GH5 Paul Leemings New LUT for HLG Footage

visceralpsyche said:
Vesku, the footage from the camera in HLG needs to be converted to work properly on Rec709 displays...
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Paul, that's not correct. An HLG signal displays just fine on a SDR display. In fact, backward compatibility without metadata is its reason to exist.

More accurate to say that if you want to map the extended HDR luminance into an SDR range with a different, more pleasing curve, you can use a LUT like yours.
 
joe12south said:
Paul, that's not correct. An HLG signal displays just fine on a SDR display.
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Actually, that's not correct either. Some of the HLG luminance range does not display correctly on SDR displays, where it looks great on HDR displays.

Here's an example. Take a look at Nick Driftwood's short "Isobel" that he shot with the GH5 in HLG mode. At 0:51 there is a scene of white cliffs in sunlight that is obviously clipping when viewed on a SDR display, but it does not clip when viewed with a HDR display. Most of "Isobel" is very viewable on a SDR display, but some parts like the white cliffs do not display correctly.

 
TheDingo said:
Actually, that's not correct either. Some of the HLG luminance range does not display correctly on SDR displays, where it looks great on HDR displays.

Here's an example. Take a look at Nick Driftwood's short "Isobel" that he shot with the GH5 in HLG mode. At 0:51 there is a scene of white cliffs in sunlight that is obviously clipping when viewed on a SDR display, but it does not clip when viewed with a HDR display. Most of "Isobel" is very viewable on a SDR display, but some parts like the white cliffs do not display correctly.

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No, sorry, not to be pedantic, but what I said is correct. The behavior you note is *exactly* what is expected on a SDR display. It *is* displaying correctly. The midlevels (the bulk of the PI) remain basically where expected (generally slightly darker than the typical REC709 master) and the luminance information extends outside the legal range. (Effectively "super-whites.")

Like I said, if you don't like the standard curve, and you are ONLY mastering for SDR, you are free to design a different curve. That's what Paul's LUT does. If you want a picture that works for both, then you should master for HDR and deliver as HLG.
 
joe12south said:
The behavior you note is *exactly* what is expected on a SDR display. It *is* displaying correctly.
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I would not consider clipped highlights to be "displaying correctly" or "An HLG signal displays just fine on a SDR display."

To me it's an obvious SDR limitation when viewing HGL footage, and we have to live with this defect until SDR displays become a thing of the past.
 
TheDingo said:
I would not consider clipped highlights to be "displaying correctly" or "An HLG signal displays just fine on a SDR display."

To me it's an obvious SDR limitation when viewing HGL footage, and we have to live with this defect until SDR displays become a thing of the past.
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"Defect" is a poor choice of language that doesn't help people understand the purpose of the HLG standard. HLG was very specifically designed by some very smart people to be a very good compromise between SDR and HDR equipment, bridging the generation gap in what is, quite frankly, a pretty elegant solution. The clipping is 100% intentional, 100% expected and by no definition of the word a "defect." As you said, it is a "limitation" of backwards compatibility with legacy displays.

If YouTube *wanted* to, they could actually create a different "intent" and apply a different curve to the display of HDR material on an SDR display to compress that extra information. But representing the signal as an HLG curve ensures that they don't *have* to. Remember, broadcasters don't have that luxury.
 
When I watch GH5 HLG clips with SDR settings the image is dull and has low saturation. The highlights dont clip. Highs and mids looks much darker than in normal profiles. The whole image is dark and dim. Only the black are the same. If I use TV max brightness and contrast and added saturation the HLG looks good in SDR TV. A LUT or curve is needed for normal looking image for rec709 display. The theory is nice but the practise is different.
 
Yup, that example is what I would expect without there being any "intent" behind either the acquisition or the display.
 
joe12south said:
Yup, that example is what I would expect without there being any "intent" behind either the acquisition or the display.
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Too dark and unwatchable in SDR display without adjustments. I dont see that automatic HL clipping you mentioned before.
 
Vesku said:
Too dark and unwatchable in SDR display without adjustments. I dont see that automatic HL clipping you mentioned before.
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One man's "unwatchable" is another man's "fine". Not only do opinions differ, but different displays will handle this differently, including some devices that know that they are receiving a HLG signal, are connected to an SDR display, and adjust their "intent" to use a curve you would find more pleasing (YouTube, Apple TV, etc.)

