Nikon F4 K screen for cheap

[Farside]

I'd picked up a Nikon F4 recently and wasn't too keen on the AF focusing screen, so had a look at the alternatives. The K-series (split image) was available, but prices on them have gone silly.
However, I picked up an F3 K-series screen cheaply and today was able to fit that into the screen-holding frame of the F4.
It's a fiddly job, requiring a tiny JIS x-head screwdriver, but successfully accomplished.
The screen fits perfectly and focusing is entirely consistent with the old one, the Nikon green dot exactly co-inciding with the split image.

[visualopsins]

The method may be useful for upgrading other camera viewfinder focus screens.