I just finished installing a new mirror and Rick Olsen's Brightscreen into my Rollei 2.8c Planar.
The old screen was dim and fairly difficult to see with uneven illumination. In bright sun I tended to use the magnifier to be able to see the screen.
I was hoping the Brightscreen would help with this but it made a *much* bigger improvement than I was expecting.
I took a few before/after shots out a window with a curtain in front of it.
The above is the stock screen shot at ISO200 1/60 f5.6. The picture is cropped to about the edge of the viewfinder but exposure was not adjusted in post.
Same basic distance away same ISO200 1/60 f5.6.
Same basic distance away ISO200 1/60 f8.
And then the same thing at f11.
Well worth the purchase.