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Extreme image difference exporting Blender to Fusion?

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Dazzer

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Extreme image difference exporting Blender to Fusion?

PostThu Dec 26, 2019 12:28 am

Hi folks,

When exporting an EXR from Blender to Fusion, i'm getting a complete change in image, and i'm trying to work out why.

Please take a look at the two images below. The first is how my render looks in Blender. If i export a jpg or an mpeg, it also looks like this.

The next image is how it appears in Fusion. So, the subtlety of the glow (called "bloom" in Blender) is gone, it's like i've maxed up the contrast to 100%

Does anyone have any ideas about why this might be or how i could export from Blender and keep my image 100% the same when bringing it into Fusion?

Obviously you don't know what render settings i'm using in Blender, but i'm not doing anything special, i'm using the stock settings and not tweaking anything.

Thanks in advance and happy Xmas!

light box blender.jpg
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fusion exr import.jpg
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Bryan Ray

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Re: Extreme image difference exporting Blender to Fusion?

PostThu Dec 26, 2019 2:09 am

An EXR will be rendered without the transfer curve that makes an image appear normal on the screen. Blender's render buffer has a LUT that converts from lin to sRGB to match your monitor. Likewise, a jpeg or other image is assumed to be intended for final viewing, not compositing, so it gets the sRGB color space conversion baked in.

In Fusion, if you turn on the viewport LUT and set it to convert from "No Change" to "sRGB," the EXR should look just like the rendered jpeg (with the LUT turned off).

Untitled.jpg
Untitled.jpg (88.98 KiB) Viewed 298 times


In this image, I've circled the LUT you need to turn on, the Edit button that lets you modify it, and the sRGB setting you need to get the correct output.

edit: Oh, and that grid icon above the pop-down menu is the one that activates the LUT. If you're using Fusion 9 it's a little clearer since the button just says LUT, but it's at the bottom of the window instead of the top.

edit2: Once you're done with your compositing, you'll probably want to convert your output to sRGB or Rec.709. You can do so with a Gamut node, which works just like the GamutViewLUT above. Put it right before your Saver or MediaOut to convert the linear composite to apply a transfer curve that will make the image viewable in other software. Unlike Blender, Fusion won't automatically assume anything about color space when you choose the output file type—it trusts the artist to know what they're doing.
Bryan Ray
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Dazzer

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Re: Extreme image difference exporting Blender to Fusion?

PostThu Dec 26, 2019 5:37 pm

Thanks Bryan!

Your suggestions got me 50% there, but there's still a considerable difference with what i'm getting in Fusion compared to a direct render (to mpeg) out of Blender.

I did some poking around in the Blender render settings and there's a setting called "view transform" that's set to "filmic". If i change this to "standard", then tweak my image to try to get back to the same image as before, the EXR (in Fusion) looks a lot closer to the render.

However, there's something really nice about how it looks in Blender with "filmic" turned on.

A bit more hunting around the interwebs tells me that Filmic is Blender's implementation of ACES, and that i need to use a LUT called OCIO in Fusion, however this is currently broken in Fusion.

It's all very technical, so i've probably garbled the details though!

Maybe i need to use a different format to export that'll "bake" in the look to the file? I'm not looking to do photo-realistic stuff, i just want to be able to take my images over to Fusion for compositing, so as long as a format supports an alpha channel and is lossless, i should be good to go?!
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Re: Extreme image difference exporting Blender to Fusion?

PostThu Dec 26, 2019 7:01 pm

I've used png files from Blender to pretty good effect, but YMMV.
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Dazzer

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Re: Extreme image difference exporting Blender to Fusion?

PostThu Dec 26, 2019 8:20 pm

Thanks! ............ i tried a PNG render, and it is indeed much better, i'd say 98%.

But (and i'm also seeing this in the images you posted) it's somehow a little less warm and the glow is still just a hair nicer in Blender.

I tried tweaking it to compensate in Fusion and couldn't quite get it to pop like it does in the Blender render!
Last edited by Dazzer on Thu Dec 26, 2019 8:26 pm, edited 1 time in total.
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Bryan Ray

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Re: Extreme image difference exporting Blender to Fusion?

PostThu Dec 26, 2019 8:26 pm

Filmic isn't ACES and has nothing to do with it, though they're often used in tandem. There's lots of bad info out there, unfortunately. Turning Filmic Blender off gets you closer to an ACES pipeline because it preserves linearity, but there's a lot more to it than just that.

You can apply the same (or a similar) Filmic tonemap in Fusion. The simplest way would be to use Reactor to download the RSPhotographicExposure macro. It was intended to mimic the film exposure tonemapping available with the Redshift render engine, but it has a mode for Filmic tonemapping instead, which I think is the same algorithm as Filmic Blender (though I haven't actually looked at what Blender is doing—I have assumed it uses the well-known technique described by Jon Hable).

edit: Oh, and there's nothing broken in Fusion's OCIO implementation. You just need to make sure you have a config file that contains the LUT you want to use. I haven't looked very deeply into that; I just use the ACES-approved 1.0.3 OCIO config, which doesn't contain Filmic Blender. Thus the macro I reference above.
Bryan Ray
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