A7III 4K Downsample to 1080p

David Del Real

David Del Real

Well-known member
I posted this over at EOSHD too:

Okay, so not to derail the thread, but on my A7III when downsampling in post from 4K to 1080p, the image looks terrible. Soft and aliasing. When I had the GH4 the downsampling was great. It retained details very well.

I've tried SLog2 and HLG3 but right now using Cine4 - getting the same soft result for all profiles (when downsampling in post). I do have Detail set to -6 but I think that shouldn't matter.

What gives? Am I doing something wrong?

Oh, and I've tried in FCPX, Premiere Pro, and Resolve. Premiere Pro seemed to give the best results out of the three but I had to use Unsharp Make at 50 and Sharpen at 20. Just doesn't seem right. Any help or suggestions would be greatly appreciated.



The 4K is amazing. I mostly shoot and deliver in 4K but there are times I want to shoot 120FPS. I'm a bigger fan of downscaling than upscaling so I thought that shooting 4K and downsampling to 1080 to match the 1080 120FPS would be the route to go. I'm thinking now that maybe I should just try to get away with shooting slo mo as 4K 30 with 120 Shutter and slow in post as much as possible without making the footage choppy... if only it had 4K 60...
 
That's been a common question over the years and many people are surprised when they experience this.

The simple and short answer is the camera is crippled by a corporate decision to not provide high-quality oversampling for its lower-resolution modes (especially HFRs; 120p, 240p).

99% of of 4K consumer/prosumer cameras do this, and the higher resolution modes for all of them are always much, much better.

For those cameras that are affected, the only workaround is to feed the 4K signal into a HD-only recorder (such as the BM Video Assist) to capture high-quality 1080p.

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P.S. I started shooting 4K in 2014 with a Blackmagic and after I sold it I "suffered" for the next 4 years mixing 1080/60p footage with the high-quality 4K material and it was just never the same. I tried 40 different 1080p cameras to no avail, and also shot at 4K/30p with a higher shutter, but a lot of scenes just didn't work because of either the choppy motion or the 'warping' when edges met.

[For this reason alone, the GH5/GH5s are on my list as two of the best cameras ever made because of Panasonic offering 4K/60p in a small and inexpensive package.]

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P.P.S. I was very disappointed in Sony last year for not releasing a mirrorless with 4K/60p.
 
I also wanted to add before (but was sidetracked) that I may have misread a bit and if you're talking about only post-production downsampling and not being satisfied with the results then I think it's just your settings: 120p is much softer than the 4K, and the low detail value does matter. (Pump it up a bit and you should notice a difference.)

Personally, I also dislike 4K on a 1080p timeline because of all of the information that's lost.
 
NorBro said:
I also wanted to add before (but was sidetracked) that I may have misread a bit and if you're talking about only post-production downsampling and not being satisfied with the results then I think it's just your settings: 120p is much softer than the 4K, and the low detail value does matter. (Pump it up a bit and you should notice a difference.)

Personally, I also dislike 4K on a 1080p timeline because of all of the information that's lost.
Click to expand...

I just tried with the Detail set to 0. Still weird, nothing like what I saw on the GH4. Odd. Seems like the downsampling would be much better than this. Also, yes, the 1080p is much softer when recorded that way but I'm talking about 4K downsampled to 1080p in post. Sucks that the 1080p in camera is bad too (well, relative anyway).

jcs said:
Can you put a short sample clip straight from the camera online, e.g. google drive?
Click to expand...

On a shoot with NDA. I'll try some test shots to post later.
 
Update:

So retried in Resolve. I noticed my settings were incorrect on the first try, so I adjusted my input and output scaling and set zoom to .500 and bingo, it worked much better. The downsampling algorithm must be really good in Resolve. FCPX and Premiere Pro still look wonky (must be a Quicktime thing) but if it works in Resolve, I'm okay - and yes, I used Spatial Conform to "None" and set to 50% scale in FCPX and in Premiere Pro I right clicked the clip in the timeline and selected "Set To Frame Size." Again, same lame results in those two NLE's. Davinci Resolve it is then. Thanks for your input guys, really appreciate it.
 
In FCPX, maybe next time try "Fit" or "Fill" and zoom in instead and see if that matters.

I've worked with 4K footage in FCPX on 1080p timelines for years and never noticed anything out of the ordinary besides less detail (naturally).
 
Both cameras definitely provide the same results when comparing them to each other.

In standard framerates (24p, 30p and 60p), they arguably - and I say that because it's a question of will anyone actually notice? - provide better results than their predecessors (a7RII & a7SII).

With HFRs, it's 100% noticeable. And this is where you can really sit down and evaluate the technological progression.

The a7RII only has 720/120p and it's garbage. The a7SII's and then the a6300's 120p improved a little bit. Fast forward 4-5 years later and the 1080/120p from the a7III and a7RIII is much better. And it's not even about the slight increase in resolution but more about less noise, less aliasing, less pixel-binning, and better color information from the improved technology.

For whatever reason, a lot of these companies are choosing to hinder the full potential of the lower resolutions, especially Canon who is notorious for this besides with the 1DC (although I hear the new EOS R may have finally changed that).
 
P.S. For the sake of sharing more information (learning is always good), here's a write-up that compares the 4K from the a7III and a7RIII.

In my personal opinion, no human would be able to tell the difference in this particular case, however, when comparing cameras from different generations, definitely.

"The A7 III takes advantage of the full width of the sensor to perform full pixel readout without pixel binning, gathering the equivalent of 6K resolution that is then down-sampled to 4K. This works at 24 and 25fps, while at 30fps the camera crops the sensor by 1.2x, gathering 5K of resolution instead.

Because it has more megapixels, the A7r III gives you the best results in APS-C/Super35 mode, where it gathers 5K of data that is then downscaled to 4K. You can record 4K in full frame mode as well but the quality decreases, especially at high ISOs where there is more visible noise."

https://mirrorlesscomparison.com/preview/sony-a7iii-vs-a7riii/
 
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