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Author Topic: Do we have more pixels than we ever needed?  (Read 14075 times)

Tim Lookingbill

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Re: Do we sit the same distance from our ever bigger video screens?
« Reply #40 on: March 27, 2015, 12:58:42 pm »

Having room for such a screen is not the issue;  I am betting that video on a 110" screen (280cm: what happened to the metric system in Australia?!) will be viewed from a distance of at least five feet (150cm) at which range 4K UHD will likely have a visible advantage over current HD, at least to sober viewers, but 8K will have no further advantage.

I do not think that a bit of curving will change that much; that reduces the oblique viewing of the edges of the screen, but still makes the angle between center and sides too wide for comfort if you sit less than one picture height from the screen.

But I am happy for chasers of big spec numbers to drive down the cost of devices that could be geninely useful for displaying digital still images.  The day will come when some galleries are truly digital, displaying photographs on such devices, with more DR than any printer can dream of.

I got the recent AVSforum newsletter that shows this setup...

http://www.avsforum.com/forum/139-display-calibration/1904321-colorimetry-research-cr-100-cr-250-experience-thread.html

I wonder how many can afford that setup and whether there's a sustainable market for such huge screens. Good grief they put more effort and money toward viewing content with such expensive calibration routines than we photographers who create content. Something's upside down here.
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BJL

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Re: Do we sit the same distance from our ever bigger video screens?
« Reply #41 on: March 27, 2015, 02:06:26 pm »

I got the recent AVSforum newsletter that shows this setup...

http://www.avsforum.com/forum/139-display-calibration/1904321-colorimetry-research-cr-100-cr-250-experience-thread.html

I wonder how many can afford that setup and whether there's a sustainable market for such huge screens. ...
And yet the first thing I note is that the comfy chairs are far more than one screen _width_ from the screen, and so barely able to distinguish between HD and 4K, let alone between 4K and 8K!  So it is probably a good thing that they are obsessing about color accuracy rather than definition*.


* At least video people know the difference between definition (number of lines or pixels or such) and resolution (lines per mm, pixels per mm, etc.); I wish still photographers would use that terminology more often.
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Tim Lookingbill

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Re: Do we sit the same distance from our ever bigger video screens?
« Reply #42 on: March 27, 2015, 03:03:42 pm »

And yet the first thing I note is that the comfy chairs are far more than one screen _width_ from the screen, and so barely able to distinguish between HD and 4K, let alone between 4K and 8K!  So it is probably a good thing that they are obsessing about color accuracy rather than definition*.


* At least video people know the difference between definition (number of lines or pixels or such) and resolution (lines per mm, pixels per mm, etc.); I wish still photographers would use that terminology more often.

I'm a definer, not a resoluter. ;D

In fact I had to use a third of my 6MP Pentax K100D DSLR resolution (by switching to 35mm focal length & cropping in ACR) to capture how the definition of my 32in/720p Samsung HDTV actually looks to my eyes viewing from 7ft. in order to carefully output sharpen (requiring several back & forth iterations) for downsampling to 700 pixels wide and still retain the definition as it appears in this thread.

My camera's AF kept micro-focusing on the teeny-tiny frickin' pixel grid of the HDTV I couldn't see with my eyes instead of the contrasted edges of the actual scene. Downsampling can work wonders for web viewing in this instance.
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Diego Pigozzo

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Re: Do we have more pixels than we ever needed?
« Reply #43 on: March 27, 2015, 05:43:19 pm »

But can you show or can anyone determine if the gargantuan data stream of packets from one with a "Power Bandwidth" provider such as dpreview is slowing other smaller sites?

I highly doubt that a single entity can perform such determination, since multiple systems are involved in the data transfert between you and dpreview/smaller-site.

But must be kept in mind that the "net neutrality myth" is not about "site speed" but "data packet speed", which means that to have a "net neutrality" all data packets are equals.
So if dpreview has the 1000x output bandwidth of the smaller site, dpreview will always go faster.

To be clear, "net neutrality" is very much like speed limits on a public road: all vehicle cannot go faster.
But a delivery business like FedEx will always use more road than me. no matter what.

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dreed

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Re: Do we have more pixels than we ever needed?
« Reply #44 on: March 30, 2015, 04:41:33 am »

We have been watching 600 to 800 lines of vertical resolution for half a century without complaints. That is the real resolution of 35mm movie projection in a good theatre.

http://www.motionfx.gr/files/35mm_resolution_english.pdf

I would love to see this test repeated as it was done over 10 years ago and before there was a rather large upgrading of projection equipment to handle 3D, 4K, etc.
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Diego Pigozzo

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Re: Do we have more pixels than we ever needed?
« Reply #45 on: March 30, 2015, 04:46:24 am »

I would love to see this test repeated as it was done over 10 years ago and before there was a rather large upgrading of projection equipment to handle 3D, 4K, etc.