If you want to optimize for SDR, then you should master for SDR. If you want to optimize for HDR, then you should master for HDR10 or Dolby Vision. If you need to support both in one deliverable, the HLG is the best (only) choice.
 
joe12south said:
...different displays will handle this differently, including some devices that know that they are receiving a HLG signal...
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I wonder why HLG is not using "superwhites" for added HL dynamic range. The file would clip automatically with SDR display but the superwhites could be seen with HLG standard. Now GH5 HLG records limited range 64-940 levels. The levels 941-1024 could store more highlights but that added HL data would not affect SDR image to bee too muted.
 
Vesku said:
I wonder why HLG is not using "superwhites" for added HL dynamic range. The file would clip automatically with SDR display but the superwhites could be seen with HLG standard. Now GH5 HLG records limited range 64-940 levels. The levels 941-1024 could store more highlights but that added HL data would not affect SDR image to bee too muted.
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Good question. Unlike V-Log, there's no backward compatibility issue with Panasonic's pro cameras, so why cripple HLG encoding range on the GH5? Panasonic seems intent on imposing "consumer" limitations on the GH line.
 
Lpowell said:
Good question. Unlike V-Log, there's no backward compatibility issue with Panasonic's pro cameras, so why cripple HLG encoding range on the GH5? Panasonic seems intent on imposing "consumer" limitations on the GH line.
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I think HLG is an universal standard so Panasonic can not make own versions of it. I think it is the historical burden of 16-235 in screens, TVs, editors and players which made the industry to choose limited range for HLG standard. If Sony will use 8bit HLG with coming cameras this will be a limiting factor for IQ smoothness.

Edit: Limited luminance scale is part of rec2020 standard and HLG uses rec2020.

HLG is very very good and has less noise than normal profiles. It just does not look good in SDR settings like the theory claims.
 
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I’d really be interested in knowing whether it’s the operator, who spends every waking moment of every day nitpicking and finding fault - is it the pixel peeper or the camera that is crippled? Because the very idea of Panasonic’s GH5, which has everything thrown in but the kitchen sink being crippled is absolutely ludicrous.
 
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Vesku said:
I think HLG is an universal standard so Panasonic can not make own versions of it. I think it is the historical burden of 16-235 in screens, TVs, editors and players which made the industry to choose limited range for HLG standard. If Sony will use 8bit HLG with coming cameras this will be a limiting factor for IQ smoothness.

Edit: Limited luminance scale is part of rec2020 standard and HLG uses rec2020.

HLG is very very good and has less noise than normal profiles. It just does not look good in SDR settings like the theory claims.
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The word hybrid is in there for a very good reason. Hybrid solutions are rarely perfect but offer a compromise to solve a problem in a decent way. Hybrid Log Gamma does what it does very well but I think expecting it to have 100% perfect SDR and 100% HDR all within the same space is just a tiny bit unrealistic. It is designed to provide decent results for both systems with the key word being decent. HLG is also a consumer standard and therefore only really designed to provide decent consumer experiences with the emphasis on supporting the future of more people eventually using HDR displays and SDR going bye bye.

Moving to new TV technology will always leave the older formats not as optimized as we would like. 4x3 interlaced SD video still kind of looks better on a tube based TV based on how it works wit that kind of video. The only time in history the move didn't hurt the previous standard was the move from black and white to color in the NTSC world.

The reality of shooting HLG is that the distribution intent is in fact HLG and therefore it will be more optimized to work better on a HLG display. SDR is sort of in there for the ride and to throw a bone to the SDR folks until the industry catches up. Eventually HLG will be completely pointless since there will no longer be a need to support SDR. Its a stop gap and filler solution until HDR becomes the common norm.
 
Well put, Thomas.

I think the frustration that many are feeling is because Panasonic doesn't give its users a profile that is not artificially limited in some way. VLOG-L is compromised in order to be compatible with V-LOG. HLG is compromised for the aforementioned reasons.

There's no technical reason the GH5 can't offer a profile that utilizes all available signal bandwidth to represent all the dynamic range that the image pipeline is capable of resolving. It takes no more hardware, no more processing, no more speed, no more anything...just simply the desire to do so. Sony's SLOG flavors demonstrate how
 
joe12south said:
There's no technical reason the GH5 can't offer a profile that utilizes all available signal bandwidth to represent all the dynamic range that the image pipeline is capable of resolving. It takes no more hardware, no more processing, no more speed, no more anything...just simply the desire to do so. Sony's SLOG flavors demonstrate how
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A 8 bit 0-255 profile (HLG like) with all the sensor dynamic range would be nice to have. It would allow HDR 4k 60P without using Vlog-L. Sony has already 8bit HLG profile in AX700 but I think it is 16-235.
 
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