Shooting HLG - First Experience

[Laval 21]

During my last trip to Raja Ampat I tried shooting HLG (Hybrid Log Gamma) with my new camcorder Sony HXR-NX80.

Before the trip I had no intention of shooting with HLG, but Juan Miguel Núñez Arellano (http://wetpixel.es) encouraged me to do so and mentored me during the trip providing me with valuable tips, and later - he guided me through post-processing of HLG footage.  I am very grateful to Juan for all his time and mentoring.  You could visit Juan's YouTube Channel to see his footage shut using HLG and recommended settings.

The following video is a collection of 4K underwater video clips shot in HDR HLG, BT2020 color space at various depths: 

https://youtu.be/JaL6gkwfJQY

The following equipment was used to make this video:

Camera: Sony camcorder  HXR-NX80

Housing: Gates AX700 / Z90 with Gates GP34A Wide Angle Port and internal UR Pro Red Filter

Video Lights: Keldan Video 8X 11,000 Lumen CRI 92 (5400K) with Keldan Ambient Filter M1 (10-20m) for 4X/8X

Camera Settings: 4K, 30 FPS, Picture Profile: BT2020.  I followed this ARTICLE for recommended camera settings.

All clips were converted to Rec.709 color space using the following two methods:
1 - FCPX HDR Tool 'HDR to Rec.709 SDR', and 
2 - Lemming Camera LUT 'Pro Sony A - HLG to Rec.709 and Custom LUT 'Quicker - Neutral Film'.

Please note that: 

• Clip #13 is a comparison between FCPX HDR Tool and RAW file.
• Clip #14 was shot using  SDR Rec.709.
• Clips #12, 13 and 14 were shot at the same point (Cape Kri site at 35 m) and at about the same time (at about 8:30 am), but clip #14 was shot a different day.

It is my understanding that the optimal depth range for the UR Pro Red Filter and Keldan Ambient Filter is between 10 and 20 m, and I found it to be a bit more challenging to grade footage shot outside of that depth range.  

In most cases, the difference between grading using the above two method is very minor, but I found that grading using Lemming Camera LUT gives a bit better result compared to FCPX HDR Tool (except of Clip #13), but it could be due to a lack of my experience.  Also, I should mention that I did not use much video lights as as specific situation demanded.

I will keep experimenting with HLG on my next trip.  Meanwhile, if you have any questions please let me know. In addition, I will appreciate your comments and constructive criticism.  I numbered all clips for the convenience of referencing to them. 

Best regards and thank you.

[PhotoJunkie 17]

Beautiful work, this is a technique that I was not aware of.  The results are very stunning.

[Interceptor121 843]

The Leeming LUT rebalances colors based on Xrite so this corrects the camera skew and once you white balance avoids you having to do it.

So it is not so much how the HLG to SDR is done but the LUT itself correcting the camera before the change

 

The link however is not working

[Lionfi2s 74]

Why are you shooting HLG and then convert it to REC709? Why not export as an HLG so people with HLG capable devices can enjoy HDR content, everyone else will still be able to watch it, as HLG is backwards compatible with SDR devices.

To be honest I didn't like the colors of the video (because this is what we are discussing about), colors are muddy, WB is off, you crashed the shadows in many areas that there where details to see (most probably the LUT does that). To be even more honest some clips are better in the ungraded version, especially the blue of the water. It reminded me issues I had when using  a Sony camera.

Also I think the UR pro is "too red" for the Keldan ambient filter and you would have better results if you skipped the filters altogether and just use the lights with a proper white balance method. 

HLG is not designed to be heavily graded, unless you are shooting really shallow and you wont do any color drastic color changes I cant find a reason to use it.

Sorry if it wasn't what you wanted to hear.  

