Is 3 seconds too fast? It's a snap shot from a Unifi protect camera so it's local.
Some context would help.
Are you referring to an image tile on a dashboard?
Yes, sorry I should have said that.
I have used a 1 or 2 second refresh rates for images from one of my IP cameras (a Hikvision) on a local dashboard and it seemed to be fine.
I got away from realtime stream on sub stream - instead I use triggered images on main stream. push it instead of pull it!
I wouldn't worry about the speed. The image doesn't go to the HE hub so 1 sec is fine. I have 8 images at 1 sec before. Now I use real time stream video on the image tile.