NikonGear'23
Gear Talk => Lens Talk => Topic started by: Frode on August 14, 2018, 21:03:24
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My sample is tack sharp when using the center AF- point. No need for fine- tuning there.
However, when using any of the outer AF points (other than the 15 crossensors in the senter), I get soft focus (no matter what side). Need about -15 when using theese in order to get OK sharpness.
Been told that this is normal due to the strong vignetting.
Experience/thoughts?
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Vignetting should affect image brightness, not sharpness. Field curvature and/or focus shift on stopping down maybe?
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Vignetting should affect image brightness, not sharpness. Field curvature and/or focus shift on stopping down maybe?
I have no idea, Roland, but field curvature sounds logic...? Used the lens wide open only.
Hmm, I miss the opportunity to compose in the viewfinder instead of cropping afterwards.
With the AFS 50 1.8G and AFS 85 1.8G, all focus points works just fine. With AFS 400 2.8 VR all but the last row at both ends works fine. Last rows are a bit soft.
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Post a couple of images, then it's maybe possible to tell what is going on ;)
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Did at non- scientific test of both my AFS 50 1.8G and AFS 20 1.8G. First out, the 50mm.
AFS 50 1.8G:
4927, AF center, 1.8
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AFS 50 1.8G
4928, AF left, 1.8
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AFS 50 1.8G
4929, AF right, 1.8
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AFS 50 1.8G
4930, AF right, 2.5
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AFS 50 1.8G
4931, AF left, 2.5
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AFS 20 1.8G
4974, AF center, 1.8
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AFS 20 1.8G
4975, AF left, 1.8
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AFS 20 1.8G
4976, AF right, 1.8
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AFS 20 1.8G
4979, AF left, 5.6
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AFS 20 1.8G
4981, AF right, 5.6
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Had to stop down the 20mm to 5.6 in order to get ok sharpens, f/4 was not sharp enough.
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Are these crops? if not, you must be almost at closest distance, with what follows of implications,,,
Where was the AF-focus points in the images? I get its left and right, but where exactly,,, ;)
Do you notice the field curvature and vignetting?
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No, not normal. I get very consistent AF with this lens.
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Are these crops? if not, you must be almost at closest distance, with what follows of implications,,,
Where was the AF-focus points in the images? I get its left and right, but where exactly,,, ;)
Do you notice the field curvature and vignetting?
No crops, not at THE closest distance, but not far from either.
Colored the area where I focused - good point, Erik ;D.
I dont know what I notice anymore, must say I'm a bit frustrated regarding the D850 and its AF combined with MY lenses. It`s hit and miss. Can't say that I trust these combinations, would NEVER do a wedding the way things are right now.
Thank you for your response.
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No, not normal. I get very consistent AF with this lens.
Hmm, not what I wanted to hear.... :-[
Raptor- season closing in, but the way tings are right now, I'm considering trading in my Nikon- stuff. I really love to photograph, especially when out in the nature, but I'm so fed up spending time with gear (expensive - for me any way) that doesn't work as it should. I'm absolutely NOT impressed with D850 and its AF (with my lenses :-).
Thank you for your response :-).
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D850 + AFS 20 1.8G, AF- S, single AF mode:
Looks like the AF coverage of a single AF point is MUCH larger than it appears in the viewfinder. Pictures shows where I got AF- lock.
About the same result with the other AF points.
Other D850 users, do you have the same "performance"?!
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You need to us better AF targets for such a test, and not that close up.
And yes the sensors are wider/larger than indicated in the viewfinder.
They are also different kinds, cross and straight.
A single black line is also a very bad target for AF Sensors,,,
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You need to us better AF targets for such a test, and not that close up.
And yes the sensors are wider/larger than indicated in the viewfinder.
They are also different kinds, cross and straight.
A single black line is also a very bad target for AF Sensors,,,
Thank you again, Erik.
Regarding AF targets, I looked up Nikon and found that such "easy" targets was ok to use (?). Se links below. For the record, I focused through the viewfinder :-).
https://nps.nikonimaging.com/technical_solutions/d4s_tips/af_fine-tuning/
https://nps.nikonimaging.com/technical_solutions/d850_tips/useful/auto_af_fine-tuning/
The AF sensors were a bit bigger than they appear in the viewfinder with my former D4s also, but not THAT big.
Yes, with my lenses (1.8 and 2.8 lenses) the three middle rows and last two in both ends (left/right) are cross sensors, reading vertical AND horizontal lines. Other just horizontal lines. Took it into account when performing the "test" :).
Also, got the same result when focusing further away from the target.
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The sensors don't "read" lines, they see contrast.
