Por Que 4K?Is Higher Resolution Capture and Finishing Really Necessary?
(Excerpted from the Digital Cinema Society eNewsletter, October 2015)
by James Mathers
Cinematographer and Founder of the Digital Cinema Society
I’ve often been asked over the last few years, “Why 4K?” or in rhyming Spanish, “Por Que 4K? I’ve written about it before, but it is a constantly evolving equation which I believe merits a revisit. Acquiring in 4K and Finishing in 4K are two related, but different questions, so allow me to treat them as separate subjects.
It is definitely coming, but I’m not sure the need for 4K or higher resolution displays has really arrived yet, at least not in the home. The size of the display is a major limiting factor to the perception of resolution, and research tells us that a viewer would have to sit about 3 feet or closer from a 55-inch 4K TV to notice any real improvement over 1080p.
(See Carlton Bale’s oft quoted distance/screen size perception chart). What the chart shows is that for an 84-inch screen, 4K resolution isn’t fully apparent until you are at least 5.5 feet or closer. Even as home screens become larger and evermore affordable, most living rooms cannot physically accommodate much larger displays.
I should add, that true 4K content is still very limited. Netflix is a source of such 4K content, and I am a subscriber, but judging from the huge amount of compression they apply to HD, I’m not sure I would be satisfied with their 4K offerings. And I’m not about to see my $7.99 per month subscription jump 50% to $11.99 for the privilege.
All that being considered, if I were in need of a new TV today, I would buy a set that was capable of displaying 4K with a wide color gamut and also ready for HDR. To me, color and dynamic range are in many ways more impactful than resolution. As Dolby likes to say, improving picture quality is about using better pixels, not just more pixels.
Today’s content is often captured in a wide color gamut, but then mastered to fit the color space of HDTV, which is the Rec. 709 color space. Displays that can achieve the so called “2020” color gamut will show us colors that were never before achievable on electronic displays. In regard to contrast rations, most flat panels and projectors can currently only display pictures in the 1,000:1 to 2000:1 range, but HDR would give us something in the range of 5,000:1 or 10,000:1, a major increase in overall contrast.
Consumers want to buy electronics that are “future proof” — especially large ticket items like TVs that they may keep for a decade or more. So the trend will be toward higher quality displays in both the home and in theaters with screen sizes as large as the real estate will allow. So while HD may do the trick today, the smart producer, like the consumer, will also want to future proof their investment, which means mastering in 4K. If you’re delivering original content to such outlets as Netflix, Amazon, and several cable channels who demand 4K, then there is obviously no question about 4K.
I would add HDR and Wide Color Gamut to the recommended mastering order if it were not that the standards are still being debated. There are still various incompatible HDR methodologies competing for acceptance, and although the Rec 2020 standard is established, there are still issues to be addressed such as color accuracy, out-of-gamut mapping, and metameric variability. We have yet to even figure out how to properly measure variation in how individuals perceive these newly available colors.
The transition from HD to 4K reminds me of the one we experienced in the move from SD to HD, with one big exception. That difference is that we now have the benefit of experience, and can more easily avoid the pitfalls of this kind of change. If we don’t learn from our past mistakes we are doomed to repeat them, and in this case, the big mistake was when Producers would bury their heads in the sand and wait for the storm of change to blow over.
I remember shooting projects “at the turn of the century,” which sounds long ago and dramatic, but it was only a little over a decade ago. Some Producers were penny wise and pound foolish insisting we shoot Standard Definition to save a little bit on the front end, thus shooting themselves in the foot in terms of archival value.
In one documentary project, I literally circled the globe traveling to 16 different countries for a documentary on the world’s great religions. The B-roll alone would have been worth the price of admission, from the exotic Buddhist Temples in South East Asia to Whirling Dervishes in Turkey. However, the first airing on National Geographic happened to unfortunately coincide with the US invasion that started the Iraq War; needless to say, the ratings were not stellar. So, the program was lost in the shuffle, and by the time the rights reverted back to the Producers, some years later, the industry had transitioned to HD, greatly diminishing the program’s value.
For an incremental increase in upfront production costs, these Producers could have shot in HD, or even film, where they would be enjoying a healthy return on their investment today and into the future. I make the same case today, urging Producers to capture at the highest quality they can, and the smart ones listen. Owing to Moore’s Law and constant technological advances in Postproduction technology, finishing in 4K is getting to now be only incrementally more challenging than HD; so why not master in 4K?
Although I feel the main advantage of 4K at this point is archival value, there are a couple of creative opportunities worth mentioning. One is the ability to reframe as necessary in post, and the other is stabilization. If you shoot in 4K or above, and frame a little looser than your final intended frame, you can take advantage of that extra image area to achieve a bit of fudge factor for stabilization.
David Fincher, who has recently been acquiring in 6K for a 4K finish for such movies as Gone Girl is a big fan of this technique. He deliberately shoots with up-to-20% of the outer area of the captured frame considered from the get-go as a buffer zone with the assumption that it will likely be cropped out and is not part of picture.
Most projects don’t plan for stabilization or reframing, but despite our best efforts, a selected take (for performance reasons) may include a bump or awkward framing. When this happens the shot has to be stabilized and scaled. It can be nice to know that the resolution is there to support the scaling without losing apparent detail. And even if you’re only finishing in HD, down sampling always improves quality, so to my mind shooting at higher resolution is a no-brainer. The small challenges of handling a little extra data is well worth the effort.
Workflows, as is often quoted, are like snow flakes…each one is unique and they disappear as soon as they hit the ground. Re-inventing the wheel like this for each project is counter productive, but there are efforts currently afoot to help ease this situation.
The new Academy Color Encoding System, (ACES) is a great example. There are a lot of very smart people organized by the Science and Technology Council of the Academy of Motion Picture Arts and Sciences working very hard to implement an industry-wide system that will allow everyone to get on the same page technologically while still preserving creative color management choices.
From image capture through editing, VFX, mastering, public presentation, archiving and future remastering, ACES is designed to ensure a consistent color experience that preserves the filmmaker’s creative vision. It provides an image format and device independent processing parameters for each piece of the system throughout the pipeline.
4K, HDR, and Wider Color Gamut are separate matters, and I don’t mean to confuse the issue by combining them here, but each is a pillar in building the foundation for acquiring and delivering better looking images that will stand the test of time. You can find out more about 4K, ACES, HDR, Wide Color Gamut, and many other efforts to improve Post workflows at the upcoming Digital Cinema Society event, “4 Ways to a 4K Finish,” November 21st at Raleigh Studios in Hollywood.