CIE - option to apply LUT without hidden gamma transforms.

[piotrus3333]

This would make things so much easier for everybody:

[Avi]

Hi Marcin,

Can you share some use case to have the lut work in linear as compared to sRGB?

[maru]

Just to understand this better:
The result of applying a LUT in "Work in linear" vs "Work in sRGB" mode would be just a different appearance of the final output?

[piotrus3333]

use case: to use a lut file as it is intended to be used. lut takes a given number and converts it to a different number. it should be straightforward like that.

VRay's work in linear option is how luts work in every software imaginable. it is the default behaviour. everywhere. work in log and work in srgb options are added just to simplify things, so one can use just one lut instead of two.

what Corona does: it applies hidden gamma transform just before the lut and inverse gamma transform just after. so the lut is getting incorrect input.

why: well, long time ago somebody thought that Corona users were not able to grasp the difference between linear and gamma. user could apply the lut on raw (linear) render in Corona's vfb, save the raw render to a jpg (gamma corrected) and than in Photoshop open said jpg, apply the same lut and get the same result. obviously without realising that it should not give the same result - as the view transform in Corona's vfb is also hidden.

tldr: what I'm asking for is: Corona, please be professional.

[maru]

Thanks. The main reason why I was asking about the difference is that we treat LUTs in the VFB "just" as an effect to change the mood of the rendered image. Sorry for the unprofessional comparison, but pretty much like Instagram filters. That's why it should not really matter whether a LUT is applied one way or another. We have not received many reports like this, which of course does not mean that our LUT implementation is perfect, but we can assume it is generally accepted.
In case a user needs to perform some more advanced tasks using LUTs, they will probably save the output separately and open it in specialized software.

How I understand your request is that you would like to have the ability to use LUTs in a more technically correct way directly in the Corona VFB so that you don't have to use additional software. Is that right?

[dj_buckley]

We have not received many reports like this, which of course does not mean that our LUT implementation is perfect, but we can assume it is generally accepted.

Or because the users have assumed LUT's are already being applied in a technically correct way i.e. myself

When buying technical software as a professional business, I'd like to think it's as technically correct as possible behind the scenes.  We're not teenagers using Instagram, we're professionals using professional software so I just assume it's not coded as some sort of 'hack'.  Especially in the case of Corona, where half of your responses on here to peoples artistic issues are along the lines of 'it's expected as it's physically correct etc etc".

You drive home the point and priude yourselves on the fact that Corona is physically correct yet based on you're reply you're happy for it to not be technically correct for a quick visual buzz.  It's kinda contradictory.

[dj_buckley]

In case a user needs to perform some more advanced tasks using LUTs, they will probably save the output separately and open it in specialized software.

Also this is quite the assumption.  When paying advanced fees, it's not unthinkable to believe we should be able to carry out advanced tasks.  Piotrus3333 isn't asking for advanced, specialized use, simply asking for 'correct' use.

[piotrus3333]

How I understand your request is that you would like to have the ability to use LUTs in a more technically correct way directly in the Corona VFB so that you don't have to use additional software. Is that right?

yes, that is correct.

But if luts in Corona are just "instagram filters" why developers bothered with a very complete implementation of .cube lut format? something that for example VRay sadly lacks. LUT layer in CIE is a single most powerful tool there but this annoying design choice makes it harder to use efficiently. like a racing bike with stabilizers.. mind boggling.

maybe this will put things into perspective: you can do more with LUT layer in Corona than with ocio as it is currently implemented in VRay. wouldn't that make a lot of people happy?

all the waiting for tone mapping updates? why? that was not needed at all. everything was just sitting there unused for ages (since 2018). I think even devs forgot about the almost-perfect tool they made.

tldr:

please get rid of stabilizers, it's a racing bike

do you need "instagram filters" LUT layer or "better than ocio in VRay" LUT layer?

[Basshunter]

Even Vantage lets you apply your LUTs in linear:

[maru]

Hi all, thank you for your feedback. We now have this logged as a feature request.

Just a quick note: When making similar requests in the future, please provide more specific details and examples. This will help us better understand why you believe this feature is needed. Also, if you're working with workflows and pipelines related to color spaces and color management in your professional environment, you might find V-Ray to be a better fit for your needs. If you'd like to discuss your specific requirements and use cases, please feel free to submit a ticket here.

(Internal ID=1213995718)

[dj_buckley]

That's the second time i've seen "use vray" as a response to something.  Do I detect the slow phasing out of Corona?

