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MLXXX

Does a 4K projector need "pixel perfect" resolution if the source material is a 4K animation?

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Yesterday, in the 2019 projectors releases thread, a brief comment was made to the effect that a native 4K projector was advantageous (over a 2K with-pixel-shift 4K projector) if the source was a 4K pc desktop, a 4K computer game, or a 4K animation, because these were "pixel perfect". The comment and my response to it have disappeared from that thread (apparently being considered too off-topic), so I am re-raising the issue here.

 

I think it's important to understand the limitations of even computer generated images when choosing a 4K pj. For the sake of simplicity in this discussion, I'm using 4K to refer to the UHD format 3840 x 2160 pixels.

 

1. A pc desktop

Lines and text on a pc desktop set  to 2160p will tend to result in hard boundaries at the pixel level. That effect can be reduced where the application generating the lines and text is feeding a resizeable window. This may involve use of anti-aliased text. See https://en.wikipedia.org/wiki/Font_rasterization

 

If using a spreadsheet full-screen on a 2160p desktop and choosing a very small font size for the cell content, a native 4K projector could indeed be an advantage as it could make the very small font legible when a 2K plus pixel shift pj might make some of the small font characters impossible to make out. (It would be necessary to view the pj screen from an unusually short distance.)

 

For general web surfing using a 2160p destop it should be possible to select a larger font size for text.  As for 4K video displayed using a 2160p computer desktop it will rarely if ever contain hard pixel boundaries. (This is to avoid aliases; see discussion below on animation as to why hard pixel boundaries are undesirable.)  

 

2. Pc gaming

In the past, games involving rapid movement were often played at 720p in preference to 1080p in order to achieve an acceptable game frame rate.  Even with expensive  graphics cards today it it can be challenging to achieve fast performance if the desktop is set to 2160p.

Because some parts of the game frame may be relatively static, e.g. game statistics, it is possible hard pixel boundaries will be generated by the gaming app. Also because anti-aliasing of movement in a game can use up precious processing resources, and because games typically don't aim for cinematic realism anyway, a game with fast movement may well generate non anti-aliased video, with hard pixel boundaries. In these circumstances a native 4K projector could provide a distinctly sharper look (if in fact the game is run at 2160p).

There are strategy games that don't involve fast movement. If such a game aims to create realistic, true to life looking video, it will need to avoid generating hard pixel boundaries. It would be counter-productive for the strategy game app to generate pixel perfect hard edges (unless it was intended that the frames would be subsequently rescaled or otherwise anti-aliased).

3. Animations

The closer a computer generated animation comes to looking realistic, the less likely it is to have hard pixel boundaries. It has become common for animations to be integrated into real life camera footage. For example in Avatar (2009) we could see human beings in the same scene as N'avi, the tall blue-skinned CGI generated inhabitants of Panadora.

 

Realistic looking animations are not "pixel perfect". Rather one pixel will bleed into the next. There are no hard boundaries between pixels. This applies whether the animation is hand drawn and photographed in the manner of a mid-20th century Walt Disney cartoon, or computer generated as in the 2018 movie, 
Jurassic World: Fallen Kingdom.

 

There should be little difference in appearance between a native 4K pj rendering a high quality 4K animation, and a 2K with pixel shift pj rendering the animation because animations are necessarily "soft" at pixel boundaries (to avoid looking artificial with moiré patterns or other aliasing artefacts).

 

So my suggested answer to the question posed in the thread topic is, "No".

 

The following comments made earlier this year on another forum by "Aaron Estrada, C.G. Supe. 20 years in VFX & Animation. DWA, R&H, Imageworks" are relevant. From  https://www.quora.com/What-resolution-is-CGI-for-movies-usually-rendered-at :-

 



Before the advent of Digital Cinema most film scan and film VFX were done at “2k” resolution. The exact raster of “2k” depended on the particular film format and aspect ratio. (Anamorphic 2.35, flat 1.85, or whatever) It was never perfectly standardized so various shops would sometime use slightly different numbers. Typically it was somewhere in the window of 2048x1556 (which would be what a “full app” scan of four perf silent 35mm would be) Often the actual working resolution would be smaller than that since the post house doing the scanning would keep the scanner calibrated for full-app and just extract the section of the scan you were interested in. Or they would just scan it full-app and provide the whole image. It really just depended on the particular workflow in use.

 

Now that nearly everything is shot on digital, the working resolution for CG and VFX will usually be the resolution of the target Digital Cinema Package format the film is meant to be delivered in. So, anywhere from 1998 × 1080 to 4096 × 2160, depending on the intended display aspect ratio.

