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Using the method described on stack exchange here to create a shadow catcher and with Filmic render view under color space enabled, the background with shadows divided by a clean background with no shadows does not generate white. Instead, a very light grey is created where there is no shadow. This should be white so the shadow layer can be multiplied onto the composite.

However, when default render view under color space is used, the grey becomes true white, suitable to multiply with.

Therefore, I suspect there is some gotcha with exporting log color images out of blender and photoshop understanding them.

The foreground objects and the shadow layer both need to be exported to photoshop.

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  • $\begingroup$ What you call " white" is at a different value when you use the filmic blender in the color management. read: white background with filmic blender and most importantly this link: render with a wider dynamic range to understand how filmic blender works. It is perfectly possible to get "white" with filmic blender, you just need higher values. $\endgroup$ – cegaton Feb 24 at 2:59
  • $\begingroup$ I'm starting to understand more of filmic, however in this case, i'm color mixing with division the same color. This should produce white, at least with respect to display referred data. What am I not understanding here? $\endgroup$ – Boris N Feb 24 at 7:13
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the background with shadows divided by a clean background with no shadows does not generate white.

If you are dividing any value by itself the result will be one: $\frac{X}{X} = 1$

The standard sRGB transform will display white when the scene value reaches 1enter image description here

But "white" doesn't live there any more if you are using filmic blender's color transforms.

"White" is not equal to 1, 1, 1, White is somewhere around 16.29174024 in scene referred values (and operations before the color management, like nodes in the compositor, are done with scene referred data. The color transforms to create display referred images out of that data are done at the very end of the pipeline).

Filmic blender uses a much wider dynamic range, Using the filmic blender transforms you need a much higher value to reach "white", most likely you would need to scale the result of that division by 16.29174024 with a multiply node to fall within the parameters that work with filmic blender.

enter image description here

To understand what filmic blender does and how it maps the scene's values to the displayed image please read the following link: Render with a wider dynamic range in cycles to produce photorealistic looking images

and https://github.com/sobotka/filmic-blender

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  • $\begingroup$ Ok. I understand what data set is used when now. Follow question then, would the shadows be darker than they should be due to the division working on scene referred data and hence the need for scaling up by 16 afterwards (at least when exporting display referred data such as with a png)? $\endgroup$ – Boris N Feb 25 at 2:27
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Through trial and error and a couple blender filmic answers, the solution to exporting filmic/log color out of blender is to use the EXR format with float full color depth.

output settings

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  • $\begingroup$ I assume EXR's can export log color due to their ability to store high dynamic range data, but I am not exactly sure. $\endgroup$ – Boris N Feb 23 at 4:05
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    $\begingroup$ It works not because of the dynamic range of EXR's, but to the fact that when you export as EXR you are keeping your data as linear. When you export as EXR you are efectively bypassing the color transforms in the Color management. And works in other software because you are doing the compositing using display referred values. $\endgroup$ – cegaton Feb 24 at 17:58

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