p.18 #1 · Z8 extremely unreliable/inconsistent AF in mildly low light
suteetat wrote:
Yawn, it was good enough to track all kinds of critters in almost completely darkness underwater with f8 and small focus light. They were not stationary and moved a heck of a lot more than a child sitting for a picture.
I think I am about done here. As far as I am concerned, I have no problem with low light AF ability of Z8
These photos have nothing to do with eye AF, and they also are extremely easy situations for the camera since there is only a single object at a single depth for the camera to consider. It's not like a person in a lit room where there are things to focus on everywhere. In these photos the subject is literally the only thing the camera possibly COULD focus on.
p.18 #2 · Z8 extremely unreliable/inconsistent AF in mildly low light
I wouldn't have said it myself, but coralnut makes a good point: if someone is claiming their Z8 doesn't behave this way at a light level of EV4 or lower, it would be extremely easy and helpful and thoughtful to get a spouse or child or friend or some other live person to take a few quick photos at EV4 or EV3 or so. If you get perfect in focus shots, I think we'd all have a lot more confidence in what is going on and it would make it a lot easier for me to convince Nikon to service the camera since I could put my performance up against tests of other bodies. It would only take 5 minutes and I'd appreciate it. Two or three users doing this would make a huge difference.
p.18 #3 · Z8 extremely unreliable/inconsistent AF in mildly low light
SCoombs wrote:
Let me confirm with you: you say this photo was taken at f4, 1/4 of a second, and ISO 25600?
That's *insanely* dark. I can't fathom how the photo has come our with the combination of brightness and noise levels shown here. This is 6 stops darker than the photos I have shown in my previous videos when, without the flash, any photo was almost unintelligible for the level of noise.
p.18 #4 · Z8 extremely unreliable/inconsistent AF in mildly low light
SCoombs wrote:
These photos have nothing to do with eye AF, and they also are extremely easy situations for the camera since there is only a single object at a single depth for the camera to consider. It's not like a person in a lit room where there are things to focus on everywhere. In these photos the subject is literally the only thing the camera possibly COULD focus on.
That would be incorrect. Lots of plankton and critters are attracted by light. Granted nothing quite as big as blanket octopus most of the time but lots of critters got in front, behind etc. The raw image looked more like a mini snow storm. I stamped out a lot of stuffs. Some critters were well less than an inch etc. I know and said from the beginning that I did not use subject recognition since the very first time I mentioned using it in scuba diving at night. But low light, this is way way more low light, I think.
p.18 #5 · Z8 extremely unreliable/inconsistent AF in mildly low light
suteetat wrote:
That would be incorrect. Lots of plankton and critters are attracted by light. Granted nothing quite as big as blanket octopus most of the time but lots of critters got in front, behind etc. The raw image looked more like a mini snow storm. I stamped out a lot of stuffs. Some critters were well less than an inch etc. I know and said from the beginning that I did not use subject recognition since the very first time I mentioned using it in scuba diving at night. But low light, this is way way more low light, I think.
p.18 #6 · Z8 extremely unreliable/inconsistent AF in mildly low light
how do I shut off Mr Coombs from this website. he is already gone from my DPR site, and that was from a while ago. The poor girls twitched or you did. Yea, blame the camera, blame You mr Coombs. Snapsy your next! I finally figured out your Horshak on DPR. Now your gone too
p.18 #7 · Z8 extremely unreliable/inconsistent AF in mildly low light
SCoombs wrote:
Ok, but for the most part using non subject recognition modes are working much more reliably in my testing. Not perfectly, but much more reliably.
Problem is I have no idea if your camera is performing at typical z8 standard or not. My own experience abide difference in subject and condition, has been very satisfactory. Thats pretty much all I can contribute at the moment.
p.18 #8 · Z8 extremely unreliable/inconsistent AF in mildly low light
To reach a definitive answer, the scientific method needs to be employed. That will involve an experimental design with standardized data acquisition criteria. Multiple test subjects (Z8) have to be evaluated under identical test conditions. That's the only way to obtain sufficient data to draw a meaningful and valid conclusion. It's simply not possible to make any valid determinations by using ad-hoc criteria, like posting in-focus photos and saying, "See! My camera works!"
Nikon isn't going to be interested in hearing from a single user about problems with their cameras. But a well-designed test that is replicated by a large number of users in a well-respected photography forum would be hard for them to ignore.
