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 p.1 #17 · Z8 extremely unreliable/inconsistent AF in mildly low light | |
ilkka_nissila wrote:
Could you show what the light looks like without the flash (including ISO, aperture and shutter speed information)? (The flash won't help the AF.)
I don't think it's a question of the subject detection mistaking pizza for an eye, but the pizza has high-contrast texture which produces a meaningful contrast that the camera can focus on, while the eye surrounded by soft skin might not, in low light, produce adequate contrast-to-noise ratio for the system to work with.
I haven't really had difficulties with my Z8 in low light except when talking about extremely low light (such as 1/50s, f/1.4, ISO 25600 and backlight at that). I agree that having some direct light on the subject helps a lot. But mostly I use the D6 and Zf in low-light people and event photography and not the Z8 simply because the 20 and 24 MP sensors produce to my view better image quality in these conditions and the smaller files are faster to work with as well. I wildlife photography I have used the Z8 in fairly low light (1/200s, f/5.6, ISO 25600) and there can be difficulties for sure, but again the image quality wouldn't be that great even if the shots were in focus, and so I find the major limitation here the maximum aperture of the lens and the image quality that the sensor can produce at these ISO settings. I think the biggest focus limitation is related to the lack of cross-type sensors in the Nikon Z cameras (the D6 obviously has them, and is in some situations much more reliable, such as when the subject is in backlight and the background has brightly lit vertical lines). However, this is not consistently related to low light levels as it can happen in bright sunlight.
Canon has the advantage in low light because all of the sensor photosites are used for phase-detection whereas in the Nikon/Sony designs the phase-detection sensors constitute only a small part of the sensor area. However, the latter design has the advantage that the camera doesn't have to deal with twice as much data (i.e. 90 MP camera sensor when the files are delivered with 45 MP of data). I think some of Canon's overheating problems with the R5 are related to the quantity of data that has to be processed in their system. ...Show more →
If we were talking here about something like the wide area large box with no subject detection and the camera going after the pizza because it's got more contrast that would make perhaps some sense, but we're talking about the system confidently identifying the eye and putting a small AF box on it. There shouldn't be any way for the system to suddenly go after the pizza, which is not in this case blocking the eye and is not anywhere near the box the AF system reports it is using. Moreover, there are the other examples I posted where the focus landed on something else with about the same or with literally the same contrast as the eye it said it was focused on. I have posted some screencaps from NX Studio on DPreview which show the focus points.
It's also worth nothing that I'm far from the only one who has reported this experience, as evidenced by some of the posters in this thread as well as in plenty of other discussions on the topic in the past. On the other hand, I'd agree that some report not having the problem, and I've read enough threads to thus far not have been able to find an obvious difference in what people from either group are doing, how they're setting things up, how they're trying to use the AF, etc.
As far as natural light levels go, I don't have photos readily available to post of this but I have kept track of this and we're talking about anything on the darker end from something like ISO12800 at 1/160 f4 - which I'd admit is getting pretty dark - all the way to something more like ISO 3200 at f4 1/160, which is not all that bad, to something like ISO 1600 at f2.8 and a shutter in the range of 1/400, which is really not what I'd call extremely dark. Another way of putting it is that it happens in light that's low but still good enough that without the flash I can get usable photos.
Another way of putting it, and this is the most important practical issue, if the light is low enough that I need to use a flash *at all*, this whole dynamic comes into play. In other words, anytime I would ever need to use the flash I can't count on the system to focus on eyes more than 1/3 of the time unless I place a focus point manually.
Edited on Apr 26, 2024 at 07:08 AM · View previous versions
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