How to check focus on lens?

[SuzukiGS750EZ]

Hey guys. I didn't know where to post this and assuming you all shoot with a long lens... Here goes.

I have a Tamron 150-600mm g2 on a Canon 80d. I also have the tap in console so if any adjustment would be made it will be in there. When the lens was new a year or so ago I had the lens and body sent to Tamron to be "married" if you will. I had a knee surgery and life take over and hadn't shot in a bit. Recently got back out shooting and the lens seems soft at 600mm at distance but I don't remember it being that way, though I could be wrong.

How can I check it at home simply without software or targets? Is this possible to do in a room?

 

[Fujidave]

I don`t know if it helps or not, what I use to do with my Sigma 150-600mm was just take shots of the garden birds at full zoom.

 

[HavToNo]

I had the the first version of that lens and a 70D at the time and I found that anything over 500 was soft. I don't know about the g2 version except what I"ve read online, that it's a little soft at 600.

 

[KmH]

focus chart - Yahoo Search Results