Having one person take the time to replicate tests under SCoombs' criteria would be a step in the right direction to validate or refute the existence of the problem in other Z8 cameras.
p.18 #9 · Z8 extremely unreliable/inconsistent AF in mildly low light
I was curious so I tried to replicate suteetat's conditions as closely as I could. I had to go wander around and go into the basement and find a corner somewhere without too much light streaming in but I finally managed to get to something similar. The best I could initially do was EV-1.
At EV-1, I was able to get the subject recognition to focus on the eye of this statue and other than motion blur in some photos (I did NOT use a tripod for this) all but maybe one or two of 19 were in focus, and even those were difficult to judge between camera shake vs lack of focus.
This is also a relatively small statue - about a foot tall - so depth of field is advantageous, but as can be seen from the more head-on shot there was definitely room to miss. How large is the statue from suteetat's photo? Is it of a similar size, or larger? I also had to zoom the lens to a longer focal length in order to get subject recognition to kick in. The eyes were just too small when I was in the ~60mm range.
I then grabbed a scarecrow I had to try to provide a larger target so I could use a wider focal length. I was able to find a slightly different spot for this, thanks to its larger size, so that I could exactly replicate the EV-2 condition. The focal length was also similar, at 52mm.
Head on, the subject recognition did struggle a bit more. It's hard to know how much of this may be from the fact that the eyes are not realistic looking human eyes. I was able to get most photos in focus again.
Swapping the scarecrow to a more oblique angle made a huge difference. I simply could not get the subject recognition to focus on it at this angle. I could either get it to focus when the subject recognition didn't kick in, or if it did kick in, it would hunt for a bit before giving up and going back to non-subject recognition AF.
Finally I was able to get it to focus in subject recognition by turning on d10 starlight view. I DID have d9 set to adjust for ease of viewing the entire time, but starlight view apparently gave it an extra boost it needed for subject recognition to work in these conditions. Nevertheless, it was struggling. I had to patiently wait for it to lock on and take photos and watch for it to lose focus and wait for it to reacquire. The hit rate paying attention to this was around 3/4, whereas if I'd been shooting without paying attention it would have been lower.
My conclusions, for what they're worth based on one test:
Down to EV-1 at f4 I can get the SR system to focus pretty reliably on inanimate objects with human features.
At EV-2 at f4 the subject recognition system struggles or fails to work on inanimate objects with human features, though this probably depends on the exact object. For instance, I also took a few of the St. Michael statue in a different position that yielded EV-1.7. I didn't share one here, but most were in focus even when it was struggling on the scarecrow.
Most notably, the system NEVER did the thing I'm showing it do with human subjects at EV4 where it displays a relatively confident AF lock on the front eye but backfocuses onto the other eye or something else altogether.
I would therefore conclude that inanimate object with human features may not be a good analog for demonstrating expected AF performance on human subjects.
p.18 #10 · Z8 extremely unreliable/inconsistent AF in mildly low light
snapsy wrote:
These are fantastic captures. I downloaded each of your YT videos and frame-stepped each to correlate the precise moment of capture (using the "r" buffer indicator changing to determine this) with the NEFs you supplied in the Google download link. These are your best examples yet of the camera outright misfocusing for what LV was indicating was steady in-focus. It seems clear from these samples that this EV 4 is outside the camera's range for consistent focus in this particular setup and subject.
After doing some more sleuthing/reading online regarding "Low Light AF" on the Z8/Z9 it's become clear to me that the OP's experience are more than anecdotal and not indicative of a faulty unit, a TLDR "reddit" with sublinks by way of example...
It's also becoming clear to me that the issue is clearly dou-fold/two-fold as there clearly is a contrast threshold also at play for the Z8/Z9 AF system as EVs lower, again, an example accounting...
<<
The focusing in the dark – well, if the object doesn’t move, it’s good, it can find focus in near-dark situations as long as the object doesn’t move. It’s impressive – you don’t see the thing with your eye, but through the viewfinder, you can see it like in a night vision. Then again, focusing on faces is still an issue – say people reading/speaking a speech in candlelight – it comes out soft, and the D5 takes care of that shot.
>>
It would be interesting to test the competition flagships with your setup and conditions, it might reveal a difference in how different Eye AF systems contend with not just "low-light human eye-detect" but "LOW-CONTRAST/low-light human eye detect". Onward!
