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markr041

10bit vs 8bit HDR (HLG) Shootout Video

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Is 8bit HDR or HLG a "joke"? Here is an HDR HLG video shot from the same camera (Sony FS5) using its internal 8bit 420 Slog2 XAVC and Slog2 recorded externally from 14bit RAW to 10bit ProRes HQ (Atomos Shogun). So the 8bit is heavily compressed (100 Mbps), the 10bit is not (950 Mbps!). Totally unfair to the 8bit. But, let's see...

Same scenes - for each the first version is from Slog2 ProRes 10bit, the second from XAVC 8bit SLog2 placed on the same timeline. The video was rendered in HLG 10bit DHxNR HQ in Resolve Studio and sent to YouTube. No color correction other than the Resolve presets converting Slog2 to HLG and level adjustments. It is a real HLG video. You can easily tell which is which, since the 10bit source from RAW is 4K DCI and the 8bit source is 4K UHD.

The video has plenty of blue sky, ripe for banding. And lots of detail, and high contrast with those pesky white clouds ripe for blowouts.

There is a difference. But does it matter? Is it fixable? A laughable joke?
 


If you do not like the test ("the test is a joke," "the test tells me nothing," "YouTube converts to 8bit anyway, so what?"), suggest what you would want to see instead. I can do anything with the original Slog2 clips, including making them available for download. 

Finally, why do we care about this? ALL Sony mirrorless cameras and camcorders less than $8,000 that have log gammas (Slog2/3) and/or HLG only shoot 4K in 8bit 420 - the RXxxx series, the A7xxx and the A6xxx series, and the FS5. If shooting in log or HLG at 8bit to make 4K HDR videos is a joke, that would call into question what Sony is trying to sell, and what anyone should consider buying (note, the GH5 can only do 10bit 422 in 4K30p, not 4K60p). No Canon cameras/camcorders do 4K 10bit below $8,000 either I think. And they have log gammas. Is this a big deal?

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EOSHD Pro Color for Sony cameras EOSHD Pro LOG for Sony CamerasEOSHD C-LOG and Film Profiles for All Canon DSLRs

Thanks so much, @markr041 . This was pretty much to be expected, as 10-bit has much more color information and doesn't break apart and become splotchy like we see in the 8-bit image. The 8-bit color looks washed out when compared to the 10-bit. These were shot in perfect lighting - but if you were shooting under more challenging conditions, or wanted to apply a moderate grade, it would conceivably be even much worse. Which is why every single authority without exception recommends 10-bit as the absolute minimum. I just don't understand how certain people here, who have never even uploaded a single HDR clip, can assert that just because Sony cheated on the specs, that they must have found a magic bullet. Just the same, for anyone who does own Sony, I'm guessing that delivering in 8-bit HDR will still have higher quality than SDR. 

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I think here you see the problems of both bitrate and bit depth with slog. The title is a bit confusing since this does not test the HLG directly. I would expect the differences between 8bit & 10bit HLG to be smaller. 

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The optimal test would be to record with a HLG instead of an SLOG with an external recorder at either 8 or 10bit. SLOG curves compress midtones more than HLG curves, whereas the opposite is true for the highlights. So shooting 8bit HLG should produce better results than shooting 8bit SLOG. The test with the SLOG should be the upper limit of any differences in the bit depth. Now how much visually it makes a difference for HDR delivery I couldn't tell since I don't have a HDR monitor :)  

 

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1 hour ago, Don Kotlos said:

The optimal test would be to record with a HLG instead of an SLOG with an external recorder at either 8 or 10bit. SLOG curves compress midtones more than HLG curves, whereas the opposite is true for the highlights. So shooting 8bit HLG should produce better results than shooting 8bit SLOG. The test with the SLOG should be the upper limit of any differences in the bit depth. Now how much visually it makes a difference for HDR delivery I couldn't tell since I don't have a HDR monitor :)  

 

I am guessing the difference in HLG may be much less. You either expose for the highlights OR the shadows. Also the colour isn't as flat as Log. It is therefore much closer to non-log profiles. 

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6 hours ago, markr041 said:

There is a difference. But does it matter?

On the long run, yes.

Your sky doesn't have a very steep gradient, and you don't move your camera. If you see Annihilation on Netflix (practically only watchable in HDR, for the SDR version lets all the highlights clip, unnecessarily) you'll notice a lot of lights with smooth gradients, and moving. 

Alistair Chapman provided a LUT for the FS7 (and others, the ones that support 10-bit and All-i, see below) to convert Slog3 to HLG, he calls it instant HDR. But he insists that Slog is actually preferable. My own experiences (but others confirm that) are, that Slog3 in 8-bit will make the above situations difficult. The other obstacle has nothing to do with bit depth but with compression. In Slog3, ETTR or not, you will often capture noise, and compressed noise ruins the image for good. Yes, yes, a field recorder. Do I want to use one when it doesn't give me 10-bit? No.

The 8-bit HLG-cameras are promoted by avoiding the difficult shots:

As far as I can see, there are very few highlights above IRE 100, the SDR version doesn't look dramatically different. Reflections on the waves, the medals on the shelf, sweat on the boxer's skin. I dare say that this clip wouldn't have looked better, or different, had it been in 10-bit ...

