What the heck are backplates used for?

i’m trying to make a realistic image with an hdri, but the website i downloaded them from had backplates. so i tried looking around on the internet to see what purpose backplates use, but i couldnt really find anything. can someone tell me what they’re for?

(sorry if this is in the wrong category)

Backplates are just environment photos you load into your camera/background, so you dont have to create the environment yourself. Ofc your lighting has to match the backplates. Usually done with some fiddling or fitting Hdri’s.

You could for example load the backplate in as skytexture, and clamp the borders. (repeat)
so you get a wraparound for the basic lighting mood. But some additional work is then needed…

Id suggest looking at greg zaal’s awesome CC0 HDRi’s if you dont know them already:

ahh, ok. thanks!

Often you’ll find backplates bundled with hdr images and blurred hdr.
HDR: Less resolution, used for reflections.
HDR Blurred: Very low resolution, used for diffuse lighting - usually don’t have a real sun.
LDR Backplate: High resolution but only 8bit and in normal projection, used only for camera rays.

Showing HDR, whose size comes from bit depth rather than resolution, to camera, will especially if the camera zoom is high cause resolution issues. Switching to backplate, which has far greater resolution but only 8bit depth, resolution problems goes away.