Saved Image Looks Different Than Frame Buffer

[Radim Razzak]

ToneMapControl map is bit finicky.. anytime you make framebuffer change, you have to restart the render for it to negate everything.

Yes, I knew that if you change the tone mapping parameters during the render, it would affect the background image. But that's not my case. In my case, that LUT and the tone mapping parameters do affect the background image right from the beginning.

That is particularly issue with LUTs and when and how you use them in process. Unless you're making an animation you might be better off adding that LUT in Photoshop.

Please correct me if I'm wrong, but if I render the image with its background with no LUT or Tone mapping, and apply them afterward in PS, the result would be the same, right? Or you meant that I'd need to apply a mask in PS in order to avoid that from happening?

(Btw, reflections/refractions for compositing will be added in upcoming Corona version).

And what would be the right workflow until then? Could you explain to me please how would you do that? Thank you very much!

[TomG]

Can you share a grab of your setup, since the tonemapping and LUT should not affect the background when it is set to disable those for the HDRI in question. Thanks!

[Radim Razzak]

Here it comes: the original image from PS, the renders without and with the LUT applied and the settings. It's not the interior render I was talking about but I think on this example it's more evident. I reset the corona values to the default (switching to the scanline and back) but it wouldn't actually do anything.
Thank you for your help!

EDIT:
I forgot to mention that the background image is connected to the Direct visibility override slot, I suppose that it doesn't matter, does it?

[TomG]

I haven't tested a set up like this, but I believe the Tonemap control should be the last in the chain, and then the Tonemap goes into the Environment or Direct Visibility override. So it would be bitmaps into Corona Select into Tonemap.

As things are at the moment, the Corona Select is still set to be adjusted by the tonemapping, since it isn't going through a tonemap (but, haven't tested with a set up like this :) )

[romullus]

@Radim Razzak, did you read the warning in tonemap control texmap? It can't reverse everything. Exposure and most of tone mapping are not the problem, but i never had success in reverting LUTs, it just doesn't work.

[Radim Razzak]

I haven't tested a set up like this, but I believe the Tonemap control should be the last in the chain, and then the Tonemap goes into the Environment or Direct Visibility override. So it would be bitmaps into Corona Select into Tonemap.

As things are at the moment, the Corona Select is still set to be adjusted by the tonemapping, since it isn't going through a tonemap (but, haven't tested with a set up like this :) )

Thank you Tom, I tried what you suggested but unfortunately, the result is all the same.

[Radim Razzak]

@Radim Razzak, did you read the warning in tonemap control texmap? It can't reverse everything. Exposure and most of tone mapping are not the problem, but i never had success in reverting LUTs, it just doesn't work.

Yes, I read it. But then the question still stands: what is the correct workflow in the interior setup with a view to the interior through a window? Thank you!

[TomG]

I just tested in a simple scene, and it does indeed prevent the Tonemapping (haven't looked at LUTs, just a quick test with exposure) with either set up of tonemaps on the bitmaps through the select, or the select itself through a tonemap (though it's less setting up to just have the Corona Select go into the Tonemap).

As noted, not everything is reversible, which could be what you are running into here, especially with LUTs

[Radim Razzak]

I just tested in a simple scene, and it does indeed prevent the Tonemapping (haven't looked at LUTs, just a quick test with exposure) with either set up of tonemaps on the bitmaps through the select, or the select itself through a tonemap (though it's less setting up to just have the Corona Select go into the Tonemap).

As noted, not everything is reversible, which could be what you are running into here, especially with LUTs

OK, thanks for the explanation, Tom. Nevertheless, is there any workaround or my best bet is to render without the LUT and applied it afterward in PS to the masked geometry only?

[TomG]

Best bet as you say, if that particular LUT is not "reversing" fully, is to do it in post - you could apply the LUT in post, using masks so it isn't applied to the background part; or you could use alpha to just add the background in post, letting you apply the LUT in the VFB.

[Radim Razzak]

OK, I'll give it a try, let's see if I can solve that in post using masks then. The other approach you mentioned (rendering without the background and using alpha in PS)... I already tried that and unfortunately got several issues with reflection/refraction/translucency (even though I had the "Direct visibility override" checked and black color selected). Anyway, thanks a lot for all your help, Tom.

[n2graf]

MOVED TO GENERAL DISCUSION

(So, since Corona works internally with WideRGB, is this workflow accurate?:

1- Save the image of VFB in EXR 32bits float without any tonemapping,

2- Open the EXR in Photoshop asignin wideRGB color space and using proof colors in sRGB to visualize it while we are editing the image. (we asign wideRGb because is the raw of corona understandign that corona works with wideRGB, and because photoshop have more colors to prevent banding or clamping while editing). Convert to 16bit compressing highlight and making tone mapping.

3- Convert to sRGB (in perceptual or colorimetric mode) and if we are not happy with the conversion, go back and edit saturation in the areas that gamut warning of proof colors are pointing, to prevent unwanted changes with the conversion.

4- Save the image in a JPG file with sRGB profile.

5-Send it to client.

Is this the correct workflow for 32bits?

Thanks!<)