HDR vs compression question

[Gaston Fazio]

Hi all:

Im shooting 8K - 5:1 compression .... when I enable HDR, the compression jumps to 10:1.
Does that mean that my "A" track and "X"track will be at 10:1 ?

Any way to shot 8K HDR at 5:1??

Thanks in advance as always!!!

G

 

[Blair S. Paulsen]

AFAIK there's no way around the write speed cap and you are recording two discrete tracks...

Cheers - #19

 

[Alex.E]

Only if you reduce your resolution which may or may not work for you. The Recording Time tool from RED has a HDRX button you can enable.
https://www.red.com/recording-time

Edit: Just to clarify, you're specifically looking for HDRx and not HDR? I only ask because the title says HDR.

 

[Gaston Fazio]

Thanks guys!!!

Really appreciated

G.

 

[andrewhake]

Just to be clear you are talking bout HDRx right? Your camera is always shooting "HDR" when shooting raw, but yeah when shooting HDRx the compression ratio has to increase.

 

[Gaston Fazio]

Just to be clear you are talking bout HDRx right? Your camera is always shooting "HDR" when shooting raw, but yeah when shooting HDRx the compression ratio has to increase.

Yes Sr.

I forgot the "X"....

You can tell I was talking about HDRx when I mentioned the "A" and "X" track.

Thanks for the input

G

 

[Marc Wielage]

Shoot some tests. The Heliums have enough dynamic range, you may not need HDRx at all. Just shoot normally, follow the rules for key-to-fill ratio, and expose it reasonably well. The material holds up in post very well.

 

[Sabovic Adis]

+ 1000 on what Marc said!

 

[Phil Holland]

There's been a lot of discussion here regarding HDRx and "needing it" in camera anymore.

I agree, in most cases for general shooting considering the dynamic range of RED's latest sensors it's not the most needed thing.

However, where I've always found some goodness with HDRx is when filming timelapse. Very useful for day and night as well as transition filming.

That said, truthfully I don't use it much at all outside of that. It's still a nice and unique feature.

 

[Björn Benckert]

Yes HDRx is one of the greatest features of the reds I think. I don't care what DR the camera has this function gives more and it´s always good to have more... Of most things.

But also consider this. when doing 8k 10:1 you max out the bitrate flow. Same as 5:1 in single layer. If you use both layers I would say that you are not really compressing as hard as 10:1 two 10:1 mixed together can actually even be cleaner than one 5:1 layer. But sure if you do it without purpose and toss one track away in post then you wasted bandwidth.

Simply two differently compressed image of the same scene blended can actually be cleaner than one half compressed image of the same scene.

 

[Marc Wielage]

However, where I've always found some goodness with HDRx is when filming timelapse. Very useful for day and night as well as transition filming.

Special purposes like timelapse, sure.

 

[Gaston Fazio]

Hi Guys!

Just FYI... The client was shooting a sunrise here in Miami. Client was very specific about compression being 5:1.

Thanks all.

G

 

[Blair S. Paulsen]

FWIW, when testing HDRx, we discovered that careful grading of the A track yielded essentially the same results as mixing the tracks.

When HDR display tech reaches a legit 12 stops this side of $10K then perhaps the quest to hold 12+ stops in post will mean something. IMO, ATM, a good SDR display might show 9 stops, decent HDR monitors about 11 (most with color shifting above 80IRE) and some very expensive units from Dolby/Sony/Canon can do 12.

I hasten to add that unless your viewing environment is well controlled, the wetware will struggle to distinguish more than 10 stops anyway. Yes, in theory, humans with nominal vision can see 20 stops of DR - but only if several conditions are met. FWIW, once we get to 12 stops on the display side, there may be little value in pushing beyond that. On the acquisition side I'd love to go into grading with a 15 stop digital "neg". That said, if you nailed the exposure, I doubt you'd be unhappy with what you could get from 10 solid stops of DR at capture.

Short version - I'd advise less compression and live with the native DR.