"Also, if you're working with workflows and pipelines related to color spaces and color management in your professional environment"

I'd say that's 99% of your users, including the one man army freelancers.

[pokoy]

Hi all, thank you for your feedback. We now have this logged as a feature request.

Just a quick note: When making similar requests in the future, please provide more specific details and examples. This will help us better understand why you believe this feature is needed. Also, if you're working with workflows and pipelines related to color spaces and color management in your professional environment, you might find V-Ray to be a better fit for your needs. If you'd like to discuss your specific requirements and use cases, please feel free to submit a ticket here.

(Internal ID=1213995718)

While I understand that you internally regard Vray as the technically more 'advanced' and versatile engine (and Corona for some reason is archviz-first) for some of us it's not an option to switch to Vray and never will be. Things like technical ground truths like color management or the above request shouldn't be regarded as advanced features but rather as standard features users expect to work. Corona has added quite a few features that users rely on that originated from 'advanced' use cases and it's what makes the engine a serious tool in various fields... and it's far from not being a professional piece of software.

[piotrus3333]

Hi all, thank you for your feedback. We now have this logged as a feature request.

Just a quick note: When making similar requests in the future, please provide more specific details and examples. This will help us better understand why you believe this feature is needed.

(Internal ID=1213995718)

please, tell me how do you imagine „more specific details and examples” than this:

use case: to use a lut file as it is intended to be used. lut takes a given number and converts it to a different number. it should be straightforward like that.

[piotrus3333]

Hi all, thank you for your feedback. We now have this logged as a feature request.

Just a quick note: When making similar requests in the future, please provide more specific details and examples. This will help us better understand why you believe this feature is needed. Also, if you're working with workflows and pipelines related to color spaces and color management in your professional environment, you might find V-Ray to be a better fit for your needs. If you'd like to discuss your specific requirements and use cases, please feel free to submit a ticket here.
 
(Internal ID=1213995718)

and also if you consider this issue is related to a need for different colour spaces and colour management in Corona I think we still do not have an understanding.
it’s about simple math that Corona does wrong edit: incorrectly I mean.

[TomG]

Nope, no slow phasing out of Corona, just those pipelines have never been something Corona supports but V-Ray does (we're looking at pipelines used by VFX for example, for those where there are separate teams or even separate companies doing different parts of the pipeline, with end results that have be mastered for particular display devices etc.) Given that is what we mean, it most definitely is not 99% of our users :)

"(and Corona for some reason is archviz-first)" - that is always what Corona has been. It was built for that purpose, with Adam one of our founders coming from the archviz field with the insight that V-Ray did too much and an engine aimed squarely at archviz that removed the excess and was built for what archviz folks did daily would be much welcomed, with folks like Recent Spaces, The Boundary, AsymmetricA etc. being there as our testers and feedback cases for version 0.1 and onward. So it's not "for some reason", it is THE reason for Corona existing at all!

[maru]

@piotrus3333 please, no need to be disrespectful. Nobody is attacking you. We are simply asking for more informative reports in the future.

please, tell me how do you imagine „more specific details and examples” than this:

use case: to use a lut file as it is intended to be used. lut takes a given number and converts it to a different number. it should be straightforward like that.

and also if you consider this issue is related to a need for different colour spaces and colour management in Corona I think we still do not have an understanding.
it’s about simple math that Corona does wrong edit: incorrectly I mean.

Here are some ideas:
- You could have shown images with the same LUT applied in sRGB vs linear mode
- You could have told us in what specific other software LUTs are applied in linear mode
- You could have presented some evidence that indeed there is some "correct" and "incorrect" way of doing this

For reference, this website https://blog.frame.io/2019/08/12/luts-101/ says:

"LUTs have no way of knowing the gamma or gamut of an input image, nor even the ability to make an educated guess. They’re built by their authors to expect images of a specific gamma/gamut pair, for example Arri LogC/Arri Wide Color Gamut. This presents one of the main points of confusion when it comes to deploying LUTs. End users have to not only understand that a LUT has specific input needs, but also how to determine what those needs are. Frustratingly, this is not always easy. If the author doesn’t either tell the user personally, or notate this information somewhere inside the LUT, we’re left with guesswork and subjective compensations in the grade. This can lead to glaring problems, as well as subtly devious ones, such as small artifacts that go unnoticed until it’s too late, or clipped highlights or shadows."

This means that if we introduce an additional "Work in linear" mode, that might become confusing to users, who do not really know how exactly a specific LUT was authored. Remember that Corona is about simplicity.

