How to Color Balance your HDRI?

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white balance hdri

How to Color Balance your HDRI?

For hdri map colour correction, I highly recommend you to use Photoshop. Please download and open FREE_HDR_103 hdr map from here and open it in Photoshop. For this tutorial, I am using Photoshop CS6 as it is the latest version available without subscription-based rental.

1. Open HDRI Map in Photoshop

photoshop exr layers prompt
As we are not working with OpenEXR layers choose whatever option and click OK.

2. Enable 32-bit Exposure preview slider

Click OK and in the bottom left corner switch little slider to 32-bit Exposure. Now when you move slider left or right you can darken or brighten hdri image preview.

If your hdri is too dark or too bright, and you want to fix it, you have to use Image > Adjustment > Exposure.

Enabling 32-bit Exposure slider in Photoshop

3. Set-up reference environment

I use Blender Cycles engine for tuning up my hdri map, as this is a software is free so available to everyone.

  • Simply start a new project with default cube, delete a lamp,
  • with Node Wrangler enabled, CTRL + T to add new environment texture in Shader Editor,
  • ALT + SHIFT + Z to hide Overlays. That’s it.
blender cycles hdri tuning
To my eyes there is too much green tint on Cycles preview

4. Back to Photoshop for hdri color correction

Create a new adjustment layer Channel Mixer and tune it to your needs. Testing hdri map file produces way too much green tint as it can be seen on reference scene screenshot, mostly because it was shot in the middle of a grassy meadow, grass can be seen almost everywhere around. In this example, I need to set Output Channel to Green and decrease Green value to 91%. Make sure that you have a backup of .exr file and overwrite the original file with command Save As and default compression method.

Simply hdri map white balance correction in Photoshop CS6

5. Blender – preview hdri map once again

In shader Editor, select environment texture and reload it using ALT + R shortcut. if you can’t see difference, turn off Cycles preview and switch it back on.

On the left not tweaked hdri map test scene. On the right with Greens desatured down to 96%. Cube is too much red, but hdri in the back look nicer.

As you can see on the test renders above, Blender’s default cube looks more natural on render where original hdri map was used, but the background is a way too much green. Background hdri looks better on the right side to my taste. So let’s combine those two hdri maps for the final scene using Blender Cycles shading.

6. Create camera visible only envrionment in Blender Cycles

Using two hdri maps, original and tweaked one, we will set one to be visible only to Camera and the second one for everything else (reflections, shadows etc). Following node scheme is self-explanatory. If you need more contrast in the light, simply add Gamma node before Background Node.

Blender Cycles node setup for camera visible environment hdri texture
Cycles environment corrected hdri maps
Test scene rendered using two hdri maps. Green tone was removed from background, camera visible envrionment

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