I use it on a tripod when I have used the live screen preview (Canon 70D) and zoomed in to where I want the focus and it's not in focus enough.
This might be my problem though. May have dropped the camera from a small height onto the lens, years ago.
I got bitter and left around the smugmug time.
My photography priorities have changed a bit since then and I don't really feel the need for Flickr or a site like it anymore.
Good for them if things are improving for them though! ๐