Testing focus at 5 meters

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sirhawkeye64 Senior Member • Posts: 2,167
Testing focus at 5 meters

So I have a Tamron G2 70-200 lens and I have it calibrated for close focus (1m). I'm using a setup with a flat Reikan FoCal target (looks like a QR code which is maybe what it is), and a ruler next to it at a 45 degree angle. Both are well lit so AF can lock on.

Again, I'm using a similar set up to what Abbott uses in this video:

https://www.youtube.com/watch?v=xtNXtudLPbI

The ruler is still at 45 degrees from my close focus tests, which IMO at 16 ft away looks more flat from the perspective of the camera, especially at 70mm.

In my initial tests, my lens was showing significant back focusing. At 200mm the target is sharp and the DOF distribution (around the point of focus on the ruler) is acceptable. But when I go to 135mm and 100mm, it severely back focuses. At 135mm, I have adjusted the lens down to -20 with the tap-in console but there is still significant back focus.

Do I need to adjust the angle of the ruler up for testing at 5 meters (16.4 ft)?

(I'm doing this all at f/2.8 by the way so I can easily see DOF even though I may not shoot at this aperture much, in practice).

 sirhawkeye64's gear list:sirhawkeye64's gear list
Nikon D7100 Fujifilm X-T2 Nikon Z6 Nikon AF-S DX Nikkor 35mm F1.8G Nikon AF-S Nikkor 24-70mm f/2.8G ED +14 more
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