Focusing thought....flawed or obvious?

So the other day I bought a lens that had massive front focusing, so much infact that I was unable to correct it in camera, so I sent it back and got me a refund.

But, while I was looking into figuring out how and why it was front focusing a focusing techneque occurred to me, I tested it and it seems to work.

1 - set lens on tripod,
2 - set center focusing point
3 - focus on something (but do not hit the shutter button)
4 - switch to live view
5 - zoom to center point and see how close the focus is to being right.

You can test how good the focus is be giving the focus ring a small turn both ways - if the image becomes sharper at any point when you manualy focus via live view then it logical to think your focus is off and you need to apply some in camera AF Microadjustment.

If you give the focus ring a turn and its gets worse you know you lens is focusing correctly.

I tried this at a bunch of distances (in my living room - so I admit its not a real world test) but it seemed to be a pretty good indication of how well a lens in focusing.

this is pretty much how u mf adjust and test with the software provided by canon

You've described how I do a very fast focus check, especially if I'm buying a used lens.

I embellish a bit at home, including hooking up a computer to make it easier to download images and really pixel peep. I've also started to use a LenAlign Mk II.

One of things I have to watch out for is to avoid moving the camera and target while I do my tests to maximization respectability. So I need to use a very steady tripod, wired shutter release, mirror lockup, etc.

That's pretty much what i done when i picked up my 50/1.4 & before that with the 85/1.8. Oh & the 50/1.8 that the 1.4 replaced

I don't like to get too scientific over it