How do I "sync" hard drives / copy files from one drive to another without duplicating them?

Hi, Is there a way to sync to hard drives? I'd like keep the same data on two hard drives (one as a backup), perhaps by coping files from one hard drive to another without duplicating them.

Background:

I shoot a lot of photos and store them on an external hard drive that I travel with. I keep a second hard drive at home with the same files. (I intentionally do not use Time Machine, in part, because the images are linked to a Lightroom catalog.)

I copy the files from one drive to the other every week or so. Lately, I've had to manually select the folders to copy. The problem with this: It leaves room for me to miss copying some folders.

In the past, I was able to drag and drop entire folders. Finder would then offer to only copy the new files. I'm not sure if something in MacOS changed or if I just forgot how to do this. Is there a way to do this?

Or is there another method to sync hard drives without re-writing all of the information, which would take hours?