Author Topic: lines in the blurred part of background  (Read 729 times)

JKoerner007

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Re: lines in the blurred part of background
« Reply #15 on: April 16, 2018, 16:56:51 »
I'm sure it would be possible to have VR ON during composing/focusing and OFF during the actual exposure, it should be just a matter of programming. Whether Nikon think this is a sensible thing to do is another matter.  :)

I find that VR SPORT with the 300/4 PF does work nicely also for faster shutter speeds (typically 1/500s to 1/1250s in my case with this lens); I would turn VR OFF at 1/1600s or faster.  Hand-held of this very lightweight tele is much easier in VR SPORT mode than VR OFF. But VR OFF may result in sharper pics (and perhaps fewer artifacts) in some circumstances.


Hmmm, I use VR Sport essentially all the time, even up to 1/5000.

Indeed, it does help frame the capture, and I've never seen it blow the background out like what's described.

I've read that early versions of the 300 PF exhibit this effect, not late ones.

Another variable is the D850 and "its" compatibility with the 300 PF.

I use the D500, and I honestly think the D500 was "made" for it. I have got 'perfect' bokeh with the 300 PF in "Sport" mode from 1/1600 to 1/5000.

Here are some examples ... all very small birds ... all images cropped to some degree. Still decent bokeh:

Frank Fremerey

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Re: lines in the blurred part of background
« Reply #16 on: April 16, 2018, 17:11:07 »
@John: All of your pictures exhibit large, non repeating structures far away. All trouble is caused by repeating structures like stones or grass or brick and as I recall only a certain granularity. It is an interference with these kind of structures and it is also exhibited with the D500.

JKoerner007

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Re: lines in the blurred part of background
« Reply #17 on: April 16, 2018, 17:21:10 »
@John: All of your pictures exhibit large, non repeating structures far away. All trouble is caused by repeating structures like stones or grass or brick and as I recall only a certain granularity. It is an interference with these kind of structures and it is also exhibited with the D500.

Interesting, Frank, thanks.

I do generally tried to avoid 'backgrounds' at all with wildlife, but sometimes that's not possible.

That said, I've also shot the D500/300PF combo, with VR-Sport mode on, with 'repeating' or 'granular' backgrounds, when necessary (at fairly-high shutter-speeds also)  as below.
(Still have yet to see the described phenomenon ... and thankful for it!)

golunvolo

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Re: lines in the blurred part of background
« Reply #18 on: April 16, 2018, 21:49:50 »
The VR sampling frequency is 1000Hz (according to a VR article by Thom Hogan), which means that the highest signal frequency that can be sampled is 500 Hz  - 1/500 s according to the Nyquist Theorem. However we do not know which countermeasures Nikon has put in place to avoid that VR goes haywire beyond that shutter speed. In my own experience the VR on the 300 PF works well up to 1/500 sec. Beyond that it would not help keeping the exposure steady but I find that the Sports Mode is a great help for aiming though the viewfinder and keeping focus point on the target; I have hardly seen any detrimental effects up to 1/1000 sec. At 1/1250 sec, I have seen signs of background artifacts, although nothing horrible. at 1/1600 second I would likely want to turn it off. This is all handheld with the D7100 and lens collar mounted, other bodies could perhaps respond differently both technically and with respect to physical interactions.

I do not think I have ever seen bokeh effects that can be ascribed to the phase fresnel lens element in any normal captures, however if one really go for it one can create a nice phase fresnel ghost in IR as in this false color rendition:


NIKON D40X IR-720nm, AFS 300mm f/4 PF VR  @ f/4, 1/400, ISO 100

   Love this. You did get it!

Řivind Třien

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Re: lines in the blurred part of background
« Reply #19 on: April 16, 2018, 21:59:33 »
Thanks for the kind comment Paco.
Řivind Třien

Řivind Třien

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Re: lines in the blurred part of background
« Reply #20 on: April 16, 2018, 23:17:25 »
I'm sure it would be possible to have VR ON during composing/focusing and OFF during the actual exposure, it should be just a matter of programming. Whether Nikon think this is a sensible thing to do is another matter.  :)
That is a god point, thanks for the reminder. The viewfinder phase and the exposure phase can be separate, and in many (most/all ?) cases the VR optical element resets to center position between these phases.

Before blaming the VR, the optical quality of the air (heat waves etc.) can also cause bokeh artifacts and degradation of resolution at the right subject to background distance ratios. Here is an example of a frame I did not use from last years Iditarod start. VR was off at 1/1250 sec shutter speed, but there were strong inversion layers down at the river as the air was warming up from a night at -33°C:


 
Auto-focus (AF-C mode, 9-point dynamic) was also confused; the focus point was at the yellow harness of the second dog from the front, but the plane of focus is at the cameraman at the right.
Řivind Třien

richardHaw

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Re: lines in the blurred part of background
« Reply #21 on: April 17, 2018, 03:23:27 »
 :o :o :o