Rec 2020 turns Reds Black? Any fix?
JasonWNalley
Posts: 122
Haven't tried to fully render it as a video yet, but in the Iray preview, all of the red surfaces have turned black when using Rec 2020. I'd *like* to render out a full Rec 2020 colorspace so I can grade for HDR if that's possible with DAZ, but this issue is throwing me off a bit. Any ideas?
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Is your monitor callibrated?
It all looks a little less red with the latest beta. Still not that nice. Sometimes it helps to set down saturation to around 70%.
Ok, after a bit of experimentation, I think I have this one figured out.
rec2020,also called BT2020, uses a a different color gamut.
So the colors in your scene will need to be adjusted for it.
Red RGB is 1,0,0
Red rec2020 is 1,0.1,0.1
Green RGB is 0,1,0
Green rec2020 is 0.1,1,0.1
Blue RGB is 0,0,1
Blue rec2020 is 0.1,0.1,1
Changing these makes rec2020 render red instead of black for me.
notes:
These are approximate colors.
This gets you close for aces and acescg also.
xyz uses even lower primary values.
Red xyz is approximately 0.27,0.11,0.10
Going to need a lot more experiments before I get it right.
Hopefully someone can write a script/plugin that converts color spaces.Doing all this by hand sounds like agiant pain in the backside.
edit:I'm also pretty sure this means that all textures and maps will need to be converted to the color space you want to use also.
ooops, deleted my test render while editing last post....
What does the monitor have to do with it? Serious question. Do I need an advanced typ of a monitor in order to use aces spectral rendering?
Right now, I am using a Dell Canvas connected via display port to my PC.
If the monitor is far from callibrated then colours and toens may lok very wrong. Almost any monitor should be roughly callibratable - even using one of the on-screen tools may give enough, though if someone is wanting to use a particular colour space I'd think they'd want to use a hardware callibration tool such as the Spyder.
Yes, definitely calibrated. I am using an ASUS ProArt 3290C that I calibrate monthly with a Spider Elite.
Thanks, I will give this a whirl and see what I come up with, I did notice shades of other colors also looking a bit *off* but it was most evident with Red as that just goes completely black.
Well, ... look at my renders
I used this collar pallete for the renders:
collar calibration - Suche (bing.com)
tone mapping is at default settings
As I understand it in the spectral color conversion color space you have to set the gamut of your monitor.
The ProArt Display PA329C should look fine enough because it covers 84% of REC 2020. But the pure red is probably out of the 84% coverage so it's out of gamut. You need a full REC 2020 monitor.
As for the Dell Canvas it's Adobe RGB so it's expected that goes out of gamut with REC 2020. While it renders fine enough with REC 709 because REC 709 and SRGB are very similar and included in Adobe RGB.
Makes no sense in my opinion to edit by hand the color palette to shrink REC 2020 to SRGB. Just select SRGB or REC 709 as output if you have a SRGB monitor. Then of course the monitor has to be calibrated as Richard says, but first the gamut must fit.
Aha, when I bought it, it was the best I could get for the money I had... Maybe I'll be looking at a new monitor this year... I figured 84% would be enough to "get me by" but maybe not, especially if reds look black (and I mean black as pitch, not just dark).
Even Wacom's top of the line model doesn't support more than Adobe RGB.
Can you post one of these blackened images? I would like to see how it looks on my screen.
(The only way to get non-sRGB renders out of Studio is with Canvasses.)
edited
The DAZ *.exr files have a higher dynamic range, but not more collar space. They are still sRGB.
Not true, as far as I know, if it was they wouldn't work as HDRs. They should be, as I understand it, rendered without tone mapping and then tone-mapped in the editor for human consumption.
I agree with Richard. As I understand it exr is in linear color space, that means all the possible physics values so an "unlimited" gamut. Think of it as the raw rendering buffer before color mapping. Then color mapping is the transfer function from the linear space to the output space, mostly srgb for normal monitors.