 

[Interceptor121 843]

HLG specifications in ITU are 10 or 12 bits. I think 8 bits implementation look too coarse and are not useful

Sony has some a useful functionality to manage knee compression that works well for SDR content and this camcorder has a lot of settings for picture profile to play with

Going to HLG to come back to SDR is not something you do as HLG is backward compatible

In terms of grading HLG has to be good off the camera with no need for LUTs or grading at least this is what I do

[Lionfi2s 74]

The random shots on the link below are all HLG shots straight out of the camera, no adjustments in luminance or colour or white balance. Exported using a HLG workflow in Resolve.

They where shot in Egypt with a GH5/14-42 pz lens and WWL-1. Lights were some unbranded weak video lights that someone borrowed me since my checked luggage was misplaced by Egyptair. Dont know their lumen output or color temp. No filters used in camera or lights and no Luts.

 

[Interceptor121 843]

Nothing to call your mom about either

My general observation has always been that DR for underwater video is not a major consideration except for snorkelling even for stills unless you have a sunball right in the frame is not a concern

I have several doubts about HLG with 8 bits simple example an SDR signal goes from 0 to 100 nits and HDR 0 to 1000 so the signal is increased however the increased brightness is mapped by the same number of tones 256 which means there will be more distance between the tones and this will result in banding

The reason why HDR stipulates 10 or 12 bit depth is to avoid the banding. The Sony footage demonstrates that the standard has to be respected otherwise the footage looks coarse

Personally I even shoot SDR at 10 bits 422 and I see that it holds well even if I need to correct it extensively

Edited March 11, 2020 by Interceptor121

[davec13o2 7]

On 3/8/2020 at 3:39 PM, Laval said:

 Also, I should mention that I did not use much video lights as as specific situation demanded..

Looks good to me. 

Could you further explain your quoted comment above?  Do you mean you always used the lights, but at reduced intensity or did you not use lights at all in some situations?

Did you use a single light?  How long was the arm?

Would you say the level of your color grading was light, moderate, or heavy? 

What would be the reasons not to use HLG and BT2020?

Did you do any white balancing, or relied entirely on filters?

Have you projected these clips on an HDR TV?

Thanks for any comments,

Dave

Edited March 18, 2020 by davec13o2

[Laval 21]

On 3/18/2020 at 1:28 PM, davec13o2 said:

Looks good to me. 

Could you further explain your quoted comment above?  Do you mean you always used the lights, but at reduced intensity or did you not use lights at all in some situations?

Did you use a single light?  How long was the arm?

Would you say the level of your color grading was light, moderate, or heavy? 

What would be the reasons not to use HLG and BT2020?

Did you do any white balancing, or relied entirely on filters?

Have you projected these clips on an HDR TV?

Thanks for any comments,

Dave

Hi Dave,

Thank you for your comment ad interest.

Most of the times I did not use lights at all, as I thought that I was over-using them.  Also, I was experimenting with turning them downwards and even backwards, to avoid scaring fish.  Unfortunately, I do not have a good record of that to make any meaningful conclusions.

When I used lights, I used two of them. Each arm has two segments: 6 inch and 8 inch.

About 25% of all m y clips on the last trip I shot with HLG as an experiment, to see how I could grade them, even though I do not have an HDR monitor.  My thinking was that I would future-proof my footage: I could produce an Rec.709 video, but in the future, when I would have an HDR monitor, I could go back to these HLG clips and use them to produce HDR videos.

Also, it appears that it is not much more work to grade HLG footage by converting it to SLG Rec.709.

I always set WB for every shot.  It is very easy with this camera.

These clips looks much better on my HDR TV (Samsung).  I see much more depth in colors.

I hope I answered your questions.

You could read an article by Juan on wetpixel.es with his comments about my video:

https://wetpixel.es/valera-sakhnenko-filma-en-hdr-hlg-en-raja-ampat-y-utiliza-hdr-fcpx-hdr-a-rec-709-sdr-valera-sakhnenko-films-in-hdr-hlg-in-raja-ampat-and-use-hdr-fcpx-hdr-a-rec-709-sdr/

[Laval 21]

On 3/8/2020 at 8:39 PM, PhotoJunkie said:

Beautiful work, this is a technique that I was not aware of.  The results are very stunning.

