Indoors or outdoors? How close to the cars? How much of an issue is barrel distortion for you? Hand held, or tripod?
The 80D is the “problem” with this question. It is an APS-C body, and there are a couple of “gaps” in the Canon AF-S lens lineup for APS-C sensor camera bodies. I think a nice sharp, rectilinear wide angle lens would be ideal. It would also need to be fast, preferably f/2.8, or even faster.
On a full frame body, the EF 24-70mm f/2.8L II USM would be a good choice, indoors or outdoors. The closest equivalent lens for an APS-C lens would be the EF-S 17-55mm f/2.8L IS STM lens, which is not as well built as the 24-70 “L” series lens.
While not as long as the above two lenses, the EF 16-35mm f/2.8L II USM, or the EF 16-35mm f/2.7L III USM, would work fairly well on the APS-C body 80D. You might consider a fast prime, f/1.8 or faster, between 16mm and 35mm, too.
The above photo was taken with my current favorite lens, the EF 35mm f/2 IS USM, on an APS-H body.
"...what lens they would use for car show photography..."
Not a particularly difficult subject so just about any lens you might have will do just fine. As a matter of fact the question might be what gear to use? And the Canon PowerShot G1 X Mark II Digital Camera is a fine candidate. Great camera with a great lens all in a small package easily carried all day long.
Actually indoors and out, but mostly close quarters indoors. Hand held
I think the EF 16-35mm f/2.8L II USM, or the newer Mark III, version will be a good lens. If you had a full frame body, I would recommend the EF 24-70mm f/2.8L II USM lens, but it may get a little long in close quarters.
Assuming that you’re not using a flash, then you will want a fast lens, perhaps even a fast prime, faster than f/2.8, IMHO.
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