To speed up the process of lighting your scene with an image, you can use the Image Based Lighting render pass preset. Creating a new render pass using this preset automatically applies the Environment shader to the pass and enables final gathering in the render options. Of course, you can modify the pass to alter the image based lighting effect or limit the number of objects that it affects.
For more information about render passes and how to customize them, see Passes & Partitions [Rendering].
From the Render toolbar, choose Pass Edit New Pass Image Based Lighting.
When prompted, specify whether you want to use an existing image clip or create one from file.
Once you select an image clip, a new render pass, called HDRI by default, is created and set as the current pass.
Click the Pass Shaders tab and adjust the Environment shader settings (as described previously) until you're satisfied with the results.
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