I don't think that your thin lines are equal to the broad fat lines of Nikons sugessted.
Didn't you use AF? You state: "focused through the viewfinder" ? :o
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Remember the "invisible" af sensors:
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The sensors don't "read" lines, they see contrast.
I don't think that your thin lines are equal to the broad fat lines of Nikons sugessted.
Didn't you use AF? You state: "focused through the viewfinder" ? :o
You’re probably right about my target, Erik.
Yes, it’s the contrast the sensors see.
My bad, yes I used AF (not via liveview :).
Went to my local store today; my copy of the 20mm was soft at the edges compared to a sample they had. Bought a new one. Much better.
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Remember the "invisible" af sensors:
Thank you :),
Yes, it might be the «invisible» AF sensors that makes the «active» AF area somewhat bigger (?).
Wish I could turn them of when needed, though.
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I dont know what I notice anymore, must say I'm a bit frustrated regarding the D850 and its AF combined with MY lenses. It`s hit and miss. Can't say that I trust these combinations, would NEVER do a wedding the way things are right now.
I don't suppose it would be possible to have Nikon service take a look at your camera and lens?
Regarding the D850, the AF on moving subjects is slightly disappointing with my fast primes (compared to D5) but very good on stationary subjects such as portraits. With the D5 the AF results make me speechless in many cases. The D850 is very sensitive and good in focusing but somehow with moving subjects I tend to get less consistent results than with the D5.
AF tends to be better with longer focal lengths than shorter ones. But I've been very pleased with the 20/1.8 AF-S's autofocus in general (using on D810, D5 and D850). It's fast and consistent in focusing, and much much better than the 14-24/2.8 or 24/1.4. Aesthetically I prefer the 24mm f/1.4's "look" but the 20mm for AF consistency.
I can do some further experimentation with the 20mm f/1.8 and D850. How low lighting conditions are you expecting to use yours in? In very low light there can be additional variation in AF results. I can try in similar conditions.
I think for formal AF tests I would preferably use the kind of distance range where your normal shots are in. E.g. with 20mm I would use a 2m distance to target, maybe 3m.
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If you use single point, the system uses a single point, the invisible points are only used when a larger area is selected. The in between points are displayed in the viewfinder as dots if you select 9-point dynamic area, for example.
In practice the AF receptive fields in multi-cam 20k are much smaller than in the multi-cam 3500.
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The sensors don't "read" lines, they see contrast.
I don't think that your thin lines are equal to the broad fat lines of Nikons sugessted.
Didn't you use AF? You state: "focused through the viewfinder" ? :o
Phase detection in normal mode and contrast in live view.
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Yes they have nice names for it :o
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I don't suppose it would be possible to have Nikon service take a look at your camera and lens?
Regarding the D850, the AF on moving subjects is slightly disappointing with my fast primes (compared to D5) but very good on stationary subjects such as portraits. With the D5 the AF results make me speechless in many cases. The D850 is very sensitive and good in focusing but somehow with moving subjects I tend to get less consistent results than with the D5.
AF tends to be better with longer focal lengths than shorter ones. But I've been very pleased with the 20/1.8 AF-S's autofocus in general (using on D810, D5 and D850). It's fast and consistent in focusing, and much much better than the 14-24/2.8 or 24/1.4. Aesthetically I prefer the 24mm f/1.4's "look" but the 20mm for AF consistency.
I can do some further experimentation with the 20mm f/1.8 and D850. How low lighting conditions are you expecting to use yours in? In very low light there can be additional variation in AF results. I can try in similar conditions.
I think for formal AF tests I would preferably use the kind of distance range where your normal shots are in. E.g. with 20mm I would use a 2m distance to target, maybe 3m.
Thank you, Ilkka :-)
Yes, it might be that I need to send it in (recalibrate and re- adjust the AF points?). Still like to hope that there's "a way out"....
I dont expect the D850 to have the same performance as the D5 regarding AF, but hoped it would be as good as the D4s (don't feel I can "trust" the camera yet).
Usually I use my gear in good lighting conditions (fast shutter speed and low iso), but worst case scenario would be like indoor (dark outside), tungsten light, portraits of people (almost static) and exposures like 1/250, f/1.8- 2 and iso 6400- 12800. Not often though. In such conditions I don't have to high expectations, but would like to feel a bit more secure on how the camera works (AF).
I like to use my 20mm relatively close up to my main subjects (in order to get a view of the environment also, though often isolated using a large aperture like f/1.8- 2.8). Main subject is often a person or animal/bird. Distance often between 1- 3 meters.
