You woudn't know I used to be a photographer!! The problem is a camera struggles to focus on something thats all white. There are no brush marks to see though - only the slight wood texture on the flat. What problems are you having with WB generally? A test like this is a bit of a cheat really because you start with new wood with a perfect surface and have control over the priming etc. You can also take time with it. But I didn't really need to try too hard with this - it levels really well without needing a lot of messing about.