I think we would have a result very much correlated with the relative vs absolute pitch, that is very few people would recognize the higher resolution frame when showed alone but many would see the difference between a high resolution and e low resolution frame.
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hjulenissen

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Re: Do we have more pixels than we ever needed?
« Reply #46 on: March 30, 2015, 04:58:17 am »

...that is very few people would recognize the higher resolution frame when showed alone but many would see the difference between a high resolution and e low resolution frame.
For the sake of "progressing science", side-by-sides are valuable.

For the sake of predicting what quality people will be able to appreciate? If one can appreciate 4k (over HD) only in a frozen side-by-side, then it seems safe to assume that one does not need 4k for regular viewing (in that particular setting)?

-h
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Diego Pigozzo

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Re: Do we have more pixels than we ever needed?
« Reply #47 on: March 30, 2015, 05:01:45 am »

For the sake of "progressing science", side-by-sides are valuable.

For the sake of predicting what quality people will be able to appreciate? If one can appreciate 4k (over HD) only in a frozen side-by-side, then it seems safe to assume that one does not need 4k for regular viewing (in that particular setting)?

-h

I agree with you: as I early said, higher resolution in movies is physiologically useless.
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jjj

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Re: Do we have more pixels than we ever needed?
« Reply #48 on: April 01, 2015, 01:44:07 am »

A few years back, a couple produced a movie about a husband and wife that were lost at sea while scuba diving on a dive trip when the dive boat miscounted and left the area, accidently leaving them there to die.  I can't remember the name of the movie.  It was shot on a Sony PD150 Standard Def NTSC DVCam camcorder.  It had a pretty broad theater release and was fairly successful as I recall.  Standard Def DVCam would be 720x480.
Open Water was the film. Cleverly done.
The reason they used the lo-fi camera was for aesthetic reasons. It looked rubbish on a big screen if talking technically, but it conveyed the story well - which was the point. The thing with film/video is that picture quality can be dire, but if the sound is spot on then it will 'look' great. However beautifully shot footage with duff sound will seem awful.

The Richard Linklater film, Tape was also shot on on a camcorder. As was the very influential Timecode, the cameras for which were bought by the director Mike Figgis from consumer electronic shops on Tottenham Court Road in London.
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jjj

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Re: Do we have more pixels than we ever needed?
« Reply #49 on: April 01, 2015, 01:54:26 am »

Indeed: as I understand it, our fine visual resolution depends in part on using saccade to detect edges, and that ability is at its peak for the detection of high contrast edges, leading to the peak angular resolution as measured with eye charts.

Moving images do not allow this, which is one reason that we have distinctly less resolution of moving images than of stills: note how bad the resolution looks on still frame grabs compared to the moving image they are grabbed from.

That is why I am betting that the difference between 4K and 8K video will only be noticed:
a) When reading the fine print at the tail end of movie credits.
b) In Warholesque movies with long still shots of eye charts and other finely detailed, high contrast subject matter.
c) When used to display still images and then viewing them from a distance of about half or less the width of the screen.
Moving images look poor quality as screen grabs as they are deliberately shot at low shutter speeds to give a smooth image.
If you shoot at higher shutter speeds and at the same frame rate, then the sharper frame image makes for a staccato look of moving subjects. Famously used during the beach scenes in Saving Private Ryan or typically when Zombies are chasing someone. So it's not wise to bet on things based on false comparisons between stills and video.  ;)
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Petrus

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Re: Do we have more pixels than we ever needed?
« Reply #50 on: April 01, 2015, 05:10:56 am »

Moving images look poor quality as screen grabs as they are deliberately shot at low shutter speeds to give a smooth image.
If you shoot at higher shutter speeds and at the same frame rate, then the sharper frame image makes for a staccato look of moving subjects. Famously used during the beach scenes in Saving Private Ryan or typically when Zombies are chasing someone. So it's not wise to bet on things based on false comparisons between stills and video.  ;)

In all honesty regular video frames are bad compared to same resolution stills. Besides the usual long shutter speed movement blur, there are 2 more reasons: Even normal HD has only half or one fourth of the color resolution compared to luminance, thus color resolution for typical 4:2:0 HD video is only 960x510 pixels. Only top tier professional video cameras can shoot 4:4:4 with full amount of color pixels, but even that is not distributed at full color resolution, because of the saved bandwidth and because it does not mattar much with a moving image.* Second reason is the extremely efficient compression methods used with video, typically delivery formats are 5% of the original data stream, often even less.

