In this lesson we’ll look at two things:
- General thoughts on the quality of 4K video from the Atomos Shogun
- Which Prores/DNxHR version to use for 4K?
General thoughts on the quality of 4K video from the Atomos Shogun
Here are the three versions of Prores (HQ, 422 and LT) from the Atomos Shogun (click to enlarge):
Please note, these tests are mostly irrelevant because I’m using Color Finesse, which behaves strangely with Prores footage from the Shogun. Don’t use them. Skip straight to the conclusions below.
Here are my general thoughts on UHD Prores HQ:
- You don’t have a choice if you’re recording 4K!
- S-Log2 in Prores/DNxHR works similarly to what you get in XAVC S.
- The resolution is definitely better, and you will get a better 1080p result if you start in 4K.
- There are only two things important when shooting 4K: Can you handle the data rates, and is your computer good enough to handle the workload (four times 1080p)?
Which Prores/DNxHR version to use for 4K?
If you study the above images, you’ll see:
- Visually, there is no difference between the three.
- However, Prores HQ really shows more ‘stuff’ (data). This means, you might want to use Prores HQ for any intensive grading, chroma keying, compositing or rendering work. For DNxHR, use HQX, because it’s 10-bit.
- For web-based work, Prores LT/DNxHD LB is more than adequate.
- For work that needs grading but does not need Prores HQ, you will do well with Prores 422 or LT, or DNxHD SQ or LB. You can ask yourself the same questions as in the last lesson.
How to choose between Prores LT and 422 (or DNxHR SQ vs LB) for grading?
It’s about data. Here’s something to read for starters.
In short, it is not by accident that broadcast standards demand a minimum of 50 Mbps for interframe compression, and 100 Mbps for intraframe compression, for 1080p. UHD has four times the data, which means, just to match the quality of a 100 Mbps intraframe 1080p stream (Prores is intraframe), you need 400 Mbps.
This is provided by Prores LT, just as it provides 100 Mbps for 1080p. The difference in data rates between 422 and LT are not sufficiently large, but you save 30% in disk space, and your hard drives and CPUs are stressed less.
The equivalent DNxHR codec that surpasses 400 Mbps is SQ.
Therefore, when in doubt, shoot Prores LT or DNxHR SQ. If you feel a particular scene might be difficult to grade, then shoot Prores HQ or DNxHR HQX.