Let’s say you happen to render against a backplate (or example a photograph) and nest the backplate in a CoronaOutput map with ‘Affect by tone mapping’ set to off to compensate for postproduction settings AND use a LUT. Now if you stop the render and rerender, funny things happen to the backplate because it tries to compensate LUT as well. I think this is absolutely wrong. LUT should always be considered a final grading and should not be considered by CoronaOutput map at all. The current behaviour forces me to switch LUT off when starting a render and enable it only after the rendering has started.
Let me know if you need image examples, it’ll make very clear why I think it’s wrong.
I mean the LUTs you apply in the VFB, on the final image.
I don’t even know why there’s a LUT option in CoronaOutput map, I’m using LUTs for final grading so applying the LUT solely to the background wouldn’t make any sense anyways.
So here’s what happens, I guess it’s way easier to understand with images.
General setup: backplate is nested in a CoronaOutput map, ‘Affected by Corona VFB tone mapping’ is disabled, used in the Direct Visibility Override slot in the renderer’s Scene tab. Pretty much the standard workflow for rendering against backplates.
Image 1 - Original render
Image 2 - LUT applied
Image 3 - Render is stopped and re-rendered (everything is left as it is, nothing has been changed)
This behavior is wrong imo. I should be able to obtain the same result as in image 2, instead the colors get messed up.
In other words, LUT applied in the VFB should never be take into account by the CoronaOutput map so we actually can use it as a final grading step. Whatever the LUT field in the CoronaOutput map does has nothing to do with what happens here.
I thought that there was already another thread about this, or a discussion in some other place. Looks like I was wrong, sorry. I’ll look into this and return to you a bit later, sorry, there is just so much work to be done!
No worries! I only wondered if I’m the only one thinking this needs to be corrected. I hope it will because working with LUTs is problematic using backplates with the described workflow.
I agree. But since I don’t think we’ll see an additional color correction map anytime soon (I may be wrong, though), we need the current behavior to be corrected.
Regardless of why the CoronaOutput map is hard to understand for beginners we need it to handle LUTs correctly either way, the example above demonstrates this well, it should never produce false colors.
