Focus not even across the frame

[acho]

I have 90 degree camera. Managed to focus it somehow good at the cented of the frame but it goes out of focus by much near the edges of the frame /gradually/.
Is this normal? It makes lense callibration at positions of the card not in the center big challange - I can’t get less than 0.40 /plus or minus/ when the card is not on center position and on position 1 /center one/ I get 0.20 or less easy

[LightBurn (Oz)]

It is normal - another user here made themselves a helper for this:

Simple Aid For Focusing The Camera

I initially tried focus testing only using the honeycomb bed’s pattern as a focusing aid. At first I thought I got it right but then began to wonder if I could do better, so I printed out these five identical sheets of variable sized text and laid them out as shown below (taken with my phone, not the LB camera). [erase%2011] I was able to focus noticeably better. Everything is a compromise with these cameras. Specifically, the most beneficial thing was that I was able to get a good compromi…

[acho]

Exactly what I did. Will post image tomorrow