My FE2 screen will darken in wrong light with f4 lenses.
If by this you mean the split image rangfider darkens try centering your eye in the eyepiece better. I didn't have much trouble with f/4.0 lenses. By f/4.5 the split image rangfider is showing you the barrel of the lens as it's trying to look through the edges of an f/3.5 or faster lens.
I remember well the A screen rangefinder blackout with my 80-200/4.5 Nikkor. The cure was an R screen or better an E or B screen. My camera then was an F2 or F2.
As I recall the R screen was like the A screen but the slope on the rangefinder was suitable for f/3.5 down to f/5.6 maximum apertures. It could be used with faster lenses with the risk of focus errors at apertures larger than f/3.5.
Dave Hartman