All of these scenes are 100% lit with HDRIs, a technique called image based lighting (lighting based on an image). The only thing that was changed between them are the background HDRI. What is HDRI you may ask? Well, HDRI is an acronym for High Dynamic Range Imagery.
And what is that? It is an image format (.hdr) that contains extended information between the brightest pixel and the darkest pixel. For those of you familiar with stops (in photographic term) a typical HDRI can reach 22 stops and a typical jpeg can reach a measly 11 stops on average.
To put that into perspective, 11 stops equates to 2048 times brighter between the brightest and darkest pixel (2 to the power of 11). Compare that to 22 stops: 4,194,304 that’s more than 4 million times brighter.
And 2,048 times more dynamic rage than a jpeg image, his image format can fit luminosity from the deepest shadow all the way to anything as bright or brighter than the freaking sun!!!
Oh and it’s also a spherical image, meaning that light can be wrapped around your model and all reflections are true and accurate.