Author Topic: 4000 X 6000 Dx Megapixels, AF help & comments  (Read 3561 times)

Matthew Currie

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Re: 4000 X 6000 Dx Megapixels, AF help & comments
« Reply #15 on: March 23, 2017, 16:42:19 »
I would just add that my D7100 appears to be fine, and with the 18-140 lens it came with it was always nice and sharp.  I've used a number of different lenses on it and most appear to be right on without adjustment.  However, the two I've had to adjust were the 50/1.4D, which my wife got years ago for an F100 and which was always disappointing, and the 16-85 DX zoom, which I bought used.  I suspect that perhaps that 16-85, aside from not being as crisp as the 18-140, might be a little more problematic in tuning as well.  A quick and dirty indoor tune came out with considerable improvement at +5, but it is still a little variable depending on distance and zoom, and never killingly sharp.   At some point I'll do a more thorough, outdoor-lit test, but I suspect that comes pretty close.  The 50/1.4 has become rather nice with its new calibration, after years of neglect owing to its disappointing softness.

I'm guessing here, but imagine that the very high acuity of the D7100 might make tiny focus errors show up more readily, at least when you pixel peep, and that some lenses, of which the 16-85 might be one, may just never satisfy at all distances and focal lengths.  But in this case I'm much more inclined to blame the lens, which visibly back focused on the D3200 as well as on the D7100.  Almost every AF lens I've tried on the D7100 has been close enough not to calibrate, and the MF lenses appear to be correctly focused when the dot says they are.  Fortunately, it seems a good bit easier to confirm good focus than to fix it when it's bad. 

Akira's observation about AFC versus AFS seems interesting, and worth further investigation.  On the D3200, I'm pretty sure the opposite applied, as it's noted in the instructions that focus priority in AFC is relaxed and there's an implication, as usual for Nikon never quantified, that the focus itself is a little sloppier.  It's very hard to judge, especially as lenses themselves vary, but it seems, looking at the focus confirmation dot, that the area considered "good enough" is a little wider.  But if the area is the same, I'd expect AFC to work a little better because it keeps adjusting after the initial hit, rather than stopping as soon as it finds that "good enough" spot. 

Peter Forsell

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Re: 4000 X 6000 Dx Megapixels, AF help & comments
« Reply #16 on: March 24, 2017, 11:21:00 »
... Akira's observation about AFC versus AFS seems interesting, and worth further investigation...

@Matthew Currie
Can you provide link to the text re AFC vs AFS please, I didn't find in this thread and I'd like to read.

Akira

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Re: 4000 X 6000 Dx Megapixels, AF help & comments
« Reply #17 on: March 24, 2017, 12:58:30 »
@Matthew Currie
Can you provide link to the text re AFC vs AFS please, I didn't find in this thread and I'd like to read.

Peter, please refer to the post #9 of this thread.

Also, you may want to refer to this thread, too.

http://nikongear.net/revival/index.php/topic,5542.msg88782.html#msg88782

That said, my personal experience (better hit rate of AF-C than that of AF-S) might be because of my shaky body.   :o
"The eye is blind if the mind is absent." - Confucius

"Limitation is inspiration." - Akira

Peter Forsell

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Re: 4000 X 6000 Dx Megapixels, AF help & comments
« Reply #18 on: March 24, 2017, 18:29:34 »
Thank you, good read.

Matthew Currie

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Re: 4000 X 6000 Dx Megapixels, AF help & comments
« Reply #19 on: March 26, 2017, 00:03:15 »
@Matthew Currie
Can you provide link to the text re AFC vs AFS please, I didn't find in this thread and I'd like to read.

The following passage is found on Page 39 of the D3200 manual: "In AF-C mode or when continuous servo AF is selected in AF-A mode, the camera gives higher priority to focus response (has a wider focus range) than in AF-S mode, and the shutter may be released before the in-focus indicator is displayed."

In the corresponding section of the D7100 manual this passage does not appear.  The D3200 manual, as expected, is vague about the extent of this difference.


Matthew Currie

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Re: 4000 X 6000 Dx Megapixels, AF help & comments
« Reply #20 on: March 26, 2017, 00:05:18 »
The following passage is found on Page 39 of the D3200 manual: "In AF-C mode or when continuous servo AF is selected in AF-A mode, the camera gives higher priority to focus response (has a wider focus range) than in AF-S mode, and the shutter may be released before the in-focus indicator is displayed."

In the corresponding section of the D7100 manual this passage does not appear.  The D3200 manual, as expected, is vague about the extent of this difference.

added note:  this is the PDF manual.  Anyone owning one of these low end cameras should be aware that the printed manual provided is shamefully abridged, and should download the PDF from the accompanying disk or from Nikon's web site.

Steven P.

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Re: 4000 X 6000 Dx Megapixels, AF help & comments
« Reply #21 on: March 27, 2017, 17:14:00 »
Thanks to all, again. For anyone down the road with similar cameras with similar issues, I hope this will help.

My D7100 with medium to longer lenses, AF focuses usually quite well, especially with a clear, defining target. When I creep into 24mm & shorter focal ranges, the issue manifests.

I'm a victim of old film camera habits. I usually single click at base ISO using the center AF point, only. This worked well until the D7100. A year or so prior, I bought a Refurb, D5200 & my old habits still worked fairly well. I liked the cropping room of 24mp, higher ISO performance. My idea of the D7100 was the easier ability to use older MF glass & an in body focus motor. The other attraction was a camera body to actually grip with all four fingers.

I played a lot with my 16-85VR, focus testing &  fun shooting. 85mm is fine. 16mm was pretty much disappointing. I turned off Vibration Reduction & images improved a great deal. Tripod mounting helped even more. A sub par protective filter, (Name brand filter/But not so good coatings,) was another culprit.

Say, at 16mm with a group of small detailed objects 8-10 feet away, it still misses focus when everything in the frame is small. (All the detail is less than the coverage of any single AF point.) AF-A/AF-C works better especially when Auto or 3D mode is used, but it's not a magic fix.

What helped more was doing some homework & learning the lens's hyperfocal distance and using the correct aperture/distance, manually. My 3rd party 12-24 is rather simple. (7 feet & F4 is easy to remember for 12mm.) The 16-85 is a bit more complicated. I almost wanted to inkjet a small cheat sheet & clear tape it to the lens body but I know sticky tape adhesive on gear or even a carry sack isn't a good idea.

All is improving, as I continue to move foreword.

Thanks Again,
Steve
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