I opened the *.exr in Photoshop and I could edit as usual the exposure. Usually I dial it down to -13. I understand, that I am not able to see the whole collar spectrum at once, because of limited Adobe RGB, but I should be able to shift the spectrum then. That did not work. The black parts of the gamut pallet remain black, no matter what if I try the HDR toning or Hue/Saturation tool.
@JasonWNalley You may also check your monitor driver and connection to be sure it handles the rec 2020 space. I know hdmi 2.0 supports the rec 2020 space, don't know about other connectors.
Just tried rendering a red object on a couple of screens, and even on a rec2020 HDR screen it still renders red as black. ...so it's not the monitor calibration or capability!
nVidia have been tweaking the ODT for a couple of versions now and I would guess there's more tweaking to do.
I'm not sure I follow - black is black and can only be chnaged if you enable the Colourise option in whichever tool it is and adjust the black point to a shade of grey, so that it has a non-zero value. That has nothing to do with colourspace.
So its value is black, you are not just eyeballing it?
Not sure what you mean.
@Masterstroke The exr files work fine here in gimp. You may try disabling the tone mapping in iray but it doesn't seem to make any difference here, has it is expected since exr comes before tone mapping. I'm on daz studio 4.15 though to avoid the new iray issues so can't tell for 4.20.
Anyway it makes no sense to use rec 2020 if you get an adobe rgb monitor. But again exr should be independent of it, unless bugs.
edit. Test exr attached and tone mapping by gimp. Had to use zip because the forum doesn't allow to upload exr.
edit. You can upload your exr for me to try in gimp. Make it low res please as 1280x720 so it's small in size.
@prixat Unfortunately I don't have a rec 2020 monitor for testing so I can only guess here. It is also possible that there are bugs in daz studio. For sure it makes no sense to use the rec 2020 output on a srgb monitor.
I would say it's within Iray.
With Spectral Rendering an Input Device Transform (IDT) converts all textures and shaders to the extended colourspace you have chosen.
The renderer churns away in the extended colourspace.
An Output Device Transform (ODT) converts it back to something we can see, a normal sRGB preview or PNG or JPG etc.
Getting the IDT and ODT right is quite important.
I think my GPU is slow enough that I see a glimpse of the overexposed, ridiculously bright render of the red object just before the refresh snaps in and turns it black. Which suggests it's an ODT problem.
Just to elaborate on IceCrMn's fix.
It's easier to see in HSV, it's the Saturation that seems to have a maximum value, above which it just flips to black.
for ACEScg max. Saturation values:
R-222 G-203 B-214
for rec2020:
R-223 G-226 B-214
@prixat Just to be clear, spectral rendering is another thing entirely and has nothing to do with rec 2020.
Alright, so this conversation has been crazy confusing with everyone sharing what they think it is... So let me try asking this question differently.
My goal is to render video and grade it in HDR. My thought was to render it in the colorspace I would be grading in, which is BT2020, this seems to not work because the colors don't render as they should (reds rendering black is most noticeable) (this applies to stills and video).
I was hoping to render in Iray straight out of DAZ using Iray or Octane, but I can also use Blender +Cycles or C4D+RedShift if that's a better option... I'm open to suggestions.
So I guess what I am really asking is:
Is it even possible to render HDR video in the BT2020 colorspace using DAZ + Iray?
-If so, how?
-If not, what is the easiest method for achieving this?
@JasonWNalley The solution is simple just render in exr that's linear space, then post process to anything you want.
Ok, just a couple of questions to make sure I understand this.
1) In this video he's talking about bringing something into resolve, and first converting it to Linear, then doing editing, then putting it back into the proper color space you desire. Yes? Do I have that right?
2) provided I understood correctly and question 1 is a yes, then my next question is, how do you render in exr in DAZ? Do you just turn off spectral rendering and render it out? Or is there more to it? I saw some people talking about using canvases above, but I only ever rendered with canvases 1 time, and that was a long time ago. Does the resulting image from say a "Beauty" canvas come out in linear color space?