Cheers - #19

 

[Björn Benckert]

FWIW, when testing HDRx, we discovered that careful grading of the A track yielded essentially the same results as mixing the tracks.

When HDR display tech reaches a legit 12 stops this side of $10K then perhaps the quest to hold 12+ stops in post will mean something. IMO, ATM, a good SDR display might show 9 stops, decent HDR monitors about 11 (most with color shifting above 80IRE) and some very expensive units from Dolby/Sony/Canon can do 12.

I hasten to add that unless your viewing environment is well controlled, the wetware will struggle to distinguish more than 10 stops anyway. Yes, in theory, humans with nominal vision can see 20 stops of DR - but only if several conditions are met. FWIW, once we get to 12 stops on the display side, there may be little value in pushing beyond that. On the acquisition side I'd love to go into grading with a 15 stop digital "neg". That said, if you nailed the exposure, I doubt you'd be unhappy with what you could get from 10 solid stops of DR at capture.

Short version - I'd advise less compression and live with the native DR.

Cheers - #19

Then you are doing it wrong.

The trick with HDRx is that your A track should be overexposed if the stoplights are not on for A track then sure you can grade it but then again the x track was absolutly no gain or need.

But if you open up so you are right at peak / stoplights flickering. Then set HDRx to 2 stops and open up yet another stop then you increased your DR by one stop and your X trax highlights will land 1 stop under peak.

If workimg it like that its possible to get way more out of an hdrx image than a single exposure.

and yes the above was just an example You can ofcourse go more extreme and do more than 2 stop Hdrx, then you motion blur will suffer more but your Latitude will increase even more.


When to use it?
When both goal posts are raised.

When using it the right way:
A track should burn and b track should have the left goalpost raised/pixels that does not sense light. Then its a question of motion in the scene to determain how much HDRX you can get away with.

 

[Marc Wielage]

FWIW, when testing HDRx, we discovered that careful grading of the A track yielded essentially the same results as mixing the tracks. Short version - I'd advise less compression and live with the native DR.

I agree 100% with Blair.

 

[Simon Dunne]

It's a nightmare to deal with in post and like others have said, a well exposed shot will get you what you need. Unless you're the NASA guys who hang around here and use HDRx to film shuttle launches. They expose for takeoff and have the X for the afterburners i think, so that they can check for malfunctions/debris during takeoff. It certainly does have its uses!

 

[Marc Wielage]

It's a nightmare to deal with in post and like others have said, a well exposed shot will get you what you need. Unless you're the NASA guys who hang around here and use HDRx to film shuttle launches. They expose for takeoff and have the X for the afterburners i think, so that they can check for malfunctions/debris during takeoff. It certainly does have its uses!

Yes, a massive exposure change (like 8 stops) for a rocket launch could well be one of those occasions. But a few actors talking in a room or walking outside? This is fixable with good lighting and good color correction.

 

[Blair S. Paulsen]

The truck that ran me over had HDR on the license plate...

The truck that ran me over had HDR on the license plate...

Keep in mind that by shooting 5:1, instead of 10:1, you're going to hold more fine detail (wavelet entropy codec characteristic). If you have more actual fine detail, then typical noise patterns are less prominent by comparison. This usually increases perceived S/N ratios, allowing you to extract more information from the shadows, which I contend extends useful DR by a full stop or more with many images.

It's very scene dependent, but from the HDRx tests I've been part of, 2 stops is about as far as you want to go before your risk of motion artifacting starts to get problematic. Then there's this; when comparing 1, 2 & 3 stops of HDRx vs single bracketed tracks (-1, 0, +1) on proper displays at a big color house, the problem wasn't a lack of discrete code values in any version. It was the natural limit to how many values you can shove into the graded image before it starts looking tone mapped and loses contrast snap. It was this experience that helped me understand both why HDR displays matter and how tricky it is to create offsets for SDR to HDR, or HDR to SDR, that retain the desired relationship between visual elements.