 

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This is a good discussion.

While you can shoot HLG internally in the FS5, you cannot externally shoot HLG directly using the Atomos Inferno from the FS5. Internally, the FS5 is set to Slog2, even for SDI RAW output. One has to convert Slog2 to something; could have been HDR10 or REC709. And, the differences one sees are due both to the bitrate difference and the large difference in the amount of compression.

All Sony cameras below $8,000 shoot in Slog2, 8bit. Sony has been touting this ability for many years. It's a feature allegedly designed for pros. So, if you want you can think of this test as a test of Sony's Slog2. But, again, Slog2 needs to be converted to a delivery format for viewing. And HLG is one of those.

One can record RAW video externally from the FS5 and then convert in software to REC709, HLG, or HDR10 using 8bit 420 and 10bit 422 and different amounts of compression for comparison. That would reveal what matters and by how much. But then such a comparison would have little do to do with what Sony cameras actually deliver internally, which is the point. One could also record HLG internally and compare that with HLG converted from the RAW output in post, choosing different bitrates and bit depth.

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@markr041 I finished a shoot this afternoon recording HLG with the GH5 to the Shogun Inferno, Prores HQ and when I imported the clips into Final Cut, they seemed to be rec.709. It’s been a long day, so rather than figure out what I did wrong, I went to a coffee shop to collect myself. It’s my first time using the Inferno. Anyhow, good thing the GH5 also records to the SD cards. One thing I will say is that you’ve got to be in much better shape than I’m in to handhold the Shogun all day long. Never again.

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20 minutes ago, jonpais said:

@markr041 I finished a shoot this afternoon recording HLG with the GH5 to the Shogun Inferno, Prores HQ and when I imported the clips into Final Cut, they seemed to be rec.709. It’s been a long day, so rather than figure out what I did wrong, I went to a coffee shop to collect myself. It’s my first time using the Inferno. Anyhow, good thing the GH5 also records to the SD cards. One thing I will say is that you’ve got to be in much better shape than I’m in to handhold the Shogun all day long. Never again.

We need  a non-screen, small and light recorder that has the same recording capability as the Shogun Inferno from Atomos. Now, I power the Inferno and the FS5 from one battery, using D-tap. That lightens the load considerably. But the size of the Shogun still makes it an awkward combo. My other technique is to to just put the Inferno in a shoulder bag, attached to the FS5 by the thin SDI cable. I really do not need the screen.

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29 minutes ago, jonpais said:

It’s my first time using the Inferno. Anyhow, good thing the GH5 also records to the SD cards. One thing I will say is that you’ve got to be in much better shape than I’m in to handhold the Shogun all day long. Never again.

Potential solution depending on how you're working....

Cage for the Shogun which you can then attach camera strap to. Cheap quick release plate on the cage to get it on and off your rig for when you want to monitor on it for composition setup etc and use the camera screen for actually shooting and have it over your shoulder when you don't. If you are mainly using it as a recorder then you can leave it over the shoulder and set the HDMI trigger to auto start stop when you press record on the GH5.

https://www.amazon.co.uk/SmallRig-Camera-Monitor-Assassin-Recorder-1788-Cage-1788/dp/B072MS5J3W

 

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Maybe somebody else also find as usefull as myself - I mostly replicated this one solution with Ninja Flame.... Also, I think that there's last update in Ninja Inferno and above recorders that support HLG from GH5.

 

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I think I've got the same issue as Mark: if you want to record to an external recorder for delivery in HDR, you've got to shoot V-log with Panasonic. Unless I'm doing something wrong...

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I see my Shogun is running firmware 8.4 and they're up to 8.42.

I'll give that a shot. v.8.42 includes the following bug fixes:

HDR HLG and PQ Loop out over value gain issue fixed.
Fixed an issue where the HDR slider value was not saved when using Auto HDR mode.

20% improvement to system start up time.

Their website says this:

SUBSEQUENT OS UPDATES EVERY 4-5 WEEKS WITH THE FOLLOWING FEATURE PRIORITY:

Raw Recording (Sony FS, Canon, Arri, Panasonic)
HLG In/Out
QuadLink
Scheduled Playlist

 

So I guess it's not just my imagination. :) 

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Also, I've made an compound lut which constists of HLG-to-Vlog + my own developed version of GHalexa for better rollofs + (sometimes) one of the Huan Melara's (although not original from himself) film print luts as (at least I've found so) best grading start point. And baked it in Atomos during recording.

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Hi guys am new to the GH5 and I am planning to use it underwater

HLG was one of the reasons to buy this camera as I have an HDR compatible tv however I have a problem with the camera as the display is not HDR and from what I see the same is true for Atomos Shogun the display is only REC709.

The camera has two HLG View assist options and I have not played with it to see what gives better results however I have also worked out that my iMac and almost no computer supports HLG

On final cut pro X I found that the option 'Show HDR as Raw values' in playback settings helps a lot and you need to revert to using REC709 and scopes or exposures to see what you are doing (this is to address jonpais post)

So my point is considering none of the external recorders nor the camera screen display is HLG how am I suppose to expose correctly? I have heard about setting zebra at 90% but it seems the camera can do more so I am thinking of moving to 95 % as with HLG you can't exceed or dropping the zebra altogether

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