 

In almost no case will the work ever be done at a HIGHER resolution than the intended exhibition format, except for very special occasions when there is a good technical reason for it. For example, in the case of the Queen of Hearts in Alice, the places for the queen were shot at 4k to accommodate the manipulations for making her head look bigger without stretching the pixels larger than they would be in the final output images. (the film was delivered at 2k)

 

For cartoon style full CG animation, the output resolution is sometimes rendered at a LOWER resolution than the intended output target. This is because CG tends to be too sharp looking anyway, and the render times for a given image are heavily dependent on the number of pixels that need to be rendered. Rendering at a lower resolution allows the render time saved by rendering at a lower res to be applied to other features where it is more valuable, like improved motion blur and antialiasing. Better motion blur and antialiasing make the rendered image look more natural and are often considered a better trade off than a poorer anti-aliased, higher resolution representation.

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For data and big room presentation I believe it needs to be, particularly if the source benefits from having the greater resolution.  For example, when new movies, games, technologies or magnification of detailed scenarios like medical research come out requiring the demonstration of improved picture quality then you certainly need the right tools to do that.  For actual desktop usage I can't see how projectors can be a viable option for desktop users or gamers for prolong use (neck strains and whathaveyou).  For graphic and developers, they would prefer something where they don't have to put up with jaggies.

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from slightly different perspective...

PPI density combined with viewing distance and software algorithm (smoothing) where dark pixel gradually becomes light pixel (what you might be calling hard edges?)

simple math for this purpose, perceived visual effect of PPI density when you looking at 100" 8Mp (UHD) screen from 3 meters distance should be the same as 50" 4Mp (2K) screen from 1.5 meters or opposite 50" screen watched from 3 meters should appear the same as 100" from 6 meters (give or take, there should be exact formula somewhere on the net) 

There is plenty of info on the net about human's eye ability to capture pixel per inch density vs. distance and screen size but we are nowhere near that figure at the moment (in terms of projecting HW) so anything less than equal of humans eye ability will lead to visual side effects

additional conditions comes to play, quality of projecting unit (PJ/TV/Monitor) , lightning condition in the room and of course source (movie) quality (4K master, remaster, upscaled etc.)

 

On ‎14‎/‎09‎/‎2018 at 12:19 PM, MLXXX said:

The closer a computer generated animation comes to looking realistic, the less likely it is to have hard pixel boundaries. It has become common for animations to be integrated into real life camera footage. For example in Avatar (2009) we could see human beings in the same scene as N'avi, the tall blue-skinned CGI generated inhabitants of Panadora.

 

Realistic looking animations are not "pixel perfect". Rather one pixel will bleed into the next. There are no hard boundaries between pixels. 

in my view yes and no, from simple pixel perspective the picture will be pixel perfect, but as stated in your quote from Aaron Estrada, producer might consider different techniques so that the image looks as realistic as possible on every screen in every resolution and doesn't require additional hours of processing and HW, secondly there's no perfect recording or visual device so producers have to overcome side effects such as moiré, aliasing, posterization etc, now we also have to consider that 4K isn't native/standard resolution these days (yet) for home usage so if they have to please all of us than they have to find the middle road.

But there's no reason 4K master even if CGI generated can't look good if (again) mastering, final screen size and watching distance stays within intended boundaries

 

so the answer is yes if above mentioned would be achieved... 

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This topic was posted in response to my comments in another thread. This is silly. I have actually looked at this in the real world.

 

It is folly to state a pixel shifting 3k image is fine when the source image is in fact 4k input resolution, forget the content MTF, think about 1:1 pixel mapping. It is ridiculous fundamentally to display 4k pixels at 3k. There is simple degradation there, end of story.

 

As for weather eshift can display all the MTF that is there in 4K UHD films. It simply CANNOT. End of story. I have seen it with my own eyes.
 

Here:

 

4K Lucy. Look at the fibres in his suit on the right at 100%, zoom in, do whatever you need to do. This information is NOT there in the 2K image.

 

yABpYUJ.jpg

 

2K Image

 

tNuVQme.png

 

Here is MadVR NGU Sharp up-scaling to 4K. Better but the detail is still not there.

 

ttKxaUG.jpg

 

Even the very best up-scaling does not restore this information.

 

Now you might say that the 4k image on an eshift machine renders the detail just fine if you use the UHD source (I thought everyone on here thinks UHD is BS?), well, sorry, I have looked at this with eshift 4 and eshift 5, it does not render the fibres still. Add to that, there is moire on the very fine fibers in his suit going in the wrong direction, and the detail is completely blurred away. 4K resolution displays the fibers exactly as they are present in the source. The fact is, the detail present in this frame at anything lower than a 4k native display cannot be rendered faithfully. This is not even animation!

 

Here is how the X9500 renders the UHD shot. Almost there, but a lot of detail is truncated. I dont have the 9900 shot handy, but its the same deal,. those extra fine fibers are missing or severely truncated.

 

c6STQW8.jpg

 

Case closed, sorry guys.

 

If you want to present me with actual source frames and real world experience to the contrary above, I am all ears. All I am reading is postulation and theory and no experience.

Edited by Javs

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6 hours ago, Javs said:

Case closed, sorry guys.

