Relighting your renderings in post

Started by DriesV, November 18, 2013, 11:36:14 AM

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A repost of a comment in one of my Amazing Shots topics.
I thought it made sense to put it here too, for reference.

Here's a tip for a relighting technique in post using 32 bit images. It really shows the benefit of working with physical lights.

Here's a rundown of my process:

  • Set up your scene in KeyShot with all your lights enabled. Tweak your lights until you reach the sweet spot for your beauty shot. This will be the starting point.
  • Make individual renderings for every light source in your scene. E.g. If you have 2 area lights, make a 32 bit (EXR) rendering with only one light enabled and make another with the other light enabled. Do as many renders as you have lights ('light types') in your scene. Render out those individual lights that you want to be able to control in post. Remember to render to a 32 bit image!
  • For the above using the render queue can significantly speed up/improve workflow.
  • Import all your finished EXR's into a 32 bit capable image editor (Photoshop) and put them as layers in one document (TIP for Photoshop: File > Scripts > Load Files into Stack...).
  • For each layer, set blending mode to 'Linear Dodge (Add)'.
  • Add Adjustment Layers for each image layer. I suggest -at least- 'Exposure' (light brightness control) and 'Hue/Saturation' (light color control) for each layer. It's also a good idea to add a few global Adjustment Layers on top to control the image as a whole.
  • I suggest putting an image layer and its corresponding adjustment layers in a folder, so lights can be easily toggled on/off with visibility of the folder.
  • Play with visibility of light, brightness of lights, hue/saturation of lights, global adjustments... The range of images and lighting variations you can achieve is really quite astonishing.
  • With all light layers enabled, the result will pretty much look like your beauty shot in KeyShot.
This is a really powerful and flexible way of working with KeyShot's physical lights.

I attached a sample PSD working document with one of the scenes I posted above. Have fun experimenting!




Here's an updated resource package. It contains the original KeyShot scene and an updated Photoshop working document (higher resolution and better quality renderings).

Have fun!



Esben Oxholm

Great technique. Very flexible way to adjust your lightning in post. Thanks for sharing :)



Arian Shamil

Dries Thanks for these tips :)
Thanks you very much!
Ciao & grazie