Weird camera output when looking at emissive plane

I am trying to render an image of an emissive unlit plane from an orthographic camera in UE4. Unexpectedly, I found that the left and right sides of output images is dark due to some unknown effects. Then I rendered a white emissive unlit plane without any light source and get an image below:
Because the plane which my camera is looking at is unlit, I think the out put image should be totally white. However, it shows a “dark edges” effect. I was wondering if I can omit this effect and how.

Thanks in advanced!

hi Xuan402. Did you ever find a solution to this issue. I’m facing the same thing, and have not been able to fix it. I know that I can do the command “viewmode unlit” to fix it in editor, but this command is unavailable in release builds. In editor, you can hit F2 and F3 to switch between “viewmode lit” and “viewmode unlit” to see the issue. Really what I would like is to stay in viewmode lit, but to eliminate this darkening of the edges of the view. A material that is 100% unlit (to me), should ignore this kind of thing. I’ve attached an image demonstrating the problem

The edges are darkened with the Vignette effect from the Post Process Volume
It simulates how light takes longer to reach the corners of the image sensor/film of the camera so the edges end up darker than the center.

Add a post process volume, set it to Infinite Extent (Unbound) and then set Vignette Intensity to 0.