Originally Posted by irkuck
You contradict yourself here: On one hand you rightly show that aliasing originates from bad work. Logically then the cure for aliasing is in correct work and not in 4K. You imply that 4K is panacea: if 2K is done badly then 4K can be done badly equally well.
Of course 4K can be done badly, it's already done all the time.
Difference is that there is a whole lot of 4K worklflow education being done, specially by RED, because RED cameras will only output RAW and people mess that up all the time and gives the camera a bad reputation.
Another part is the recently understood need for capturing in higher resolution than the intended output.
Red as an example; as the first 4K motion CMOS camera maker they started with a 4K sensor, but found soon out they needed higher resolution to downsampled in post, so they offered a sensor upgrade.
The best 2K camera Arri Alexa has a 2880x1620 CMOS sensor downsamples 1.5x in camera and outputs 2K ProRes files. It is not very sharp and does not fully resolve fine details so it is prone to artifacts if you are not very careful in post.
RED cameras has been the only 4K cameras till now, but Sony has now shifted their technology from their previous 2K CCD and releasing a 20MP CMOS camera that outputs 4K preprocessed in camera.
The Sony cameras 20MP sensor has double green photo-sites and the sensor is turned 45 degrees
so conventional CMOS pixelcount is about 15-17MP, just above the Red Epic-X camera.
When it comes to 35mm film; They are scanned for Digital Intermediate and edited digitally, for so to be printed back to film.
Up to recently this scan was done in 2K and is still done in 2K for those that don't have a budget for 4K scans.
But even those that can afford a 4K scan, which is best done in 6K and downsampled to 4K, just convert the 4K file to 2K ProRes, if the movie is not intended for 4K release.
They then edit, grade and color correct on the 2K file.
Best would be if they followed the 4K RAW type workflow which now quite recently been developed and Graded the finished edit on the full 4K scanned DI.
This is important to understand so one understands how they arrive at the results.
If we say that all movies shot on 35mm film and thereby the source is equal to each other, then all of them should look equally artifacts free on a DVD or BD.
But that is not a case.
Frequently movies are released that have sub-par image quality compare to other movies shot on 35mm.
Now you should start to understand the reasons for this.
Read this Arri Scan article, even if it is some years old, where they explain the quality difference between a 2K scan and a 4K scan.http://archiv.arri.de/news/newslette...al_systems.htm
The movie Gladiator was released on BD and nobody was very happy about the quality. Then in 2010 an new version was quietly released without any promotion about improved quality.
Only outer difference between the two releases was -2 at the end of the SKU number.
This new release was from a new 4K scan, regraded and authored.
Here are two downscaled for size crop examples showing the difference.(click on the thumbnail to see full size)
Here are more "mouseover" in full size. Find the # above the image to see all grabs.http://screenshotcomparison.com/comparison.php?id=76352http://screenshotcomparison.com/comparison.php?id=100http://screenshotcomparison.com/comp.../100/picture:3
In some images the difference isn't remarkable, but looking at the level of the resolved grain we can see how much better the new release is.
So the quality of the source is very important, and in HD the "sins" of mastering houses and studios is even more apparent than in SD/DVD.
Claim that clean 1080 source can come only from higher scans is not justified. It is more depending on the design of complete optical, electronic and digital processing system than just mere 4K. High-end professional equipment can provide clean 1080, low-end 4K will cut so many corners to get dirty 1080.
We of course have always assumed that high end equipment delivers clean 1080p, and to a certain degree from the newest scanners that is the case. (Arri Scanners now scans 3K for 2K delivery.)
But clean 1080p from digital cameras have not been possible in the past, due to sensor technology and the before mentioned shooting 2K for 2K.
The best and most used digital camera for movies has been the Sony F35, a 35mm equivalent size RGB CCD camera and the Panavision Genesis buildt on the F35.
The Sony F23 has also been used quite much, and is a 2/3" RGB CCD sensor, a camera based on the popular Sony 900F HD broadcast camera.
These are the High End cameras.
In addition we have all the other HD cameras, many of them with 4:3 aspect ratio sensors which are cropped for 16:9, which all gives less quality than the before mentioned cameras.
Here is a zone chart example of a Canon 7D DSLR video "lineskipping" CMOS, which in this case has to represent the "lower end" HD video cameras.
The F35 CCD 2K and a RED One-MX 4.5K which I believe here is windowed down to 2K.
Loook at the difference in resolving detail in the 100% crops. The 7D, even with 1920x1080 is just a "porridge mess". The F35 shows in finer details exactly the problems that end up as arifacts. The Red One is the only one that resolves clean.(click on it)
To conclude; there is always possible to "mess up" in all part of the chain in 4K too, and it will be done.
The positive is that the new and best 4K cameras will shoot at higher than 4K resolution for better 4K results and people starts to learn proper digital 4K workflow.
Another fact to understand; A motive in front of a 2K camera and a 4K or higer resolution camera is the same.
The 2K camera can not resolve the details, they will merge together in blocks or a "soupe" just because 2K is not enough resolution to represent the details. And details are very important part of good image quality.
Example also is sharpness: 2K has to be electronic sharpened more than 4K to appear sharp and this produces artifacts and can look "oversharpened", while a 4K camera will have a more natural sharpness. (ref. image in last link)
I just recently wrote two similar posts about this, mostly comparing RED cameras and Arri Alexa. The first one has another zone plate.http://www.avsforum.com/avs-vb/showp...0&postcount=67
The second one is more about workflow differences and some interesting links in the end about "The Girl with the Dragon Tattoo", the first movie that had a 4K DI workflow from start to end.http://www.avsforum.com/avs-vb/showp...8&postcount=85
And here is a framegrab from a Red Epic-X test; http://www.avsforum.com/avs-vb/showp...5&postcount=62