Testng a used Tamron 24-70mm help.

[Lance B]

Don't use a chart or test subject at 45 degree angle as this just puts too many variables into the mix. The issue is that the actual focus point may not be perfectly in the focus square of the viewfinder and when you test it on a 45 degree angle, then is is difficult to ascertain whether you have the exact point of focus. Use a set up like this:
https://www.ebay.com.au/p/LensAlign-...1542533&chn=ps

You just need a flat target with something the lens can focus on reasonably in line/parallel with the camera sensor, like some writing on the side of a box, and then put a ruler at a 45 degree angle next to it as this will give an indication of how for front or back focused the AF is. You can see the focus targets each side of the 45 degree pattern on the linked to Lens Align tool. This then removes any slight misalignment of the actual focus sensor being slightly out of alignment with the actual focus indicator in your viewfinder. Trust me, it is a much more accurate method to ascertain AF accuracy.

This is my home made set up and I have tested my D850 + 105f1.4E @ f1.4 specifically to show you how it can be done.



I focused on the area "CON" of the word "CONNOTE" on the box and the 250 mark of the ruler was set on the plane of the front of the box where the writing is and as you can see, the accuracy was spot on.

Here is a crop of the focus area.



Looking at your original photos, it looks reasonably accurate for AF and quite sharp. However, I think that a home made focus test such as that I have shown would be more beneficial and costs almost nothing!