*) eye is much more demanding what comes to luminance, thus we are actually watching TV and videos with advertised resolution B&W with an overlay of half resolution color layer. It is also worth remembering that 35mm movie projection in a good theatre has the resolution of only 600-800 horizontal lines, less than HD video.
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hjulenissen

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Re: Do we have more pixels than we ever needed?
« Reply #51 on: April 01, 2015, 06:24:26 am »

In all honesty regular video frames are bad compared to same resolution stills. Besides the usual long shutter speed movement blur, there are 2 more reasons: Even normal HD has only half or one fourth of the color resolution compared to luminance, thus color resolution for typical 4:2:0 HD video is only 960x510 pixels. Only top tier professional video cameras can shoot 4:4:4 with full amount of color pixels, but even that is not distributed at full color resolution, because of the saved bandwidth and because it does not mattar much with a moving image.*
So video throws out information that matters little perceptually (or never was there in the first place, or cannot be recreated using common display tech). Why is that a problem? The Bayer CFA does something similar for cameras, so does JPEG still-image compression (and to a degree, chroma noise reduction).
Quote
Second reason is the extremely efficient compression methods used with video, typically delivery formats are 5% of the original data stream, often even less.
Again, video does its best to provide perceptually good results at minimum bandwidth cost. Since two video frames are often very similar, it only makes sense to exploit this in compression (for many but not all applications).

I do agree that one should be careful about re-using perceptual results from video perception to still images.

While it has been mentioned that our spatial resolution is effectively "less" for moving images than still-images, there is this issue of aliasing. If your camera/scaler/... creates aliasing, it can create annoying moving artifacts in video that moves (often counter to real movement). In still images, the same amount of aliasing can be acceptable. Thus, I think that video processing equipment tends to sacrifice some sharpness in order to reduce visible artifacts, while still-image equipment might let through more ("fake detail") aliasing. If you are displaying your 80MP images on your 4k LCD tv using the built-in scaling, results may or may not be optimal...

-k
« Last Edit: April 01, 2015, 06:36:23 am by hjulenissen »
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Diego Pigozzo

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Re: Do we have more pixels than we ever needed?
« Reply #52 on: April 01, 2015, 06:31:19 am »

Why is that a problem?

That's not a problem, but is a fact that a still image contains more information that a movie frame, no matter what the movie frame resolution is.
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hjulenissen

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Re: Do we have more pixels than we ever needed?
« Reply #53 on: April 01, 2015, 06:47:26 am »

That's not a problem, but is a fact that a still image contains more information that a movie frame, no matter what the movie frame resolution is.
Not sure if that is a "fact", but I'd be willing to accept that your typical video stream allocates less bits per frame than your typical still-image file.

"Information" is a relatively well-defined concept, but what we are interested in here is perceptual quality. Perceptual quality correlates poorly with information, especially when comparing two different concepts such as video streams and stills.

My point is that even though 4k video will have 2x2 downsampled chroma, what does it matter if we are unable to see the loss of quality for the wast majority of content (probably less for 4k than 1080p).

-h
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Diego Pigozzo

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Re: Do we have more pixels than we ever needed?
« Reply #54 on: April 01, 2015, 07:40:20 am »


My point is that even though 4k video will have 2x2 downsampled chroma, what does it matter if we are unable to see the loss of quality for the wast majority of content (probably less for 4k than 1080p).

That's my point too.
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Colorado David

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Re: Do we have more pixels than we ever needed?
« Reply #55 on: April 01, 2015, 02:21:30 pm »

Open Water was the film. Cleverly done.
The reason they used the lo-fi camera was for aesthetic reasons. It looked rubbish on a big screen if talking technically, but it conveyed the story well - which was the point. The thing with film/video is that picture quality can be dire, but if the sound is spot on then it will 'look' great. However beautifully shot footage with duff sound will seem awful.

The Richard Linklater film, Tape was also shot on on a camcorder. As was the very influential Timecode, the cameras for which were bought by the director Mike Figgis from consumer electronic shops on Tottenham Court Road in London.

Yes, Open Water.  I did not see it in a theater.  I believe the reason they chose the Sony PD150 was that was what they could afford.  The film was nearly all self-funded until near the end of production.  They were working and living their regular jobs/lives and taking weekend trips to make the movie.

BJL

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Do we have more pixels than we ever needed (in 4K video at least)?
« Reply #56 on: April 01, 2015, 05:58:31 pm »

Moving images look poor quality as screen grabs as they are deliberately shot at low shutter speeds to give a smooth image.
True, buy I was thinking about something different and simpler: you often see glaring pixelation in a frame grab, while pixelation is less noticeable or not at all noticeable when watching the video stream from which the frame was taken.  It is harder for our eyes and brains to make out fine details of a moving subject or image, probably in part for the reason I mentioned, about saccades.
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jjj

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Re: Do we have more pixels than we ever needed?
« Reply #57 on: April 02, 2015, 05:32:12 pm »

It is also worth remembering that 35mm movie projection in a good theatre has the resolution of only 600-800 horizontal lines, less than HD video.
Yet somehow manages to look so much better than that and why numbers do not always tel the truth - that's if those figures are even true.
I have a HD projector for watching at home and it produces an awesome 190cm/75" image. However it isn't a patch of films at the cinema which still look great at much closer effective viewing distances. If I was to sit close enough to my project's image to get the same field of view as I get at cinema, the image falls apart as I can see the pixels and information that makes up the image.
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