Thank you, PhotoJunkie.  I appreciate your comments.

[Laval 21]

On 3/9/2020 at 6:31 AM, Interceptor121 said:

The Leeming LUT rebalances colors based on Xrite so this corrects the camera skew and once you white balance avoids you having to do it.

So it is not so much how the HLG to SDR is done but the LUT itself correcting the camera before the change

 

The link however is not working

Thank you for your comments.

Here is the link again: 

 

[Laval 21]

On 3/10/2020 at 2:54 AM, Lionfi2s said:

Why are you shooting HLG and then convert it to REC709? Why not export as an HLG so people with HLG capable devices can enjoy HDR content, everyone else will still be able to watch it, as HLG is backwards compatible with SDR devices.

To be honest I didn't like the colors of the video (because this is what we are discussing about), colors are muddy, WB is off, you crashed the shadows in many areas that there where details to see (most probably the LUT does that). To be even more honest some clips are better in the ungraded version, especially the blue of the water. It reminded me issues I had when using  a Sony camera.

Also I think the UR pro is "too red" for the Keldan ambient filter and you would have better results if you skipped the filters altogether and just use the lights with a proper white balance method. 

HLG is not designed to be heavily graded, unless you are shooting really shallow and you wont do any color drastic color changes I cant find a reason to use it.

Sorry if it wasn't what you wanted to hear.  

 

Thank you for your feedback, Lionfi2s.   I appreciate it.  I am still learning and experimenting, and honest feedback is always very helpful. 

[thani 86]

On 3/31/2020 at 4:23 PM, Laval said:

Thank you for your comments.

Here is the link again: 

 

Beautiful work. Thank you for sharing. Can you render the same clip in HDR so we can tell the difference?

 

[Laval 21]

I just posted a short video which Juan M. Núñez helped me to grade and export using Encoder Adobe Premiere MXF Intra 300 4.2.2.

I shot all footage used in this video, but because I do not have an HDR monitor, Juan M. Núñez, who has all right equipment, kindly agreed to grade a few of my clips and put this short video together, for which I am very grateful to him. 

You could visit Juan's website http://wetpixel.es to learn more about underwater videography in general  and about using HLG for underwater videography. Also, you could visit his YouTube channel at https://www.youtube.com/channel/UCnKjMMMzc7HFmFwSy40Nt4g

 

[Lionfi2s 74]

So these are HLG to SDR rec 709?

[Interceptor121 843]

Juan and I have different views about this.

Personally I do not advocate shooting HLG to convert to SDR. Firstly HLG already converts itself to SDR anyway as it is based on the same IRE system. Second HLG is hard to monitor without an HLG monitor and considering that metering is incorrect at best you are almost guaranteed to make the wrong decisions when you shoot on an SDR LCD

Finally HLG requires 10 bits to work, compressing the gamma curve over 8 bits means the digital scale is really rough and with insufficient grey levels this will generate banding and soft image. Both seems to be there in this clip.

I think 8 bits is for zero grade operations and the Sony camera is very ergonomic @Laval should use a rec709 profile with knee setting to protect the highlights perform white balance and aim at zero corrections in post. I would like to see an HLG version of this material unedited to see what it looks like.

I work with 10 bit files at much higher precision with a larger sensor and I would not shoot HLG underwater myself for those type of dive in Raja Ampat that tend to be pretty dark most times.

 

[davec13o2 7]

reconsidered

Edited April 4, 2020 by davec13o2
waiting to recompose

[Interceptor121 843]

5 hours ago, davec13o2 said:

So, with an 8 bit camera like the Sony a7Riii, you may as well shoot in xavcs at 1920x1080, Cine 2/Movie, for grading to taste on an sdr monitor and playback on an  sdr TV - to make the whole process straightforward?

