Tamron 28-75 bought new: ¿worth calibration?
My gut feeling is that you will get the lens/camera back and have the same results. The best sharp photos are taken a stop or two down from wide open and by avoiding the extreme ends of the zoom. Your first photo violates both of those techniques.
Actually the fine print in the photo is not too bad, so there might be a little flare involved with the back light sign. How about some daylight shots taken of text using tripod, mirror lockup, cable release.
Can more folks weigh in on this?