Vignetting with Intenscreen and WLF

I just received a Beattie Intenscreen for my RB67. I am getting significant vignetting when using the WLF. Not so when I use the prism finder. Any thoughts? The Intenscreen is unusable with the WLF as it stands. Any guidancd would be appreciated.

Thanks.

The screen has a fresnel lens in it that focuses the light. If you are viewing 'off center' it can get dark. I had an Inenscreen on a Rolleiflex 6x6 SLR but it was too hard to focus and I went back to the original screen.

That is the way they are.

Beatties have a very strong fresnel with a weak focus (diffusion) layer, and as a result, they were bright, but I found them hard to get acurate focus. The result of this also means that if your eye is any distance from the nodal point of the fresnel, you get visual vignetting. Try moving your eye farther away from the WLF until you get a clear view, that should be the nodal point. Prism finders typically have the nodal point at about 1m, which is much further back that when you peer into a WLF, especially with the magnifier.

Any lens collecting rays from the image made at a groundglass (as a fresnel) has to be (in its ideal state) to be apt for the exit cone of the lens as well as the situation behind the groundglass (eye or diopter).

There are no wonder-screens. The laws of optics dictate that to any benefit there will be a shortcome too.