Sony still cameras are notoriously inaccurate at colour rendition so am not sure how you get the baseline correct. It does not make sense shoot HD as sharpness is the only thing unaffected by compression or colour accuracy

[Laval 21]

On 4/3/2020 at 4:31 AM, Interceptor121 said:

Juan and I have different views about this.

Personally I do not advocate shooting HLG to convert to SDR. Firstly HLG already converts itself to SDR anyway as it is based on the same IRE system. Second HLG is hard to monitor without an HLG monitor and considering that metering is incorrect at best you are almost guaranteed to make the wrong decisions when you shoot on an SDR LCD

Finally HLG requires 10 bits to work, compressing the gamma curve over 8 bits means the digital scale is really rough and with insufficient grey levels this will generate banding and soft image. Both seems to be there in this clip.

I think 8 bits is for zero grade operations and the Sony camera is very ergonomic @Laval should use a rec709 profile with knee setting to protect the highlights perform white balance and aim at zero corrections in post. I would like to see an HLG version of this material unedited to see what it looks like.

I work with 10 bit files at much higher precision with a larger sensor and I would not shoot HLG underwater myself for those type of dive in Raja Ampat that tend to be pretty dark most times.

 

Thank you, Interceptor121.  I always like your posts.  They get me to research, think and experiment more.

[thani 86]

On 4/3/2020 at 12:31 PM, Interceptor121 said:

Juan and I have different views about this.

Personally I do not advocate shooting HLG to convert to SDR. Firstly HLG already converts itself to SDR anyway as it is based on the same IRE system. Second HLG is hard to monitor without an HLG monitor and considering that metering is incorrect at best you are almost guaranteed to make the wrong decisions when you shoot on an SDR LCD

Finally HLG requires 10 bits to work, compressing the gamma curve over 8 bits means the digital scale is really rough and with insufficient grey levels this will generate banding and soft image. Both seems to be there in this clip.

I think 8 bits is for zero grade operations and the Sony camera is very ergonomic @Laval should use a rec709 profile with knee setting to protect the highlights perform white balance and aim at zero corrections in post. I would like to see an HLG version of this material unedited to see what it looks like.

I work with 10 bit files at much higher precision with a larger sensor and I would not shoot HLG underwater myself for those type of dive in Raja Ampat that tend to be pretty dark most times.

 

I second this opinion. capture HLG/HDR export the HLG/HDR otherwise we are defeating the purpose by exporting to SDR, IMHO.

This is how google is advising for HDR for youtube:

https://support.google.com/youtube/answer/7126552?hl=en

“Upload High Dynamic Range (HDR) videos

You can upload High Dynamic Range (HDR) videos to YouTube. HDR videos show higher contrast with more colors than standard digital video.

Viewers can watch HDR videos on compatible mobile devices and HDR TVs. They can also stream HDR videos using Chromecast Ultra to an HDR TV. Viewers will see "HDR" after each quality option in the video player (for example, 1080p HDR).

Viewers watching on non-HDR devices will see the video as a standard dynamic range (SDR) video.”

Again, thank you for sharing.

 

[Laval 21]

On 3/11/2020 at 1:09 AM, Lionfi2s said:

The random shots on the link below are all HLG shots straight out of the camera, no adjustments in luminance or colour or white balance. Exported using a HLG workflow in Resolve.

They where shot in Egypt with a GH5/14-42 pz lens and WWL-1. Lights were some unbranded weak video lights that someone borrowed me since my checked luggage was misplaced by Egyptair. Dont know their lumen output or color temp. No filters used in camera or lights and no Luts.

 

I watched your video on my HDR TV, and, in my humble opinion, it shows good potential of using HLG underwater.  I appreciate that you do not have proper lights, but when there was sufficient light, I could see very rich, good colors.