We are always interested in how exactly you are using features in your workflow. Why do you need 100% accuracy? You can help us make the report better by explaining to us what exactly you would like to see and, most importantly, why.

To sum up: "it is intended to be used that way" or "it's simple math" or racing bikes and stabilizers are not valid arguments

[dj_buckley]

Nope, no slow phasing out of Corona, just those pipelines have never been something Corona supports but V-Ray does (we're looking at pipelines used by VFX for example, for those where there are separate teams or even separate companies doing different parts of the pipeline, with end results that have be mastered for particular display devices etc.) Given that is what we mean, it most definitely is not 99% of our users :)

The comment made was "if you're working with pipelines relating to colour spaces and colour management" in which case that is 99% of your users, even if it's as simple as calibrating our displays or authoring our final jpegs in specific colour spaces, or shooting our own backplates and authoring our own textures etc.  We're all working with colour management and colour spaces to some degree.  We don't all have to be producing Hollywood blockbusters to be taken seriously.

So it's important that the software we use isn't making things more difficult and works as expected.  If you're not interested in proper colour management etc then don't bother with it at all.  But when you're implementing things like ACES CG for the rendering colour space, and introducing ACES OT tonemapping operators then it would be good to see a full accurate colour management rollout, especially now your host software is taking it seriously.

A simple search for 'Colour Management' or 'sRGB' or 'ACES' here on the forums will show you how popular colour spaces and colour management is for a good chunk of users.

I also notice 'Colour Managed Workflow' has finally been moved to "In Development" for V11, so why suggest 'go use Vray' rather than just "hopefully coming in V11"

Also for what it's worth, "go use VRay" might have been an option this time last year, but not that long ago, a lot of us ended up tied into annual contracts ;)

But back to the original issue .... the original post isn't about Colour Spaces and/or Colour Management.

[piotrus3333]

Nope, no slow phasing out of Corona, just those pipelines have never been something Corona supports but V-Ray does (we're looking at pipelines used by VFX for example, for those where there are separate teams or even separate companies doing different parts of the pipeline, with end results that have be mastered for particular display devices etc.) Given that is what we mean, it most definitely is not 99% of our users :)

one example: Corona supports 1D shapers in 3D .cube luts. Vray does not (it supports maybe 10% of .cube file capabilities)
one .cube lut in Corona can do all the color operations available in VRay’s vfb and more, because you can stack it. suprised?

"(and Corona for some reason is archviz-first)" - that is always what Corona has been. It was built for that purpose, with Adam one of our founders coming from the archviz field with the insight that V-Ray did too much and an engine aimed squarely at archviz that removed the excess and was built for what archviz folks did daily would be much welcomed, with folks like Recent Spaces, The Boundary, AsymmetricA etc. being there as our testers and feedback cases for version 0.1 and onward. So it's not "for some reason", it is THE reason for Corona existing at all!

one funny story: few years back one of the founders of one of those three mentioned studios could not figure out how to move grading from his post production tool to Corona (via lut) just because this unusual way Corona does luts. would you call it a feature well designed? in everyday work it brings the necessity of having “Corona” version of every used lut and lost precision within blacks and shadows. what a waste of otherwise great .cube implementation.

[piotrus3333]

@maru
the quote you posted explains exactly why what Corona does is not correct.
not correct as in: everywhere I know it is done differently.

again, not disrespectful, just trying to get through lack of understanding.
(I was really hoping racing bike metaphor would work..)

another try:
the lut file says that colour X turns to Y.
Corona turns X into Z.
at least questionable, right?

[piotrus3333]

@piotrus3333 please, no need to be disrespectful. Nobody is attacking you. We are simply asking for more informative reports in the future.

Here are some ideas:
- You could have shown images with the same LUT applied in sRGB vs linear mode
- You could have told us in what specific other software LUTs are applied in linear mode
- You could have presented some evidence that indeed there is some "correct" and "incorrect" way of doing this

- images attached, VRay vs Corona, I hope this shows how “uniqe” Corona’s approach to luts is.
edit: yes, view transform in VRay matches that of Corona in this example. yes, "log" mode also does not match.

- every other software you can imagine. some will give you (like VRay) options to do some transforms before or even before and after lut (exposure adjustment for example). Corona is unique. again.

- chapters 6.1 and 7.1:
https://kono.phpage.fr/images/a/a1/Adobe-cube-lut-specification-1.0.pdf

[piotrus3333]

Hi all, thank you for your feedback. We now have this logged as a feature request.

(Internal ID=1213995718)

Ok. this is sorted now. I guess no need to keep the request opened.
Thanks.