlight conditions.

I quite often shoot at 1/200 sec F2.8 ISO 3200-6400 using a D850 with 105mm F1.4E at distances of between 6ft-10ft and this seems to closely match the type of scenarios where you encounter the reliability issues
...Show more

My Z8's AF is no less effective in low light than my D850 is. They both work well in low light.





Jun 11, 2024 at 06:41 AM
ilkka_nissila
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p.20 #13 · p.20 #13 · Z8 extremely unreliable/inconsistent AF in mildly low light


bs kite wrote:
My Z8's AF is no less effective in low light than my D850 is. They both work well in low light.



I agree on my part, when there is too little light to work with on a Z8, there is probably too little light to work with on a D850 as well, and in bright or intermediate light the Z8 is much more accurate.

However, as I've said before I mostly work with fast lenses in low light and don't typically stop them down in such circumstances. Stopping down (e.g. to f/5.6) puts the Z mirrorless cameras at a disadvantage as they fully take advantage of the benefits of larger apertures in terms of benefiting the AF in low light, whereas with a DSLR anything larger than f/2.5 or so can become less accurate overall, f/2.8 is close to the sweet spot for DSLR AF. For the Z cameras, if you shoot at a stopped down aperture, you're also focusing at that aperture (unless it is smaller than f/5.6), which means there is less light to focus based on for those stopped-down photos than wide open. If you shoot an f/2.8 or faster lens wide open, you should get very good AF in low light with the Z8, Zf, or Z9.



Jun 11, 2024 at 07:19 AM
Buckeye2604
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p.20 #14 · p.20 #14 · Z8 extremely unreliable/inconsistent AF in mildly low light




Kipple wrote:
Is it possible VR is contributing to this lack of reliability with focus in lowlight

I think Scoomb determined that the issue he was experiencing was related to flash settings - TTL.



Jun 11, 2024 at 10:00 AM
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