The way I've used my Nikons so far: if cross sensor af points are being used then I aim the af- sensor at area where there's vertical lines of contrast. When using the other af- sensors I go for horizontal lines of contrast.
With my former D4s I found that the coverage of the af sensors was 1/3 outside of the visible af point, at all four directions. With the D850 (so far...), it looks like it covers a lot more space outside the af sensor, making it hard to know what to expect to be in focus. I feel like I have to check every photo in order to see if it`s in focus or not. I felt I could trust my D4s a LOT more.
Looking forward to hopefully "trust" the camera again, it`s a great camera in many ways!
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If you use single point, the system uses a single point, the invisible points are only used when a larger area is selected. The in between points are displayed in the viewfinder as dots if you select 9-point dynamic area, for example.
In practice the AF receptive fields in multi-cam 20k are much smaller than in the multi-cam 3500.
Hmmm, I've got to get my hands on a better AF target and do a new test, because so far my impression is that the fields are MUCH bigger with my D850 compared to my former D4s.
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Hmmm, I've got to get my hands on a better AF target and do a new test, because so far my impression is that the fields are MUCH bigger with my D850 compared to my former D4s.
This doesn't sound right. I've found with the D810 and earlier cameras that when pointing a single sensor at a face in whole body portrait, that the camera would often focus on the backlit hair instead of the eye that I pointed the sensor at. This doesn't happen with the D5; I get very precise focusing on the face and the sensitivity of the AF sensor doesn't extend to the hair. In fact I can focus on the cheek's imperfections and it just locks on and holds focus. The D850 is a bit of a mystery as it doesn't do quite as well in tracking an approaching subject though it seems the AF sensor has similar sensitivity and characteristics. It's a bit like the camera lacked the power to do as fast tracking of a moving subject as effectively.
But the sensitive field of the individual sensors in the D850 in single point mode should be much narrower than on a D4s or D810.
What could be causing the impression that you're getting is the fact that the camera can see detail even in white surface if it has any structure to it, it doesn't need the line to focus based on, just some low-contrast structure (surface imperfections) can be enough. Of course high contrast detail is better but it can focus on relatively low contrast details also.
I generally point the single sensor on an eye but if I use D9, I often just point the primary point on the cheek, and it can hold focus very well without being attracted to the hair around the face.
Edit: I am just reviewing photos made with the 105/1.4 and D850 and I find that almost perfect focus when I was using 3D Tracking (with face priority) and this is really a positive surprise. So, 3D tracking and moving subjects, and single point or D9 on static subjects works extremely well, but for some reason I get inconsistent results with single point and D9 on faster approaching subjects. I should probably stop complaining and learn to use the camera. :-)
(Sorry for getting off-track. I will investigate the 20/1.8 this coming weekend.)
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The way I see it my D850 does seem to have about the same "problem" as the D810 (focusing on the face = sharp on backlit hair). Though, I must do some further testing in order to be certain. Suspect user error (af point to big compared to the contrast area it was pointed towards).
Regarding tracking compared to D5 (or any one digit bodies) other bodies do seem to lack some "juice". That be cameras like D700 (vs D3) and D810 (vs D4/s). In my opinion.
I tried to focus on the white area on the target used earlier (white paper with a black line), but it didn't lock until it got closer to the line. Non variable in structure/contrast in the white as far as I can see. Against a black cover (notebook) with some fine structure it locked though.
As far as I can remember the size of the af sensor in the viewfinder was bigger with my D4s compared to the D850 (?). In that regard the sensitive field might be narrower?
Hmm, regarding focus on relatively low contrast detail, I wonder if I have to high expectations? Can you describe what what you consider low contrast detail?
I`ve had good experience with D9 (blocked shot AF response set to 2) when photographing kids playing football (soccer) with my AFS 85 1.8 (yes, not far from the field :-).
Yesterday evening (low light) I found that the two columns at both sides, which according to Nikon are cross sensors, are clearly more precise when pointed at horizontal lines of contrast compared to vertical. Yes, they do react at vertical lines, but compared to the three center columns with cross sensors, they clearly hunted where as the center sensors didn't hunt at all (4EV vs 3EV?). The outer points locked focus when pointed at horizontal lines. Same with the other four columns with "standard" focus points (black ones - which didn't lock focus at all when pointed at vertical lines of contrast).
Please dont be sorry for getting off- track, always interesting to read about others experiences :).
I should probably be the one who should stop complaining and learn to use the camera :). Working on it..... :)
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Doing some more testing today (using my last summer vacation days.....) and I'm leaning toward the assumption that the camera needs to be calibrated (phase detect sensor alignment problem). Will send it in.