_________________________
Methinks the OP's pursuit here for EV 4 Eye-AF is an important one in that there are clearly lots of shooters in this world trying to take pictures of their kids at home under existing lighting, or shooting dimly-lit weddings and receptions, or nighttime street, or a number of other, er, "normal" photographic pursuits. EV 4 is not some extreme rarity!
As for the, er, "well-meaning" OT posts of the world, a simple redirect reminding them of the subject-at-hand (read: EV 4 Low Light Human Eye AF) should be more-than-enough-of-a-response to keep the thread on-topic...well, IMHO. Ha!
p.18 #11 · Z8 extremely unreliable/inconsistent AF in mildly low light
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 modes - the camera had significant trouble focusing in AF-S for single point AF over the eye, which to me indicates the root issue here is insufficient PDAF sensitivity at these light levels for this particular subject.
In other words, the eye AF issue I'm showcasing is really a PDAF sensitivity issue. It manifests in eye AF since the size of the PDAF area employed by the subject tracking is a smallish portion of the eye, a portion that AF-S demonstrates focusing trouble with.
Here's the video. The cross-hatch pattern to the left of the mannequin is magnified and split-screen to show when the focus is hunting.
Time jumps:
0:00 AF-C 3.5EV
0:21 switch to 6.5EV, little to no hunting
0:35 switch back to 3.5EV
1:24 switch to AF-S, trouble focusing
2:06 switch to single-point AF
2:25 switch to wide-point AF without subject detection
2:35 switch back to single-point AF
2:52 switch back to eye-AF auto area
p.18 #13 · Z8 extremely unreliable/inconsistent AF in mildly low light
chatcher wrote:
Does enabling the AF-Assist Illuminator (AF-S) have any effect on these issues?
I have found the AF-Assist illuminator has given me a 100% hit rate. It works very well when it can be used. Unfortunately it can't be used in AF-C, which is what you need for a lot of stuff like event photography. It is also very noticeable so it is harder to use when trying to get candid shots of, say, a dance or whatever.
I'd definitely use it for portraits at an event to just ensure focus.
I think the question you ask is especially important actually, because in looking through old forum threads and reddit posts and articles online there are a LOT of professionals complaining not about the AF in low light, but about the fact that the old IR and red assist grids that are found on speedlights no longer work for the Z (and all brands') mirrorless cameras. Some have said in this thread that if this were really a problem we'd see a lot of professionals, wedding photographers, etc. complaining about it and the truth is that there have been a lot who have but they haven't phrased it as complaints about the AF: they've phrased it as complaints that their assist lights don't work anymore, which is making it hard for them to get shots at receptions and so forth.
p.18 #14 · Z8 extremely unreliable/inconsistent AF in mildly low light
SCoombs wrote:
… the fact that the old IR and red assist grids that are found on speedlights no longer work for the Z (and all brands') mirrorless cameras.
This has been one of my minor peeves with the Z system - that there are no new Speedlights, with mirrorless-compatible focus assist capabilities. I guess I’m old, because I find it hard to let go of all the stuff that’s gone out of style - tripods, flashes, remote releases, etc. Sure, camera improvements have made such things a little less important than they once were, but I still use them. And I get that Nikon doesn’t want to be in the flash business anymore. But I don’t like dealing with problems that were solved a long time ago. I like my Z9, but there are a few reasons I’m not ready to let go of my D780.
p.18 #15 · Z8 extremely unreliable/inconsistent AF in mildly low light
In the previous video I demonstrated how the Z8's eye AF is constantly hunting in low-light (3.5EV) conditions. In this next video I demonstrate the reason - it's the phase evaluation from the PDAF pixels that's driving the hunting. If we switch the camera to MF we can see the camera's phase evaluation via the onscreen rangefinder. I demonstrate how the rangefinder is constantly flickering in 3.5EV conditions, indicating how the phase detection is vacillating between "in focus" and "oof", even though the camera and subject are locked down and the lens is idle. I then open the lens up to a larger aperture and demonstrate how the phase detection stabilizes. This showcases how sensor noise from low-light conditions makes phase evaluation tougher for the camera to focus. It also demonstrates how Nikon's decision to focus stopped-down creates a handicap for Z cameras vs other MILCs that focus wide-open.
Note in this video I've switched to the left eye, to make it easier on the AF system.