 

If you want to present me with actual source frames and real world experience to the contrary above, I am all ears.

 

I have had difficulty photographing UHD images that appear on a flat panel TV screen. What I've seen with my eyes has not always revealed by the camera. One way towards overcoming that is to set up the camera so that it captures only a portion of the screen, and then downscale the captured image of that portion. That technique may not overcome colour balance issues (because camera sensors will typically not have the same spectral response as the subpixel colours emitted by the display device) but may facilitate visible resolution being evaluated subjectively.

 

Javs, I can see that the original 4K frame (a rip from a disc?) has much richer colour overall, and much better detail for the pattern in the suit coat, than the screen photograph of the faux 4K projector.
 

Would you have a good quality screen photograph of what a native 4K projector does with that particular frame so we could see a real world A and B comparison?  Ideally two projectors under comparison would have been set up side by side and the same camera would have been used to capture the projector screen images.

[I have some remarks to make regarding visible resolution typically found on Blu-ray discs but will leave that till I have more time to post.] 

Edited by MLXXX

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Javs is spot on.  Just  take a look and you can easily see the differences. No need to theorise because the argument can be settled in the real world.

 

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41 minutes ago, MLXXX said:

 

I have had difficulty photographing UHD images that appear on a flat panel TV screen. What I've seen with my eyes has not always revealed by the camera. One way towards overcoming that is to set up the camera so that it captures only a portion of the screen, and then downscale the captured image of that portion. That technique may not overcome colour balance issues (because camera sensors will typically not have the same spectral response as the subpixel colours emitted by the display device) but may facilitate visible resolution being evaluated subjectively.

 

Javs, I can see that the original 4K frame (a rip from a disc?) has much richer colour overall, and much better detail for the pattern in the suit coat, than the screen photograph of the faux 4K projector.
 

Would you have a good quality screen photograph of what native 4K projector does with that particular frame so we could see a real world A and B comparison?  Ideally two projectors under comparison would have been set up side by side and the same camera would have been used to capture the projector screen images.

[I have some remarks to make regarding visible resolution typically found on Blu-ray discs but will leave that till I have more time to post.] 

Please ignore colours. We are focusing on a grey suit right now anyway, the HDR image is tone mapping to Rec709 so its completely not the colour you see in projection at P3.

 

I want to stress before I post this, comparisons as you say need to be photographed in person at the same time. But, I do have a pretty good camera, Canon 7D Mark II and good lenses. When my images are in focus, (the ones I posted are) the resulting image is very close to what I see in person.

 

So in saying that, here is the 760ES with the same shot. I cannot get close to this image on my JVC's and I have looked at this shot on 4 different JVC's so I am very familiar with it. The 760 (colour aside obviously) is closer to the source in this shot (in terms of actual resolution visible) than the JVC hands down.

 

760ES:

 

WfJG8VF.jpg

Edited by Javs

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57 minutes ago, Javs said:

Please ignore colours. We are focusing on a grey suit right now anyway, the HDR image is tone mapping to Rec709 so its completely not the colour you see in projection at P3.

 

I want to stress before I post this, comparisons as you say need to be photographed in person at the same time. But, I do have a pretty good camera, Canon 7D Mark II and good lenses. When my images are in focus, (the ones I posted are) the resulting image is very close to what I see in person.

 

So in saying that, here is the 760ES with the same shot. I cannot get close to this image on my JVC's and I have looked at this shot on 4 different JVC's so I am very familiar with it. The 760 (colour aside obviously) is closer to the source in this shot (in terms of actual resolution visible) than the JVC hands down.

 

760ES:

 

WfJG8VF.jpg

I actually see a lot more detail and texture in the guys face in the jvc shot ?. this one lookslots more pasty detail smoothened over ?  like its out of focus ? different camera ? different lens ? different distance. i find in taking shots always good to take from viewing distance and using 50mm equivalent as it best approximates what human eye can see :)

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2 hours ago, Javs said:

 

Case closed, sorry guys.

 

If you want to present me with actual source frames and real world experience to the contrary above, I am all ears. All I am reading is postulation and theory and no experience.

Who are you?  There's no need to get all high and almighty posting a few photos to prove your point, I think we all know 2K isn't going to be 4K and upscaling isn't going to make it better either.

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18 minutes ago, :) al said:

I actually see a lot more detail and texture in the guys face in the jvc shot ?. this one lookslots more pasty detail smoothened over ?  like its out of focus ? different camera ? different lens ? different distance. i find in taking shots always good to take from viewing distance and using 50mm equivalent as it best approximates what human eye can see :)

Look at his suit bottom right.... The 760ES obviously needs to be calibrated since it was not at the time. But calibration does not change resolution. There are details in his suit the JVC didnt resolve, simple as that.

 

28mm from 1.6 crop camera same thing... ~44mm full frame. I take them from about 3.2m.

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