Tangent warning! (Colorist full employment program manifesto

One aspect of the HDR revolution I still struggle with is how to avoid changing important characteristics when creating HDR versions of content graded inside a 10 stop window. There's obvious ones like a distracting branch waving against the sky behind the primary subject that was blown out enough to barely register on a 10 stop master, but impossible to ignore in the 12-14 stop HDR version. An experienced colorist can manually tweak anything really annoying (or blur a sign that used to be lost in the sky, or deep in the shadows) by smoothly rolling off the top or crushing the toe - but will content owners/studios/distributors pay for a manual process? Or will we see some brutal AI fails when the wave of "remastered in HDR" library content starts blazing (pun intended) across our screens?

Perhaps more important to this community, is who gets to judge the HDR version's fidelity to original intent. In the US, most producers will not pay a DP to be in the color suite and may not even allow them to attend. In such a collaborative art, who is the "artist of record"? Typically the entity that funded production retains all rights, including creation of versions aimed at specific channels of distribution. Some filmmakers, Woody Allen for example, are able to secure durable creative control via contract provisions. That said, in far more cases, a title is resold or otherwise transferred to a party who had nothing to do with the creation of the work and can exploit it in virtually any manner they choose.

Full credit to the studios who have been willing to properly budget restorations/remastering/HDR versions that the director/DP/editor can feel pretty good about. A different palette is, well, different. That said, with proper understanding of original creative intent and an artist - not an algorithm - at the color board, most SDR content can benefit from being remapped to HDR. Just remember, all the DR in the world won't magically generate the right contrast characteristic and an automated SDR to HDR scale change tool can potentially ruin as many images as it improves.

Cheers - #19

 

[Blair S. Paulsen]

Yes, a massive exposure change (like 8 stops) for a rocket launch could well be one of those occasions. But a few actors talking in a room or walking outside? This is fixable with good lighting and good color correction.

Agreed. About the only time I still use HDRx, is for an interior shot up against a bright window that isn't going to get gelled (upper story, windy, no time, etc) where both the interior subjects and the exterior needs to read for a story beat, aesthetics, needs to cut with a low key scene, etc.

Cheers - #19

 

[Neil Abeynayake]

Hi Gaston,

Both Marc and Blair are giving you excellent advise here.

Your client might not be clear about how, why and when to use HDR in a project. Generally, we do NOT have to use HDR throughout the movie capture. You could use it selectively on most challenging scenes. If that person is asking for you to shoot 8k HDR @ 5:1 compression, he/she has no clue about RED's proprietary HDRX format. Show them or educate them about what they are getting out of it. Here is a link FYI:

https://www.red.com/red-101/hdrx-high-dynamic-range-video_3

I've had a few clients insisting things of this nature. I think most of these clients come from a DSLR background and they just whip cool sounding terms into their projects to show that they know more than you or their production is superior to the rest etc. So, I politely ask them where are they planning to showcase the end result. More often than not their answer is "Oh we want to add it to our latest ad on YouTube". Or, "It is going to be shown on our website and on our National TV ad campaign". That's the time I tell them what the reality is. 90% of TV sets are NOT HDR capable. Their dynamic range is around 8 to 10. Very few reference monitors and perhaps some OLED monitors might show somewhere between 10 to 14 stops of dynamic range. The RED camera already is over 16 stops of DR. If you expose properly, chances are you may not even need to do HDRX on camera. Maybe some scenes require or benefit by using HDRX. As discussed on a previous post, when someone is moving from an indoor scene to an outdoor one, I think a good focus puller with a FIZ system could do wonders that may bring in more of an organic look without going through too much pain.

In RED's tutorial you'd see a screenshot of a Metadata setting for a 5k WS HDR. It shows the compression set at 5:1. The camera is an Epic-M. But that is for 5k. Now if you were to change the camera resolution to 8k obviously the compression jumps to 10:1. The reason is, your camera has to deal with additional data overhead in comparison to a 5k data stream.

And if they still insist on this 5:1 compression @ 8k, ask them whether they have any "Other" camera platform in mind to do that process.