While viewing move your mouse cursor away from YT's embedded player so that the overlay at the bottom goes away - otherwise it'll obstruct the rangefinder display at the bottom left of the LV feed.
p.18 #16 · Z8 extremely unreliable/inconsistent AF in mildly low light
While it is true that autofocusing at the shooting aperture (down to f/5.6) puts the Nikons at a disadvantage in low light assuming that you do want to shoot stopped down, it helps maintain a stable brightness of the viewfinder as the aperture is not changing between taking of shots and autofocusing. At least I found the Canon R mount cameras' viewfinder flickering highly disturbing in a similiar situation due to the camera switching between shooting aperture and wide open when viewing the EVF.
The second advantage of Nikon's approach is that it eliminates the inaccuracy due to focus shift between apertures (wide open to f/5.6).
Of course, allowing both options is something Nikon can consider including in future camera models or firmware updates. Personally I really appreciate the stable viewfinder.
p.18 #17 · Z8 extremely unreliable/inconsistent AF in mildly low light
ilkka_nissila wrote:
While it is true that autofocusing at the shooting aperture (down to f/5.6) puts the Nikons at a disadvantage in low light assuming that you do want to shoot stopped down, it helps maintain a stable brightness of the viewfinder as the aperture is not changing between taking of shots and autofocusing. At least I found the Canon R mount cameras' viewfinder flickering highly disturbing in a similiar situation due to the camera switching between shooting aperture and wide open when viewing the EVF.
The second advantage of Nikon's approach is that it eliminates the inaccuracy due to focus shift between apertures (wide open to f/5.6).
Of course, allowing both options is something Nikon can consider including in future camera models or firmware updates. Personally I really appreciate the stable viewfinder....Show more →
Sony has struck the best balance - the aperture focus behavior is selectable I set my Sony to always focus wide open long ago and forgot there was also an option to focus stopped-down, which is actually the default.
There should be a way for camera makers to work around the brightness changes during aperture movements but would require a bit of image processing.
p.18 #18 · Z8 extremely unreliable/inconsistent AF in mildly low light
chatcher wrote:
This has been one of my minor peeves with the Z system - that there are no new Speedlights, with mirrorless-compatible focus assist capabilities. I guess I’m old, because I find it hard to let go of all the stuff that’s gone out of style - tripods, flashes, remote releases, etc. Sure, camera improvements have made such things a little less important than they once were, but I still use them. And I get that Nikon doesn’t want to be in the flash business anymore. But I don’t like dealing with problems that were solved a long time ago. I like my Z9, but there are a few reasons I’m not ready to let go of my D780. ...Show more →
It's pathetic that the 'most advanced camera system' from Nikon forces you to use a slide rule to perform manual flash calculations. It's as if they expect everyone will just be content with paying $$$ for Nikon's fast glass, dialing up the ISO and shooting in ambient light.
From the late 80's onward, Nikon's film SLR and dSLR had speedlights that could handle this sort of thing automatically. The result was that everyone quickly forgot how to do flash calculations. Now what's old is new again and everyone has to learn to use Guide Numbers or they're left in the dark. Thanks, Nikon.
To get flash to work with the Z system you have to relearn how to use Guide Numbers or you're doomed to become a chimping strobist who works by trial and error.
I keep DSLR in the kit because I need flash support.
p.18 #19 · Z8 extremely unreliable/inconsistent AF in mildly low light
coralnut wrote:
It's pathetic that the 'most advanced camera system' from Nikon forces you to use a slide rule to perform manual flash calculations. It's as if they expect everyone will just be content with paying $$$ for Nikon's fast glass, dialing up the ISO and shooting in ambient light.
From the late 80's onward, Nikon's film SLR and dSLR had speedlights that could handle this sort of thing automatically. The result was that everyone quickly forgot how to do flash calculations. Now what's old is new again and everyone has to learn to use Guide Numbers or they're left in the dark. Thanks, Nikon.
To get flash to work with the Z system you have to relearn how to use Guide Numbers or you're doomed to become a chimping strobist who works by trial and error.
I keep DSLR in the kit because I need flash support....Show more →
Obviously I'm the one who started this discussion so I'm not without my issues with the system right now, but I will say that I think the thing about flash is largely true for all manufacturers. I don't think any of them make a flash for their mirrorless systems.
JG